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Home , Betulin, Birch bark, Cycloartenol, Diarylheptanoid, Digallic acid, Glucoside

EXTRACTIVES GENERAL FOREST PRODUCTS LABORATORY TECHNICAL FOREST SERVICE IN EASTERN REPORT U.S. DEPARTMENT OF - FPL 18 MADISON, WISCONSIN

A REVIEW 1979 SIGNIFICANCE OF COVER ILLUSTRATION (One example of how an extractive affected products)

Painted surfaces on the of slippery (Ulmus rubra) occasionally show yellow discoloration. Research at the U.S. Forest Products Laboratory has shown that this dis- coloration is due to a yellow extractive present in the outer heartwood. This extractive has been isolated in the form of brilliant canary yel- low needles. Its structure is identified as a new napthalenoid cadalenic . Left, surface painted gray showing bleedthrough of yellow stains; right, unfinished surface showing yellow streaks; center, crystals of yellow color- ing matter. SYNOPSIS This report extensively reviews the of extractives from wood and of hardwoods from the eastern United States. While such extractives are not used to a great extent commercially, they may in- fluence properties of the wood and perfor- mance of wood products. For example, extractives can protect wood from decay, add color and odor to wood, ac- cent grain pattern, and enhance strength pro- perties. Extractives may also inhibit setting of concrete, glues, and finishes; cause pro- blems in ; contribute to corro- sion of metals in contact with wood; present health hazards, and affect color stability of wood to light. Hardwoods in this review are grouped and discussed alphabetically by their respective botanical families. Grouping botanically makes it possible to draw chemotaxonomic inferences related to genera. Literature sear- ches cover 22 families and 174 ; species by family are listed at the beginning of each discussion section. TABLE OF CONTENTS

Page INTRODUCTION ...... 1 ACERACEAE (Acer spp., maples) ...... 9 AQUIFOLIACEAE (Ilex spp., ) ...... 11 BETULACEAE (Betula spp., ; Carpinus sp., hornbeam; Ostrya sp., hophornbeam) ...... 11 (Catalpa spp., catalpas) ...... 13 CORNACEAE ( spp., dogwoods) ...... 14 ( spp., ) ...... 14 (Fagus sp., ; and Quercus spp., ) ...... 14 HAMAMELIDACEAE (Liquidambar sp., sweetgum) ...... 20 HIPPOCASTANACEAE (Aesculus spp., buckeyes) ...... 21 JUGLANDACEAE (Carya spp., hickories; Juglans spp., butternut and ) ...... 22 LAURACEAE ( sp., sassafras) ...... 23 LEGUMINOSAE (Gleditsia spp., locusts; Robinia spp., locusts) ...... 25 MAGNOLIACEAE (Liriodendron sp., yellow-poplar; spp., ) ...... 26 MORACEAE (Maclura sp., Osage-orange; Morus spp., mulberries) ...... 31 NYSSACEAE (Nyssa spp., tupelos) ...... 36 OLEACEAE ( spp., ashes) ...... 36 PLATANACEAE (Platanus sp., sycamore) ...... 37 RHIZOPHORACEAE (Rhizophora sp., ) ...... 37 ( spp., plums and cherries) ...... 38 SALICACEAE (Populus spp., poplars, cottonwoods, and aspens; Salix spp., ) ...... 39 TILIACEAE (Tilia spp., basswoods) ...... 44 (Celtis spp., hackberries; Ulmus spp., ) ...... 45 EXTRACTIVES IN EASTERN HARDWOODS- A REVIEW

By John W. Rowe and Anthony H. Conner

Forest Products Laboratory,1 Forest Service, U.S. Department of Agriculture

INTRODUCTION Extractives are natural products extra- ates in the intermediary metabolic processes. neous to a lignocellulose ; they can be Thus most primary metabolites can be inter- removed with inert solvents such as ether, ben- converted in the organism into the other pri- zene-, , and cold . Al- mary metabolites via the intermediary meta- though cold water is considered inert, hot bolic processes. water will cause a slight, slow degradation of Typical primary metabolites include simple the lignocellulosic cell wall. Extractives may be , amino , simple , various car- within a cell wall, but are not chemically at- boxylic acids, and others. These will always be tached to it. Insoluble extraneous constituents found among the extractives of living , al- will include crystalline inclusions such as cal- though the amounts will vary depending on the cium oxalate and silica, as as gran- time in the growth cycle, the nutritional state, ules and certain polymeric materials. The ex- the , and the season. Reports of isolation tractives in eastern hardwoods range from 0.1 of these metabolites are of little taxonomic to 3.5 percent ether extractives, 0.9 to 6.5 per- significance. cent alcohol- extractives, and 1.3 to Secondary metabolites are generally com- 15.1 percent water extractives. Sequential ex- pounds more complex than the primary; tax- tractions will result in lower values for alcohol- onomic distribution is restricted and their for- benzene and water extractives. Because of this mation within the organism is essentially irre- extreme variability in extractives content, even versible. Thus secondary metabolites express within different pieces of wood from the same individuality of a species in chemical terms. Fig- , analyses of the cell wall constituents of ure 1 illustrates the general secondary path- wood and bark are always carried out on ex- ways that bring about this type of extractives in tractive-free wood. eastern hardwoods. can be consid- Extractives are from two general sources. ered the primary product of The first source is the compounds involved in a and is the starting material for producing cell tree’s metabolic processes; the second is arti- wall components and most secondary facts from further modification of metabolites metabolites. by means other than metabolic processes of a Although in the broadest sense, all sec- tree or from external sources. ondary metabolites are taxonomically signifi- The extractives formed from a tree’s meta- cant, certain secondary metabolites are appar- bolic processes can be divided into two general ently ubiquitous to hardwoods and in the con- categories-primary and secondary metabo- text of this Review are not taxonomically lites. The primary metabolites are the bio- organic compounds that occur in essentially all 1Maintained in cooperation with the University of Wisconsin- organisms and that constitute the intermedi- Madison.

-1- -2- significant. All hardwoods thus possess the en- aceae, and Magnoliaceae). zymes necessary for producing these com- The remaining types of extractive found in pounds. To a large extent these compounds trees are artifacts. They can arise from many are intermediates rather than final products of sources, none of which involves a tree’s en- . In some species or tissues these zyme systems. Some may be metabolites of mi- intermediates accumulate in pools that are iso- cro-organisms; apparently sound wood on lable in large quantities, whereas in others they careful investigation is often found to contain are metabolized further as fast as they are micro-organisms. Some extractives reported formed, thus are isolated with difficulty, in only from tree barks may actually be lichen metabo- small amounts. Further, these pools of inter- lites. But the most important artifacts are those mediates may be limited to specific tissues or formed by autoxidation and nonenzymatic free by specific conditions; thus this accounts for radical or -catalyzed condensations. These their variability. Examples of secondary metab- reactions are particularly common among the olites common to all hardwoods include starch, polyphenolic heartwood extractives. Thus the sitosterol, simple , , color in is probably predominately an , the common , artifact. Similarly, the low decay resistance of simple tannins, and probably compounds such central heartwood of many species results with as (see Fagaceae) that are men- time from polymerization of toxic phenolics tioned repeatedly throughout this Review. caused, for example, by the acidity from anaer- Many secondary metabolites have a more obic bacterial attack. restricted distribution than do the primary be- Aromatic compounds are formed bioge- cause not all biogenetic pathways are opera- netically either from acetate via malonyl CoA to tive in all species or tissues and they may ter- give the aromatic “acetogenins” or directly minate at different stages. These metabolites from glucose via the pathway. In may be characteristic of a family, a genus, a some instances, e.g., the flavonoids and stil- subgenus, a section, a subsection, a species, benes, different parts of the same are or even a chemical race within a species. They derived via both pathways. Figure 2 shows in form a basis for chemotaxonomy because they detail the biogenesis of simple aromatic com- reflect in part the systems that pro- pounds via the shikimic acid pathway and their duced them, thus the genetic makeup of a tree. conversion into and the other common However, the expression of these may phenolic extractives obtained from eastern be controlled by environmental factors includ- hardwoods-hydrolyzable and condensed tan- ing season, nutritional state, the particular tis- nins, flavonoids, , and . The sue being discussed, and if a tree is under at- coumarins and their apparently are tack by decay organisms that will elicit wound important in regulating the enzymes in a tree response reactions. Thus chemotaxonomic (153). Tannins are used in the studies based on the relative amounts of var- for converting skins into a stable leather ious metabolites can be highly misleading if the product by their ability to form multiple hydro- sample is insufficient to warrant statistical gen bonds with . Most water-soluble treatment. Chemically these secondary metab- in the molecular weight range 500 olites will often be end products of metabolism, to 3,000 have this property. Thus tannins are and will be more elaborate and complex than capable of precipitating enzymes; and can de- those common to all hard . These are toxify microbial digestive enzymes as well as in- among the most interest-provoking of the ex- terfere with the activity of isolated organ- tractives of trees, examples of which are the al- elles. They are markedly and have kaloids (Magnoliaceae and Lauraceae), com- been implicated in initiating esophageal cancer plex flavonoids (Moraceae), complex monoter- (228). The early literature on tannins must be penes (Bignoniaceae), treated with caution. was often consid- (Magnoliaceae, Ulmaceae), acetogenins ered as the amount of hot-water extract if this (Ebenaceae and Juglandaceae), glyco- extract was capable of precipitating gelatin or sides (Salicaceae), complex coumarins (Acer- being precipitated by heavy metals, , aceae), cyanogenic glycosides (Rosaceae), or acidified . The percentage of and other complex phenolics (Moraceae, Laur- tannin should be accompanied by the percent-

-3- Figure 2.–Aromatic compounds derived from glucose.

M 146 009 age purity of the tannin determined by the frac- of (+)- and its 3-epimer (-)-epicate- tion of the hot-water extract absorbed by chin, as a result they yield if treated chromed powder. with acid. Corresponding derivatives possess- tannins may be divided structur- ing a 3´,4´,5´-hydroxylation pattern [(+)-gallo- ally into two types: Hydrolyzable tannins and catechin, (-)-epigallocatechin] yield the corre- condensed tannins. Hydrolyzable tannins are sponding on treatment with acid. characterized by having a polyhydric alcohol, A-2 is illustrated in the predominately glucose, partially or wholly es- Hippocastanaceae and the catechin dimer terified with , hexahydroxydiphenic (proanthocyanidin B-3) and trimer (proantho- acid, and their derivatives. Tannins with this cyanidin C-2) in Figure 3. Further polymeriza- type of structure can be readily hydrolyzed by tion leads to higher oligomers of -3,4-diol acids or enzymes to give the carbohydrate and flavan-3-ol principally responsible for the moiety and the moieties such as properties usually attributed to the true tannins. gallic acid and (the dilactone of Eventually, polymerization leads to the high- hexahydroxydiphenic acid). Therefore these molecular-weight that are insol- tannins are also called or uble. Still higher molecular weight polymers, . such as the red powder that drops out if labo- Condensed tannins are polymers ratory corks are rolled to soften them, are prob- that contain only phenolic moieties and give no ably the backbone on which suberin is laid in significant amounts of low-molecular-weight the formation of . Therefore, the cork frac- compounds on . These tannins in- tion of bark consists of a three-dimensional net- stead tend to polymerize further in acid work of insoluble polyflavonoids, together with to give insoluble, amorphous, colored phloba- polyestolide fats and (suberin). Although phenes. Figure 3 outlines the general bioge- largely insoluble in inert solvents, suberin can netic interrelationships among the various be dissolved by hot, dilute alkali to yield mono- types of flavonoids and the condensed tannins. meric fatty and compounds, and a polyfla- The precise biosynthetic pathways have not vonoid “phenolic acid” that results from rear- been fully elucidated (138). The interrelation- rangement of the flavonoid nucleus (311). Pure ships are illustrated using the oxida- phenolic polymers are colorless, but the tan- tion pattern that apparently is the most com- nins found in nature are normally colored, pre- mon although many other hydroxylation pat- sumably due to oxidation to extended, conju- terns are known (the Leguminosae and gated systems such as that shown in Figure 3 Moraceae). Quercetin, a common extractive or to o-quinones. The condensed tannins and from hardwoods, and related compounds was related polyflavonoids are extremely common recently shown to have mutagenic activity (35). extractives, especially in bark. Roux has written O- and C-glycosylated flavonoids are also an excellent review of this subject (299) and found in the eastern hardwoods as are a variety Harborne has discussed the relationship be- of methyl ethers and a few alkyl derivatives. The tween flavonoids and the evolution of the an- (the glycosylated derivatives of giosperms (131). the ) contribute to the beautiful Outlined in Figure 4 is the general biosyn- colors of autumn of hardwoods (140). thetic relationships of the compounds derived The also occur as glyco- from acetate (i.e., acetyl CoA) via the interme- sylated derivatives, the leucoanthocyanins. diacy of . These pathways are The leucoanthocyanins and leucoanthocyani- responsible for formation of the , dins are the colorless precursors of the antho- sesquiterpenes, diterpenes, , and cyanins and anthocyanidins. . (i.e., ) are ubiqui- The flavan-3,4-diol () tous in the plant kingdom. The most common of and flavan-3-ol precursors of the condensed these is sitosterol (24-ethylcholesterol) that al- tannins polymerize first into a wide variety of ways co-occurs with lesser amounts of its lower dimeric and trimeric homologs, and , and (19, 138, 139, 354, 372) with diffrerent types of minor amounts of their saturated counterparts, linkages between the flavonoid groups. The stigmastanol, campestanol, and cholestanol. proanthocyanidins are predominately polymers The co-occurrence of these six sterols sug-

-5- -6- -7- gests that the hydrogenase enzyme that re- also tend to contain the various gums, kinos, duces the side-chain double bond is not com- and balsams that have evolved as part of the pletely stereospecific. In this Review, β-sitos- wound response mechanisms, as well as the terol is taken to represent the sitosterol-rich compounds capable of protecting these meta- mixture of sitosterol and campesterol, whereas bolically inactive tissues against biological γ-sitosterol is the campesterol-rich mixture of attack. sitosterol and campesterol (355). Various other Apparently eastern hardwoods evolved sitosterols have been reported in early litera- earlier than did tropical angiosperms. There- ture. α1-Sitosterol has been shown identical to fore it is not surprising that extractives of east- the citrostadienol (18) that is always ern hardwoods are generally less complex and accompanied by small amounts of its lower less likely to contain compounds with signifi- homolog, 24-methylenelophenol. The α2- and cant physiological activity. α3-sitosterols are now known to be mixtures The most intriguing extractives are those rich in cycloartenol and its derivatives. Many compounds that can be used as chemotaxon- other sterols are known that are intermediates omic markers and the compounds that can be between the initially formed cycloartenol and correlated with some specific property of a the last-formed , , but in most wood such as decay resistance or color. cases these do not accumulate and are metab- The species included in this Review are the olized as rapidly as they are formed. Unlike the eastern hardwoods listed in Little’s Atlas (207) other sterols often found in the form of plus other representatives of the same genera of fatty acids, stigmasterol usually is found pre- that will be listed in a forthcoming volume of Lit- dominately unesterified. tle’s Atlas that includes rare eastern hard- Wood and bark extractives from eastern woods. A booklet that briefly describes the im- hardwoods of the United States are not used to portant trees of the eastern forest has been any great extent commercially. Extractives are prepared (234). The hardwoods in this Review nevertheless important in the utilization of east- are grouped and discussed alphabetically by ern hardwoods because of their contributions their respective botanical families. Grouping to the properties of wood. The extractives can botanically makes it possible to draw chemo- protect wood from decay, add color and odor taxonomic inferences relating to genera. Liter- to wood, accent grain pattern, and enhance ature searches cover 22 families and 174 spe- strength properties. In contrast, they can con- cies; species by family are listed at the begin- tribute to of metals in contact with ning of each discussion section. The literature wood; inhibit setting of concrete, glues, and fin- on the extractives of wood and bark has been ishes; cause various problems during - thoroughly covered. The chemistry of special- making; present health hazards (e.g., dermati- ized tissues such as leaves, , , and tis, asthma, and cancer); and affect the color can be quite different and is not men- stability of wood to light. Seldomly can all of the tioned except if of special interest or if very little color from wood or bark be removed by extrac- information is available. Although there are tion because of polymerization of the extrac- many publications on the extractives of hard- tives into insoluble deposits as discussed for woods of the eastern United States, most spe- the tannins. cies have not been investigated and most of the Inner bark and sapwood generally are rich species investigated have received only limited in simple monomers and nutrients such as fats, attention. In only a few have studies been ex- starch, , simple sugars, inositols, sim- tensive enough to provide understanding of the ple glycosides, free and esterified sterols, and chemistry of the extractives. phenylpropanoids and other simple phenolics. Locating information on extrac- Heartwood and outer bark, by contrast tend to tives in technical abstracts is difficult because be deficient in nutrients, glycosides and meta- this material is published in a wide variety of bolic intermediates, but are rich in compounds journals, all compounds isolated are not in- such as hydrolyzable and condensed tannins dexed, all species are not indexed by scientific and many other phenolics, alkaloids, , es- name, changes have been made in botanical sential oils, and specialized compounds of a names or synonyms are used, and several com- wide variety of types. Heartwood and outer bark mon and systematic names for individual natu-

-8- ral products are used. A recent three-volume ing supplements. Other useful references are work “” (222) is a good general “Konstitution and Vorkommen der organ- reference. Specialized information is available ischen Pflanzenstoffe” (177) and the “Hand- in the annual “Recent advances in phytochem- book of naturally occurring compounds” (80). istry,” the proceedings of the annual sympos- Many specific types of natural products are re- ium of the Society of North viewed in monographs: Alkaloids America. The “Lynn index” (103) of which (212,295,375,376), terpenoids (236) organic eight volumes have now been published, con- acids (41) flavonoids (116,133,210), and ste- tains brief coverage of plant components re- roids (104). One book concentrates on the ported to 1954 and listed by species. Future chemistry of wood extractives (148). A recent volumes will index the chemical constituents. report discusses the chemistry of the extrac- More up-to-date is the excellent series “Chem- tives of bark (134). otaxonomie der Pflanzen” (143). The index in- This Review will be limited to the chemistry cludes both species and compounds. The four- of bark and wood. Most of the source material volume series “Chemotaxonomy of flowering is derived from the authors’ files. References to ” (118) also contains useful information early results satisfactorily covered in second- and is indexed by species and compounds. An ary sources generally are not included. Data on excellent reference on structure and source of amounts extractable with various solvents are a is the “Dictionary of organic also omitted because of great variability in compounds” (288), five-volumes plus up-dat- values.

ACERACEAE

Acer barbatum Michx., maple parently is ubiquitous in the Aceraceae (143). A. leucoderme Small, chalk maple In a study of the water-soluble polysaccharides A. negundo L., boxelder of the sapwood, heartwood, and inner bark of A. nigrum Michx. f., black maple maple, the major component in each tis- A. pensylvanicum L., striped maple sue was found to be glucomannan, 4-O-meth- A. rubrum L., red maple ylglucuronoxylan, and arabinogalactan, re- A. saccharinum L., silver maple spectively (8). A. saccharum Marsh., sugar maple Tannins apparently are not present in ma- A. spicatum Lam., mountain maple ple wood, although the barks reportedly con- The literature on maples to 1961 has been tain relatively small amounts of them: Black ma- ably summarized (143); a review in 1970 (197), ple, 1.9 percent; red maple, 6.9 percent; silver added little. maple, 2.8 to 7.8 percent; sugar maple, 0.4 to The maples, especially black and sugar 2.7 percent (304). An acertannin, isolated in 0.6 maples and to a lesser extent red and silver ma- percent yield from mountain maple bark and ples, are best known for maple sirup produced assumed typical of the tannins from maples, by boiling down the (378); this was an art was 3,6-di-O-galloyl-1,5-anhydrosorbitol (fig. taught to the early settlers by the Indians, who 5). The of boxelder and also used maple bark and the rotted wood as a sugar maple barks has been investigated (55). dyestuff. Boxelder wood and bark contain essentially no Maple sap consists primarily of sucrose tannin. and an arabinogalactan (9). Other constituents A chemical comparison of clear and min- include quebrachitol (2-O-methylinositol) eral-stained sugar maple has been made (244,340) phytokinins (237) two trisaccharides (196,198). Peracetic acid and sodium chlorite (128) glucose, fructose, allantoin, allantoic will bleach mineral stain in sugar maple (199). acid, , , syringaldehyde, Gallic acid and catechin are the main phenolics , malic acid, coniferyl alcohol, coni- in the clear wood of both red and sugar maples feraldehyde, and guaiacol. Quebrachitol ap- (343). Significantly, these are both absent in

-9- Figure 5.–Tannin from mountain maple (Acer spicatum) bark. Figure 6.– fraxetin derivatives iso- lated from sugar maple (Acer saccharum)

M 146 162 wood. M 146 163 discolored or decayed wood. The color cannot acid, and proanthocyanidins; boxelder wood be completey extracted from this type of dis- and bark contain mannitol, glucose, galactose, colored wood. Presumably, the phenolics have and arabinose (316). been oxidatively polymerized. In a search of the Among the most pharmaceutically inter- precursors of this color, a closely related series esting of the extractives in maple are the tumor- of fraxetin derivatives (fig. 6) was isolated in 1 inhibiting of boxelder leaves and percent yield from mineral-stained sugar maple stems (191). The aglycone of P has wood (213); they are absent in clear wood. been shown to be a mixture of trans (acerotin) These are antifungal and are apparently pro- and cis (acerocin) isomers of diesters of the duced by the tree in response to stress. new triterpene, acerogenic acid (fig. 7). The Red maple wood and bark have been aglycone of saponin Q has been shown to be a found to contain glucose, β-sitosterol, D-cate- similar of 24-hydroxyacerogenic acid. chin, and a consisting of leuco- One of these aglycones may be the unknown cyanidin units linked 4-8 (233,316). However, triterpene isolated along with β- the procyanidin from the wood was a dimer, sitosterol and sitosterol-D- from in- whereas that from the bark was a trimer. The sect-infected boxelder wood (183). bark also contains pyrogallol and gallic acid. The bark of red and mountain maple (187) are Figure 7.–Aglycones of tumor-inhibiting sa- used in folk medicine as an , tonic, ponins isolated from boxelder (Acer and opthalmiatric. Maple-bark disease is a pul- negundo). M 146 164 monary hypersensitivity reaction to the fungus Cryptostroma corticale, it is marked by cough, and night sweats, and radiographic evidence of infiltration (386). Sugar maple wood and bark yielded β -sitosterol and a small amount of leu- coanthocyanidins (316). Coniferaldehyde and sinapaldehyde are present in the wood (36). Sil- ver maple bark contains β -sitosterol, gaIIic

-10- AQUIFOLIACEAE llex ambigua (Michx.) Torr., Carolina for diabetes, gout, smallpox, and to expel kid- I. amelanchier M. A. Curt, juneberry holly ney stones (226). During the Civil War the I. cassine L., dahoon leaves of American holly were a common sub- I. coriacea (Pursh) Chapm., large gallberry stitute in the south for imported tea. The leaves I. decidua Walt., possumhaw of yaupon were used to prepare a tea for similar I. krugiana Loes., tawnyberry holly uses by the Indians in the Southeast. I. laevigata (Pursh) A. Gray, smooth An investigation of American holly leaves winterberry and showed that the extract of the I. longipes Chapm., Georgia holly leaves, but not the fruit, was lethal to mice and I. montana Torr. and Gray, mountain hemolytic to human erythrocytes (373). The winterberry toxic substance in the ethanol extract could not I. myrtifolia Walt., myrtle dahoon be characterized. However, the extract was I. opaca Ait., American holly shown to contain a crude sa- I. verticillata (L.) A. Gray, common winterberry ponin that was not toxic but was hemolytic to I. vomitoria Ait., yaupon erythrocytes. Nonacosane was isolated from a Although the literature on hollies to 1963 nontoxic hexane extract of material, and has been ably summarized (143) essentially from the nontoxic ether extract of nothing is known about the extractives of east- the ripe fruit. ern hollies. Neither the wood nor the bark ap- Most recent reports in the literature on the parently contains more than traces of tannins. chemistry of holly are on leaves and bark of That the wood is white, susceptible to decay, Japanese hollies, which have been investi- and permeable suggests that the extractives gated extensively. Birdlime, the sticky ether ex- have no significant function for this genus. This tractables of the bark of Japanese holly used to genus is best known for the decorative Christ- ensnare small birds, is rich in pentacyclic triter- mas holly. pene esters, and the Chinese have found that In South America tea is prepared triterpene saponins in the bark have antimalar- from the leaves of Ilex paraguariensis. A mild in- ial properties (64). The bark of American hollies fusion is innocuous, but a stronger brew is an probably contains similar materials. emetic and a . At one time it was given

BETULACEAE

Betula alleghaniensis Britton, yellow source of methyl salicylate, was important in B. lenta L., sweet birch commerce before synthetic methyl salicylate B. nigra L., river birch became readily available. The methyl salicylate B. papyrifera Marsh., paper birch is formed from the 6-xylosidoglucoside of B. populifolia Marsh., gray birch methyl salicylate if the bark is hydrolyzed with Carpinus caroliniana Walt., American hot water. The American Indians obtained a hornbeam birch tea, a red dye, and a decoction to treat Ostrya virginiana (Mill.) K. Koch, eastern bruises and cuts from . They chewed hophornbeam the inner bark, which is especially sweet and The extensive literature on the birches to spicy in spring, and obtained sugar from the 1961 has been summarized (143). A review in spring sap for food. 1970 (197) added little additional information. Tannins apparently are not present in birch The most studied birch is, of course, sweet wood. However, the barks contain relatively birch, the bark of which was a source of oil of small amounts of tannins: Paper birch, 1.6 to sweet birch (103,143). The oil, an excellent 3.3 percent; yellow birch, 1.5 to 4.4 percent;

-11 sweet birch, 3.5 percent; river birch, 5.6 per- These triterpenes in the wood may contrib- cent; gray birch, 2 to 5 percent (304). Tannins ute to the yellowing of bleached birch (24) are highest in barks of birches with dark-col- and are certainly major components of the un- ored bark. The general chemistry of yellow and saponifiables. Thus one-third or more of the paper birch bark has been studied (55); a little ether extract of paper birch (44,45,67,231) is more than 5 percent of formaldehyde-reactive unsaponifiables consisting of triterpenes, ster- tannin was present in the bark of each species. ols, , and related compounds. More A major characteristic of paper and gray than one-half of the ether extract is esters of birches is the white bark. A white powder, fatty acids. Of these, 90 percent is triglycerides which has been reported to cause skin erup- and 4 percent sterol esters. Linoleic acid is the tions in mill workmen (386) can often be re- predominant acid in the esters. Small amounts moved from the surface of these barks. The of free fatty acids and free triterpene acids such powder consists mostly of nontoxic pentacyclic as betulinic and oleanolic acids are also pres- lupane triterpenes, characteristic major com- ent. Citrostadienol (18) was isolated from Eu- ponents of birch barks (fig. 8). Paper birch bark ropean silver birch wood (25,205) and is un- contains 1.5 percent (317). Other triter- doubtedly identical to the sterol indicated pres- penes present are , , olean- ent in paper birch wood (44). The fatty acids in olic acid and acetyloleanolic acid as well as β- yellow birch wood are similar to those in paper sitosterol and a procyanidin. The heartwood birch (67). This pattern is probably typical of the contains similar components, namely betulin, nonpolar extractives of all birch wood, and is in lupeol, β -sitosterol, and a very small amount of agreement with the extensive research on Eu- procyanidin (317). Sweet birch bark contains ropean silver birch (25,174,175,245,246). Silver lupeol and betulin as major constituents with birch is often added to kraft cooks of soft- lupenone, oleanolic acid, β -sitosterol, methyl woods; the adverse effect of the added birch on salicylate, and ; the heartwood the yield and the composition of the has contains lupeol, betulin, methyl acetylbetuli- been of interest (152). The decrease in surface nate, methyl salicylate, β-sitosterol, sitosterol- wettability of yellow birch on heating has been β -D-glucoside, and a small amount of a pro- explained by autoxidation of the esters of lino- cyanidin (316,317). Yellow birch bark contains leic acid esters (145). Acetone of the lupenone as the major constituent with betulin, surface prevented this decrease. lupeol and procyanidin. The heartwood con- A group of neutral terpenoids isolated on tains betulin, lupeol, lupenone, methyl acetyl- saponification of the fatty esters of European betulinate, β -sitosterol, sitosterol-β -D-gluco- silver birch is the betulaprenols (fig. 4) side and trace of procyanidin (316,317). (123,205). They consist of long-chain aliphatic unsaturated (polyprenols). Al- though they have not been reported in eastern American birches, their occurrence is probably widespread. Thus, a fraction isolated from pa- per birch wood (44) is probably betulaprenols. The chemistry of polyprenols has been re- viewed (144). Paper has been used to analyze the alcoholic extracts of the inner bark of paper birch and one of its hybrids, but only chlorophyll was identified (86). A pectic acid isolated in 4.5 percent yield from the inner bark has been shown to be 4-O-methylglucuronox- ylan (356). Paper birch sap has been found to contain an arabinogalactan, D-glucose, D-fruc- tose, sucrose, gentiobiose, melibiose, manno- Figure 8.–Triterpenes from birch barks. triose, verbascotetraose, and two trisacchar- ides (129) as well as a complex polysaccharide M 146 165 (360). Catechin and glycosides of pyroca- -12- techol, coniferyl alcohol, and pyrogallol were nothing else is known about the chemistry of found in the heartwood of paper birch. It is pos- the wood and the bark of these two species, al- tulated that the reddish-brown stain in the though in the early literature, the chemistry of heartwood is produced by fungal phenol oxi- these genera is mentioned briefly (103,143). dases acting on these compounds (322). The This suggests that the chemistry of these two wood reportedly causes dermatitis (314). species might be of interest because in recent The distribution of gum in yellow birch has years Japanese hophornbeam has been found been studied via scanning electron microscopy to contain a series of homolignans with a bi- to elucidate how it affects properties of the phenyl linkage (388). Similar wood (185). have been reported in Betula platyphylla var. ja- The woods of American hornbeam and ponica (346) and six (Betulaceae) eastern hophornbeam contain no tannins, al- (176,238,341,345,361). The hornbeams are though the barks contain 3.7 to 4.8 percent and considered by some authorities to be members 4.1 percent, respectively (304). Essentially of the Corylaceae.

BIGNONIACEAE

Catalpa bignonioides Walt., southern catalpa found in different parts (especially the fruit) of C. speciosa Warder, northern catalpa several members of this genus; in 1888, it was Although the extractives chemistry of the found in southern catalpa bark (143). Because Bignoniaceae to 1962 has been reviewed it is also reported in northern catalpa fruit, it (103,143), almost nothing on the wood and the presumably is also present in this bark. How- bark extractives of southern and northern ca- ever, catalposide has not been reported in the talpa has been reported in the last 20 years. wood from any eastern catalpas. Southern ca- Neither the wood nor the bark of northern ca- talpa bark also has been reported to contain talpa contains tannins (304). The water extrac- another heteroside called catalpinoside (het- tives of northern catalpa are quite variable erocatalposide) (143,287). The most recent (167); cold-water extractives from the heart- work on this genus has been studies on Japa- wood range from less than 2.7 percent in the nese Catalpa ovata wood, which yielded β-si- summer to more than 7.5 percent in the spring. tosterol, cerotic acid, a series of simple pheno- The wood and the bark of southern catalpa lics and carbohydrates (165) a new phthalide accumulate remarkable amounts of stachyose (catalpalactone), and six prenylated naphtho- (9.3 pct and 5.4 pct, respectively) as well as quinones (166,321). These naphthoquinones lesser amounts of sucrose, raffinose, and per- are quite similar to the extractives characteris- haps verbascose (143). tic of Streptospermum, Tabebuia, and other The most interesting extractive chemotax- genera of the Bignoniaceae, and suggest that onomically in the catalpas is the noriridoside, further studies on the extractives of northern catalposide (catalpin) (215) (fig. 9). It has been and southern catalpa wood should be conducted.

Figure 9.–lridoid monoterpenes. M 146 166

-13- CORNACEAE

Cornus alternifolia L. f., alternate-leaf tannins (232). Flowering dogwood has been re- dogwood ported to contain no tannin in the wood but 3.3 C. drummondii C. A. Meyer, roughleaf percent in the bark (304). The bark contains the dogwood interesting (fig. 9) cornin () C. florida L., flowering dogwood (46). A closely related compound, dihydrocor- C. racemosa Lam., gray dogwood nin in which the keto group has been reduced, C. rugosa Lam., round-leaved dogwood has been isolated from the leaves and twigs C. stolonifera Michx., red-osier dogwood (171). C. stricta Lam., stiffcornel dogwood The leaves of dogwood are an irritant but Present information on the chemistry of there are no reports of ill effects from the wood the dogwoods is predominately limited to the (386). A folk remedy for chills and fever was a leaves (143). The proteins in red-osier dog- potion of whiskey in which the inner bark of the wood have been studied (164) and the bark flowering dogwood was steeped until all bitter- has been found to contain hyperin (quercetin- ness had been extracted (226). The Indians 3-), fumaric acid, wax esters, and also used this bark as a tonic and a stimulant.

EBENACEAE

Diospyros texana Scheele, The paucity of information about persim- D. virginiana L., common persimmon mon contrasts sharply with the abundance of Of the eastern persimmons, only the ex- published material on the extractives of the tractives of the common persimmon have been many other Diospyros species, which include investigated. A red pigment, isodiospyrin, has the African and the Asiatic ebonies. The litera- been isolated from the wood and bark (102). ture to 1964 has been reviewed (143). A few of Another quinone, which may be a hydroxyl de- the significant publications on the extractives rivative of isodiospyrin, was also isolated from of other Diospyros species (200-203, the bark. 230,342,347,365) confirm the general pattern 7-Methyljuglone was identified recently as that the wood and the bark of this genus are the major termiticial component of wood of characterized by pentacyclic triterpenes and Diospyros virginiana (52). lsodiospyrin was also derivatives. Although these deriv- toxic to termites but to a lesser extent than 7- atives include napthols, naphthaldehydes and methyljuglone. Shinanolone and scopoletin napthoic acids, the most predominant com- (see Fagaceae) were also found in the wood pounds are the naphthoquinones (fig. 10). Di- but were not detrimental to termites. mers with extended conjugation are common The freshly cut sapwood can discolor from and even trimers have been reported. Foreign air oxidation of the extractives (309); this can Diospyros species have been reported to cause be prevented by steaming. The early literature severe allergies, presumably from the various conflicts; either 0 or 8.5 is reported as the per- quinones (386). The chemistry of Texas and centage of tannin in common persimmon bark. common persimmon extractives apparently The wood, however, does not contain tannins. may be worthwhile to research.

-14- Figure 10.–Napthoquinone derivatives from Diospyros species.

M 146 172

FAGACEAE

Fagus grandifolia Ehrh., American beech The literature on the Fagaceae to 1964 has Quercus alba L., white been reviewed (103,143). However, almost all Q. arkansana Sarg., Arkansas oak research on the extractives of beech has been Q. bicolor Willd., swamp white oak on the European , the sap of Q. chapmanii Sarg., Chapman oak which is well known to cause dermatitis (386). Q. coccinea Muenchh., scarlet oak Although the sapwood of American beech may Q. durandii Buckl., Durand oak contain up to 4 percent total extractives, the Q. ellipsoidalis E. J. Hill, northern pin oak heartwood contains less than 2 percent (167). Q. falcata Michx., southern red oak The wood does not contain tannins (304) Q. georgiana M. A. Curtis, Georgia oak whereas the bark contains only 2.4 percent Q. havardii Rydb., Havard oak (143). Extrapolating what is known about the Q. ilicifolia Wangenh., bear oak rather ordinary extractives of other as Q. imbricaria Michx., shingle oak well as those of other members of this family Q. incana Bartr., bluejack oak plus the low level of extractives present sug- Q. laceyi Small, Lacey oak gests this would not be a rewarding species to Q. laevis Walt., turkey oak examine. The bark is probably rich in the usual Q. laurifolia Michx., laurel oak suberin components and pentacyclic triter- Q. lyrata Walt., overcup oak penes; the inner bark, in the usual simple sug- Q. macrocarpa Michx., bur oak ars, fats, and steroids; and the heartwood prob- Q. marilandica Muenchh., blackjack oak ably contains a broad array of relatively simple Q. michauxii Nutt., swamp oak phenolics. Q. mohriana Buckl., Mohrs oak The oaks not only include the largest group Q. muehlenbergii Engelm., chinkapin oak of species among the eastern hardwoods, but Q. myrtifolia Willd., myrtle oak also constitute more than one-third of the total Q. nigra L., water oak growing stock of eastern hardwoods. The oak Q. nuttallii Palmer, Nuttall oak bark formerly employed for internal and exter- Q. oglethorpensis Duncan, Oglethorpe oak nal pharmaceutical purposes was that of white Q. palustris Muenchh., pin oak oak. Because the bark contains tannins, it has Q. phellos L., oak been used as an astrigent and an . A Q. prinoides Willd., dwarf chinkapin oak bark tea is used in Appalachia to treat burns Q. prinus L., chestnut oak and sore throat (187). Red oak bark has been Q. rubra L., northern red oak used to treat dysentery, pulmonary and uterine Q. shumardii Buckl., Shumard oak hemorrhage, and intermittant fever (226). Q. stellata Wangenh., oak Oaks are well known for the tannins iso- Q. velutina Lam., black oak lated predominantly from the bark (141,142). Q. virginiana Mill., live oak Values for the tannin content of the oaks com-

-15- piled from various sources are given in Table 1. (also in Fagaceae), which has been almost ex- Chestnut oak bark is known to be a satisfactory terminated by chestnut blight. source of tannin. Blackjack, southern red, and Oak barks contain D-catechin and D-gal- black oak barks apparently have commercial locatechin, , leucocyanidin, potential (22). Although any tannin content , gallic acid, and various con- above 8 percent suggests commercial poten- densed tannins based on catechin-gallocate- tial, various other factors must be considered. chin polymers. The structures of seven differ- The purity of the tannins, the stability of the so- ent dimers in European oak bark have been elu- lutions, the color of the resultant leather, and cidated, as more recently has the structure of a the reactivity with formaldehyde (for use in ad- catechin trimer (fig. 3) (10). Compounds such hesives) affect commercial potential. The yield as these are probably common in all barks con- may be considerably increased if extraction is taining condensed tannins. In contrast to the with aqueous sodium sulfite (95). This results in condensed tannins that predominate in the part from sulfonation, which increases solubil- bark, hydrolyzable tannins predominate in oak ity, and in part from the alkaline degradation of wood. The gallotannins and the ellagitannins the high-molecular-weight polymeric flavon- isolated from European oak have been exten- oids in cork to soluble so-called bark phenolic sively studied, and many individual structures acids. The mechanism of this degradation has determined (219). The series of natural prod- been elegantly elucidated (311). Oak is not now ucts most difficult to study among eastern a commercial source of tannin in the United hardwood extractives is the complex mixture of States. The last significant domestic produc- individual condensed tannins in the bark and tion of tannin was from the the individual hydrolyzable tannins in the wood.

Table 1 .–Tannin content of oak wood and bark

Oak Percent tannin in Wood1 Bark Black I 5.6, 8.4, 6-12, 9.2-9.3 (av) 58% pure (22) Blackjack I 7.7, 8.8-9.2 (av) 64% pure (22) Bluejack I 7.7, 6.7, (av) 56% pure (296) Bur 4.6, 5.6 Chest 3.3 6.25, 7.2-11.1 (143) 10.8, 10-12, 8-14, 153-16.0 (av) 63% pure (22) Chinkapin 5.2 4.8 Dwarf chinkapin 4.3-10.3 Laurel I Live 6.9 4.0, 10.5 Northern red 1.8, 2.5 4.6, 5.5, 5.4-11.1, 10.9, 5.4-6.4 (av) 53% pure (22) Overcup 0, I 6.5 Pin 0 4.3, 7.6 Post 2.9, 5.4 2.3, 3.1, 7.1-7.4 (av) 59% pure (22) Scarlet 0 6.6, 6-8, 7.7, 7.1-10.6 (av) 58% pure (22) Shingle 1.6 3.8 Shumard 0, 3, 1 4.3, 5.2 Southern red 0, 1.8, 2.0 6.4-8.7, 8.6, 10.0, 9.7-9.9 (av) 67% pure (22) Swamp chestnut 3.1 9.1 Swamp white 14.2 Turkey 2.4 10.5 (av) 59% pure (298) Water 1.0 4.3, 4.6, 7-8 White 2.7 2.3, 6, 6.3, 5.1-7.2, 7, 7.9, 6.1-6.6 (av) 57% pure (22) Willow 0, I 7.3, 10.1 1 I, Insignificant

-16- Commercially cork is derived primarily The extractives were shown to contribute to the from the bark of the Mediterranean cork oak, Q. dimensional stability of the wood (320). Figure suber, if grown slowly on dry poor . The in- 12 shows the result of a two-dimensional paper numerable studies on this complex of highly chromatogram of the sapwood and the heart- polymerized flavonoids and estolide waxes wood acetone-water (95:5) extractives (313). have been reviewed (69,195). Cork is, of The contrast between the components of the course, the original source of the pentacyclic sapwood and the heartwood is particularly triterpenes, friedelin and cerin (fig. 11), and oak noteworthy. Hydrolyzable gallotannins such as barks have been found to contain more than 12 hamamelitannin [5-galloyl-2-(galloylhydroxy- triterpenes with friedelane, glutinane, ursane, methyl)-ribofuranose] and ellagitannins pre- oleanane, lupane, and dammarane skeletons. dominate, and are also the main components in Also common are various soluble waxy com- the more polar acetone-water (1:1) and water ponents, sterols, and esters such as lignoceryl extracts. In addition to the compounds listed, ferulate. the sapwood contains leucoanthocyanins and Black oak inner bark ( bark) con- possibly (fig. 2). m- ap- tains the simple flavonoids, , myri- parently is present in both the heartwood and cetin, and probably quercetin. An additional fla- the sapwood, but surprisingly gallocatechin vonoid found in this bark is (querce- was absent. The most interesting components tin 3-O-rhamnoside), which was extracted at in addition to the tannins are the coumarin, one time for use as a yellow dye for and scopoletin (fig. 13) and the lignans, syringare- hair. Quercitrin is also present in willow oak sinol (see Magnoliacea), lyoniresinol, and lyon- bark. These flavonoids apparently are common iside (fig. 14). 2,6-Dimethoxybenzoquinone is minor constituents of oak bark and wood. The probably formed by free radical oxidation of European drug Cortex Quercus is the astrin- syringyllignans. Neither nor their gly- gent extract of oak inner bark. Oak bark also cosides could be detected. However, color contains inositols such as quercitol, first found tests suggested that several esters of hydroxy- in cork oak. Quercitol is also present in bear, cinnamic, vanillic, and syringic acids were bur, pin, and willow oak barks (285). The inhib- present as well as , arabinosides, itory substances in oak bark used for growing and xylosides. The inner bark was very different orchids have been identified as gallic acid and from either the sapwood or the heartwood. Al- tannins (107). though no gallic or ellagic acids were present, Northern red oak has been the most thor- tannin esters, catechin, flavonoids, and lyoni- oughly investigated of the eastern oaks. The re- side were tentatively identified. The general lationship between heartwood formation and chemistry of this bark has been studied (55), as phenolic extractives has been examined (235). has that of chestnut oak (34). Tartaric acid has been suggested as the cause of toxicity of red, black, northern pin, and bur oak heartwood ex- tracts against oak wilt fungus (32). A few cases of sensitivity to oak wood dust have been re- ported (386) but the allergen is unknown. Northern red oak is a valuable commercial wood, but its value is often degraded by a vari- ety of stains, most of which are due to the phe- nolics in the wood. Thus, contact of the wet wood with sources of iron such as concrete, steel wool, and other abrasives can lead to for- mation of blue-black iron (364). For- tunately, these are usually readily bleached with . Other stains develop from air oxidation of the phenolics in the wet wood, per- Figure 11 .–Oak triterpenes. haps with the help of enzymes. These stains often can be prevented by high-temperature

M 146 171 steaming. Extraordinarily high concentrations

-17- -18- -18- Spot No.1 Compound Isolated from heartwood, H, and sapwood, S 1 Ellagic acid H and S 20 Hamamelitannin H and S 40 Gallic acid H and S 42 Sinapaldehyde H and S 43 Coniferaldehyde H and S 50 Catechin S 75 Scopoletin H 76 Syringaldehyde H and S 77 Propioguaiacone (propiovanillone) H 78 Vanillin H and S 80 Lyoniside H and S 90 rac-Lyoniresinol H * 2,6-Dimethoxybenzoquinone H * Resorcinol H * H and S * p-Hydroxybenzaldehyde S 1*, Location on chromatograms unknown; probably masked under other spots. Figure 12.–Two-dimensional paper chromatography of acetone-water extractives of . Top, sapwood (S); bottom, heartwood (H) M 146 192

of heartwood can cause other stains lier in the wood (36). Coniferaldehyde and sin- around defects and injuries in the wood. Still apaldehyde have also been reported in post other stains result from microbiological attack Oak wood; these simple phenolics are probably or fall into the category of “mineral stains.” very common (36). The corresponding ferulic A full understanding of the phenomena of and sinapic acids and salicylic and gentisic stain development in oak wood will be attain- acids as well as pyrogallol, p-hydroxybenzal- able only when information on the chemistry of dehyde, eugenol, and D-mannitol have been re- oak heartwood extractives has progressed ported in various foreign oaks. Many of the typ- considerably. However, catechin and galloca- ical bark components have also been reported techin moieties are undoubtedly involved be- in the wood. cause they are relatively easily oxidized to White oak is also a general commercial deeply colored quinones. The quinones can be name for a group of oaks that include Quercus bleached by reducing agents to the less col- alba, Q. bicolor, Q. lyrata, Q. macrocarpa, Q. ored hydroquinones or oxidatively bleached by michauxii, Q. muehlenbergii, Q. prinus, Q. stel- cleavage of the quinoid ring. Because these lata, and Q. virginiana. In general the vessels of bleaching agents are not completely success- these oaks are plugged with tyloses making the ful in decolorizing stained oak wood, other fac- wood difficult to treat with preservatives. How- tors must be involved such as different chemi- ever, the tyloses also make white oaks water- cal chromophores or quinoid groups protected tight, thus ideal for liquor and wine barrels. Eu- as insoluble complexes. genol and two Quercus lactones (diastereoiso- The general chemistry of white oak bark mers of 3-methyl-4-octanolide) have been has been investigated (55). The heartwood was found in an unidentified member of this white found to contain scopoletin (14); gallic and el- oak group (217). The lactones were also found lagic acids; gallotannins and ellagitannins; si- in aged whiskey and are responsible for the tosterol; stigmasterol; campesterol; stigmas- woody odor of whiskey. Vanillin, syringalde- tanol; lignoceryl ferulate and related esters; tri- hyde, and related phenolics derived from lignin glycerides of linoleic, oleic and palmitic acids; also are important in the desirable odor contrib- and coniferaldehyde (57). Vanillin, syringalde- uted by oak barrels to whiskey and wine (324). hyde, and sinapaldehyde had been found ear- Old (extractive-rich) oak bonds relatively poorly

-19- Figure 13.–Some natural coumarins. Figure 14.–Oak lignans.

M 146 170 M 146 169 with phenol-formaldehyde . Water, or tives (297). even more efficient, sodium carbonate extrac- Although relatively little information has tion, has removed interfering materials. Since been published on eastern oaks, if what is the addition of extra sodium hydroxide im- known is combined with extensive studies on proves bonding, the deleterious effect may be foreign oaks, a pattern does indeed emerge. predominately caused by acidity of the extrac-

HAMAMELIDACEAE

Liquidambar styraciflua L., sweetgum stored in normal wood or bark. Apparently sto- Sweetgum is the most common hardwood rax is formed in traumatic ducts near a species in the Southeast. The comparative wound. The most recent references (72,329) phenology, , and of and a number of articles in the popular press populations of this species have been investi- have contained little scientific data. Surpris- gated (377). Sweetgum is the source of an ex- ingly, no work has been reported on the chem- udate known locally as sweet gum and com- istry of American storax since 1921, when even mercially as American storax (styrax); it sells for earlier work reporting the presence of cinnamyl just under $1.50 per pound. Although current cinnamate and related esters was confirmed production is small ($150,000/yr, Clark Co., (125). American storax is a true balsam. The Ala.), this was a significant industry during and natural products chemistry of this material after World War I (117,211). American storax, might be worthy of further study. Oriental sto- essentially identical to Oriental storax from Li- rax has been found to contain oleanolic, 3-epi- quidambar orientalis in Turkey, has been used oleanolic (first time in nature), and oleanonic in perfumery, , incense, , acids (163). adhesives, pharmaceutical preparations as Sweetgum heartwood is difficult to glue, well as in folk medicine (187). has intermediate decay resistance, and is rela- Storax is obtained by collecting the exu- tively impermeable. Although in the early part of date from cuts made through the bark. Yields this century an ether extract of the heartwood are up to 1 pound per tree per year, most of was reported to cause dermatitis (307,386), this which is collected during the mid-June to mid- does not seem to be a problem with this spe- October growing period. Very little storax is cies. The quantities of extractives in the wood

-20- apparently are highly variable (167,368). The spectively. In contrast to the wood with very lit- ether extractives of the wood contained the tle tannin, the bark has been reported to con- usual fatty acids and esters as well as β-sitos- tain 7.6 percent tannin. Hot-water extracts of terol (368). the bark produce large amounts of precipitate Sweetgum sapwood has been extensively with gelatin or with formaldehyde-hydrochloric studied and found to contain a large amount of acid (55). Hegnauer reported Plouvier (143) vanillic and syringic acids plus 3,4-dihydroxy- found that the bark contains 0.1 percent shi- phenyl, galloyl, and related hydrolyzable tan- kimic acid, and that both the wood and bark nins. Lesser components included vanillin, syr- contain the iridioside, monotro- ingaldehyde, coniferaldehyde, sinapaldehyde, pein (fig. 9) (215). The phenolics in the bark ap- m-coumaraldehyde, gallic acid, dihydroquer- parently are closely related to those in the sap- cetin, glucose, fructose, and soluble lignin wood and include large amounts of gallic and fragments (180,332). Ellagic acid plus related ellagic acids plus 3,3´-di-O-methylellagic acid, methyl ethers and glycosides are also indicated other methylated ellagic acids, related glyco- (332). Polymeric phenolic glycosides predomi- sides, and ellagitannins and gallotannins (332). nate and apparently in the heartwood are heav- Although there are many similarities between ily polymerized and oxidized to colored nontan- the bark and the sapwood extractives, distri- nin polymers. The heartwood has recently been butions of the individual components are shown to contain quercetin (332). different. The general chemistry of the bark has been The tannin-rich leaves of the sweetgum studied (55). Successive extractions with ben- tree are still used today as a folk remedy to re- zene, 95 percent ethanol, hot water, and 1 per- lieve sore throat and diarrhea. The dry, spiny cent sodium hydroxide dissolved 1.5 percent, mature fruit is burned, and the ash applied to 17.7 percent, 7.4 percent, and 21.3 percent, re- sores and burns (226).

HIPPOCASTANACEAE

Aesculus glabra Willd., buckeye A. octandra Marsh., yellow buckeye A. parviflora Walt., bottlebrush buckeye A. pavia L., red buckeye A. sylvatica Bartr., painted buckeye Almost nothing is known about the extrac- tives of eastern buckeyes. The wood is of lim- ited commercial significance, has essentially no color, odor, or , and is of low durability. These facts suggest that study of the extrac- tives of the wood and the bark of this genus would not be particularly rewarding, although the barks of some other Aesculus species have had limited pharmaceutical use. Yellow and red buckeye woods have been reported to contain no tannin, although yellow buckeye bark con- tains 28 percent and red buckeye bark, an in- significant amount (304). The general chemistry of the Hippocastan- aceae has been summarized (143). Most re- Figure 15.–Proanthocyanidin ports on this genus deal with the European (-)-epicatechin-A2. M 146 168 chestnut, Aesculus hippocastanum, the chemistry of which has been reviewed (154).

-21- Aescin, the triterpene saponin of the barks of Aesculus species. horse chestnut seeds, also occurs in the bark. Horse chestnut husks, and to a lesser ex- Therefore, triterpene saponins may also be tent the bark, contain simple flavonoids and present in eastern U.S. buckeye barks, al- condensed tannins. The structures of several though no more than traces were detected in dimeric and trimeric condensed tannins [e.g., bottlebrush buckeye bark. Coumarins are proanthocyanidin (-)-epicatechin-A2 (fig. 15)] found in the wood, and especially in the bark of have been elucidated (168). this genus. They account for the fluorescence Twigs of red buckeye contain traces of of the aqueous bark extracts, although bottle- quebrachitol that apparently is widespread in brush buckeye bark lacks this fluorescence. this genus. Allantoin and allantoic acid appar- Yellow buckeye bark contains a polar coumarin ently are common sap constituents analogous of unknown structure (109). All of the coumar- to the Aceraceae, which has many chemical ins esculetin, esculin, scopoletin, , similarities to this family. fraxetin, and fraxin (fig. 13) have been found in

JUGLANDACEAE

Carya aquatica (Michx. f.) Nutt., water hickory Shagbark 0 4.7, 6.7 C. cordiformis (Wangenh.) K. Koch, bitternut Shell bark hickory 5.7 C. floridana Sarg., scrub hickory All woods were reported as not containing tan- C. glabra (Mill.) Sweet, pignut hickory nin, although young whole pecan plants con- C. illinoensis (Wangenh.) K. Koch, pecan tain 11.5 percent tannin (127). It is intriguing C. laciniosa (Michx. f.) Loud., shellbark that in a survey of the general chemistry of pe- hickory can bark, the benzene-extracted bark had an C. myristicaeformis (Michx. f.) Nutt., extraordinarily large amount of ethanol extract, hickory 18.1 percent (55). Pecan bark contains azalea- C. ovata (Mill.) K. Koch, shagbark hickory tin (quercetin 5-methyl ether); the new flavonol, C. pallida (Ashe) Engl. and Graebn., sand caryatin (quercetin 3,5-dimethyl ether) (308) hickory and juglone. C. texana Buckl., black hickory The occurrence of juglone apparently is C. tomentosa Nutt., mockernut hickory characteristic of the barks (especially the Juglans cinerea L., butternut husks) of this family, and probably explains J. microcarpa Berlandier, little both the use of pecan bark by Mexican Indians J. nigra L., black walnut to stupefy fish (260) and of the hickory bark to Extractives of Carya species have had little repell (see Ulmaceae). Juglone is also a investigation. The chemistry of this family has purgative (butternut and black walnut bark been reviewed (103,143); there is an early re- have been used to make a (187)). Jug- port on the chemistry of hickory inclusive of pe- lone can cause blackening, blistering, and can (223). An extensive review has been made peeling of the skin; is a tranquilizer and seda- of the chemistry and the biochemistry of walnut tive (28,374); has antitumor activity (29); is fun- trees (81). gitoxic and an antibiotic; and is allelopathic Tannin content of hickory and pecan barks (330). Unquestionably, this is a significant are given in the following tabulation (304). compound. Species Percent Juglone or a precursor is probably the ac- Hickory: tive substance responsible for dermatitis from Bitternut 7.8 the nutshells, , and bark of black walnut. Mockernut Insignificant, 5.0-9.8 Juglone has not been reported in the wood and Pignut 7.6-10.0 no cases of skin or mucosal irritation by the Sand 6.7 wood have been found (386). Juglone is formed

-22- in a tree from dihydrojuglone-4-glucoside via the durability of the heartwood have not yet dihydrojuglone (fig. 16) and readily polymerizes been identified. The bark components appar- to brown-black pigments. Apparently it is part ently are absent from the wood. Ellagic acid is of the wound response mechanism, although it a sedative and tranquilizer (28) and has antitu- is not reported in the wood. mor activity (29). In one case a dog chewed on Black walnut is the most valuable eastern a black walnut statue and fell into a deep sleep, hardwood, is highly decay resistant, and is much to the distress of the owner. After 48 prized for its dark color. The influence of light hours, the dog awoke with no apparent ill ef- on the color of the wood has been studied fects. Both black walnut and butternut woods (220). The American Indians used the roots as contain coniferaldehyde and sinapaldehyde a source of a black dye and the leaves, husks, (36). and nuts as the source of a brown dye. The Butternut wood also contains large heartwood contains only about 10 percent total amounts of gallic acid, ellagic acid, and two extractives (70), the function of which has been -like compounds (316). However, discussed (235). The bark has been found to the wood is reported to contain only insignifi- contain the flavonoids , myricitrin cant amounts of tannin; the bark contains 7.9 (myricetin-3-rhamnoside), sakuranetin and percent (304). The heartwood is nondurable, sakurenin (sakuranetin-5-glucoside); the chal- without odor or taste, and darkens on exposure cone glucoside neosakuranin; and juglone and to light. It is rich in gallic acid and also contains dihydrojuglone-4-glucoside (126). Neither the ellagic acid, proanthocyanidins, and gallotan- wood nor the bark contains tannins. However, nin-like compounds. β -Sitosterol and gallic the wood contains appreciable amounts of gal- acid were found in butternut bark (316). A pat- lic acid as well as ellagic acid, glucose, and a ent has been issued for an antibiotic isolated dark violet polymer (126,316). The oxidation from the root bark for use as a food preserva- and the condensation of gallic acid and its de- tive (170). The American Indians used the rivatives into soluble polymers is a well-known husks for a brown dye. phenomenon. The compounds responsible for

Figure 16.–Formation of juglone.

M 146 167

LAURACEAE

Sassafras albidum (Nutt.) Nees, sassafras tains 8.5 percent tannin in the bark, but no tan- This family is most attractive chemotaxon- nin in the wood (304). A water-soluble omically because of the number of unusual ex- polysaccharide of the twigs is pharmaceutically tractives. These extractives are discussed in a active (333). Researchers of the Forest Service recent excellent review (122) as well as in ear- at the Southern Forest Experiment Station are lier reviews (103,143). The only eastern mem- investigating termiticidal components in ber of this family, sassafras, reportedly con- sassafras.

-23- The literature back to the early 19th cen- tury contains numerous references to sassa- frass, mostly because of the pharmaceutical use of the oil of the root bark that contains saf- role (80 pct of the oil) (fig. 17). The volatile con- stituents from the root bark oil also include α- pinene, , α - and β -phellandrene, I- menthone, thujone, anethole, copaene, cary- ophyllene, eugenol, 5-methoxyeugenol, elemi- cin, coniferaldehyde, myristicin, asaron, pipe- ronylacrolein, syringaldehyde, and apiol (318). The root bark contains the aporphine alkaloids boldine, norboldine, and isoboldine and the 1- benzyl-1,2,3,4-tetrahydroisoquinoline alkaloids norcinnamolaurine, cinnamolaurine, and reti- culine (63) (fig. 18). The methylene chloride ex- tract of sassafras root (wood) contained the lig- nans D- and desmethoxyashantin (fig. 19) as well as β -sitosterol, piperonylacrolein, and ( + )-safrolglycol (151). Sassafras oil, one of the oldest and best known American essential oils and one of New England’s first plant-derived exports, is ob- tained in 6 to 9 percent yield by steam distilla- tion. In colonial days, it was used for a tea, a su- dorific for colds and a spring tonic to “get the winter sluggishness out of the blood.” The tea has been used in folk medicine as a diaphor- etic, stimulant, diuretic, carminative, and to Figure 18.–Alkaloids from Sassafras albidum. treat bronchitis (187). The most important 20th- century uses of the oil have been in flavoring, M 146 174 especially sarsaparilla and root . Safrole was for many years the chief flavoring ingredi- ent in . If root beer no longer has the

Figure 17.–Safrole and related compounds from Sassafras albidum. Figure 19.–Lignans from Sassafras albidum.

M 146 173 M 146 175

-24- kick it had, it may be because the Food and The carcinogenicity of safrole is due to its Drug Administration in 1960 banned the use of metabolic conversion to 1´-hydroxysafrole, a safrole. The ban resulted from long-term, rat- proximate carcinogen (37,38). Further activa- feeding studies that showed safrole could tion for carcinogenesis and mutagenesis can cause liver cancer. In 1976 FDA banned sas- occur by either esterification of the 1´-hydroxy safras bark intended primarily as a vehicle for group or by epoxidation of the 2´,3´-double sassafras tea. However, safrole-free sassafras bond (379,380). bark (and leaf) extracts can still be used.

LEGUMINOSAE Gleditsia aquatica Marsh., waterlocust the major component (4-5 pct) found in the G. triacanthos L., honeylocust heartwood, and D-fustin; the flavonols robine- Robinia kelseyi Hutchins., Kelsey locust tin (3,3´,4´,5´,7-pentahydroxyflavone) and fise- R. pseudoacacia L., black locust tin; the flavan-3-ol L-robinetinidol (3,3´,4´,5´,7- R. viscosa Vent., clammy locust pentahydroxy-2,3 -trans-flavan); and the flavan- In recent literature (130,132), the chemistry 3,4-diols leucorobinetinidin and D-3,3´,4,4´,7- of the Leguminosae is discussed in detail. Hon- pentahydroxy-2,3- trans-3,4-cis-flavan. In addi- eylocust is the only eastern Gleditsia species tion the heartwood contained β-resorcylic acid investigated; this has involved mostly leaves and methyl β -resorcylate (188). and fruit. Indeed, this tree is named after the The compounds responsible for the lumi- sweet succulent pulp found in the pod. D- nescence and in part for the very high decay re- Fustin[(2 R,3R)-3,3´,4´,7-tetrahydroxyflavan- sistance of this wood are extractable with one] and (3,3´,4´,7-tetrahydroxyflavone) ethanol (209). Dihydrorobinetin inhibits growth are the major extractives in the heartwood of fungi, thus must contribute to the wood’s du- (54). Roy and Prudy, University of Toronto, rability (108). However, the fungicidal phyto- have told us that some 20 minor phenolics are alexins common in this family are considered to detectable by thin-layer chromatography in- be pterocarpans such as have been reported in cluding vanillin, triacontanyl ferulate and re- black locust (147). The flavonoids also have lated ester, and other flavonoids. been implicated for causing an eczema from Black locust is the only eastern true locust contact with this wood (386). Although disco- that has had wood and bark extractive content lored sapwood near wounds resembles heart- investigated. Although tannins have been re- wood, this wood differs chemically from heart- ported absent in both the wood and the bark of wood (135). Nucleic acids and their compo- honeylocust and black locust (304) black lo- nents are present in the sievetube sap (389) cust wood has been reported to contain 1.5 and the wood and the leaves contain the anti- percent tannin and the bark, 1.6 percent (169). biotic, trans-2-hexen-1-al. These are apparently condensed tannins (poly- Black locust bark has been the subject of leucorobinetinidins) similar to those in wattle numerous studies. Early work has shown the (130,300). The flavonoids have been thor- presence of stigmasterol, , syringenin, oughly investigated (188,300,301). Essentially starch, and simple sugars, and related metab- the same flavonoids were detected in the heart- olites. However, most interest has centered on wood and the sapwood, but the heartwood the high- content of the bark. In 1890 a contained considerably larger quantities. The phytohaemagglutin, robin, was isolated from flavonoids found include the robtein the bark (132). The bark contains up to 4.5 per- (2´,3,4,4´,5pentahydroxychalcone), cent of water-soluble protein that can be read- (2´,3,4,4´-tetrahydroxychalcone), and 2´,4,4´- ily isolated due to the low amount of tannin in trihydroxychalcone; the L-robtin the bark. These proteins vary seasonally and [(2S)-3´,4´,5´,7-tetrahydroxyflavanone], L-butin are implicated in frost hardiness (100,323). The [(2S)-3´,4´,7-trihydroxyflavanone] and liquiriti- bark phospholipids also vary seasonally; phos- genin [(2S)-4´,7-dihydroxyflavanone]; the fla- pholipids have been detected in the wood by vanonols D-dihydrorobinetin [(2R, 3R)- staining (73). 3,3´,4´,5´,7-pentahydroxyflavanone], which is

-25- MAGNOLIACEAE

Liriodendron tulipifera L., yellow-poplar Other alkaloids in the heartwood and the dis- Magnolia acuminata L., cucumbertree colored sapwood included dehydroglaucine, M. ashei Weatherby, Ashe magnolia norglaucine, liriodenine [identical with sper- M. fraseri Walt., Fraser magnolia matheridine, oxoushinsunsine, and micheline M. grandiflora L., southern magnolia B (344)], O-methylatheroline (oxoglaucine), nu- M. macrophyla Michx., bigleaf magnolia ciferine, nornuciferine, N-acetylnornuciferine, M. pyramidata Bartr., pyramid magnolia norushinsunsine, asimilobine, and N-acetylasi- M. virginiana L., sweetbay milobine. At least two unidentified 1-benzylte- The chemistry of the Magnoliaceae has trahydroisoquinoline type alkaloids were found been reviewed (103,143). The pale color of yel- in the heartwood. Except for the oxoaporphine low-poplar heartwood, the low durability, the pigments liriodendronine and corunnine, the low extractives content, and the fact that yel- compounds isolated from the discolored heart- low-poplar containers do not impart taste or wood were similar to those found in the normal odor to foodstuffs suggest the extractives may heartwood. In contrast the discolored sapwood not be of interest. This is not true. contained not only liriodendronine, corunnine, Yellow-poplar is the most toxic of all of the and the compounds mentioned, but in addition, woods reviewed in this paper; it causes severe thaliporphine, predicentrine, N-methyllaurote- dermatitis on contact with either the green or tanine, lirioferine, and liriotulipiferine that were the wet wood, and is even more severe, after not detected in either normal heartwood or dis- contact with the bark (314,386). Fresh bark colored heartwood infested by micro-orga- should probably not be used as a or a nisms. Thus the formation of these phenolic conditioner because the bark appreciably aporphines in the discolored sapwood proba- retards the growth of garden pea seedlings (11) bly did not result from microbial metabolism of and is toxic to seed according to , although the microbial N- and O-de- E. G. Scott, West Virginia University, alkylation of glaucine has been reported (74). Morgantown. Production of aporphine alkaloids is stim- The extractives from wood, bark, and ulated by injury-apparently to inhibit the leaves of yellow-poplar have been investigated. growth of invading micro-organisms. Thus They include alkaloids (fig. 20A, B), sesquiter- glaucine, N-methyllaurotetanine, lirioferine, penes (fig. 21), and lignans (fig. 22). No signifi- and liriotulipiferine have been found to have cant tannin was found in either bark or wood antimicrobial activity against fungi but not bac- (304). teria inhabiting the wood of yellow-poplar Yellow-poplar is a rich source of aporphine (158). In addition, dehydroglaucine and lirio- alkaloids. The wood, bark, cortex, leaves, and denine, a known cytotoxin (371), have been seeds contain alkaloids (357,358,395). The al- identified as antimicrobial agents (61,162). kaloids in the bark probably explain why bark Liriodenine and O-methylatheroline, which extracts were used medicinally for treating ma- can be formed by auto-oxidation of glaucine, laria during the War of Independence. The al- are responsible for the yellowish-green color of kaloid glaucine is used as an antitussive in the normal heartwood of yellow-poplar (43,60,68). Soviet Union. Recent investigations have Liriodendronine and corunnine are responsible shown that the heartwood fraction has in part for the discoloration of injured wood antimicrobial activity (162). (62,315), which ranges from yellow-green to An extensive investigation of the alkaloids pink, red, purple, blue, brown, and even black. in yellow-poplar wood was conducted by Chen In addition, other investigations showed the and others (58,60,62,315), who studied sap- presence of N-acetylnornantenine (161), 3- wood, discolored sapwood formed after injury, methoxy-N-acetylnornantenine (161), ushin- heartwood, and discolored heartwood infested sunsine (michelabine) (162), N-acetylanonaine by micro-organisms. Glaucine, the only alkaloid (160), and tuliferoline (160). detected in sapwood, was the major alkaloid in Extensive Russian investigations recently the heartwood and the discolored sapwood. have been on the alkaloids in yellow-poplar

-26- Figure 20.–Yellow-poplar alkaloids. M 146 177 M 146 176 Figure 22.–Yellow-poplar lignans.

M 146 179 Figure 21 .–Yellow-popular sesquiterpenes.

M 146 178 leaves with limited work on the wood and the greater for mixtures of these compounds than bark (1,2,390-395). The compounds that were for the individual compounds. In addition to the isolated included liridine, caaverine, lirinidine noraporphine alkaloids and sesquiterpene lac- (N-methylcaaverine), lirinine, lirinine O-methyl tones, yellow-poplar bark extracts also contain ether, lirinine N-oxide, isolaureline, lysicamine, large amounts of simple sugars, some pheno- isoroemerine, nornuciferine, langinosine, liri- lics and coloring materials, a pleasant smelling dinine, and N-methylcrotsparine. , esculetin dimethyl ether (fig. 13) Lirinine and lirinine O-methyl ether were (358) liriodendritol (mesoinositol-1,4-dimethyl identified as 1-hydroxy-2, 9-dimethoxyapor- ether) and methyl syringate (58). The amount of phine and 1,2,9-trimethoxyaporphine, respec- total alkaloids in the extract is insignificant al- tively, by Yunusov and others on the basis of though trace amounts of norlirinine O-methyl spectroscopic analysis (392). However, the nu- ether, nornuciferine, and N-(2-hydroxy-2-phen- clear magnetic resonance (NMR) spectrum of ylethyl) benzamide were isolated from this frac- lirinine is incompatible with the proposed struc- tion (58). The lignans (+)-pinoresinol (fig. 2) ture (58). Of the two methoxyl resonances, the ( + )-syringaresinol, the coniferyl-sinapyl ana- one at higher field (τ 6.37) corresponded to a log ( + )-medioresinol, and their monogluco- C-1 methoxyl resonance (30). The aromatic re- sides and diglucosides e.g., liriodendrin, as gion of the spectrum integrated for four hydro- well as the unusual lirionol were also gens that constituted an ABCX spin-system found in the bark (58,82,111). corresponding to four adjacent aromatic hy- Liriodendrin is a derivative of ( + )-syrin- drogens. An H-3 resonance around τ 3.50 was garesinol (lirioresinol B) (40,216). Dickey’s “lir- absent. In addition, the spectrum was almost ioresinol C” was shown to be impure lirioresi- identical to that of liridinine (2). Therefore, nol B (40). ( + )-Syringaresinol, syringaresinol lirinine and liridinine should be isomers, i.e., 3- dimethl ether, and the simple phenol, syringal- hydroxy-1,2-dimethoxyaporphine and 2-hy- dehyde, were found in yellow-poplar heart- droxy-1,3-dimethoxyaporphine, respectively, wood (60,62,162). In studies on the biogenesis or vice versa. Lirinine O-methyl ether should of the lignans in the bark (110), sinapyl alcohol then be 1,2,3-trimethoxyaporphine. Although was found, as expected, the best precursor. the structure 2-hydroxy-1,3-dimethoxyapor- However, the free syringaresinol and the lirio- phine was assigned to liridinine by the Russian dendrin were, surprisingly, the (-) form in con- authors on the basis of the NMR spectrum, C- trast to the ( + )-isomers normally found. Ap- L. Chen, University, Raleigh, parently a tree can synthesize both antipodes. believes that further research is required to es- In addition to free syringaresinol and its mono- tablish the structures of lirinine and liridinine. glucoside, also found were the coniferyl ana- The isolation of the proaporphine alkaloid log, ( + )-pinoresinol, and ( + )-medioresinol. N-methylcrotsparine and the benzyltetrahy- Yellow-poplar contains a most unusual se- droisoquinoline alkaloids mentioned are inter- ries of extractives including compounds of un- esting because compounds of this type are usual structures as well as an extraordinary ar- postulated as intermediates in the ray of alkaloids, a class of extractives seldom of aporphine alkaloids from and found in temperate zone trees. The largest (17,122). group of these are the aporphine alkaloids. The yellow-poplar bark (root) extractives They occur in two series depending on the ster- contain a series of sesquiterpene lactones: eochemistry at 6a. The compounds with a hy- Costunolide, tulipinolide, epitulipinolide, epitu- drogen at this position extending above the lipdienolide, and γ-liriodenolide (83,84,87, plane of the ring (S-absolute ) 88,92). The related compounds lipiferolide, ep- are generally dextrorotatory [( + )]. Those with itulipinolide diepoxide, and peroxyferolide (the a hydrogen extending below the plane of the first naturally occurring germacranolide hydro- ring (R-absolute stereochemistry) are generally peroxide) have been observed in the leaves levorotatory [(-)]. (90,91). Most of these compounds are cytotoxic The extractives of magnolia wood and bark and inhibit feeding by gypsy moth larvae are also characterized by lignans (fig. 23) and (Porthetria dispar L.) (92). Interestingly, Dos- alkaloids, but are of a wider variety than are kotch finds that the antifeeding activity is those of yellow-poplar. Thus, the alkaloids also

-29- Figure 23.–Lignans of magnolias.

M 146 180

include phenylethylamine, benzylisoquinoline, Alkaloids have been studied only in the and bisbenzylisoquinoline types. Most of the cucumbertree and southern magnolia (143). recent work on magnolias has been in Japan by The cucumbertree contains salicifoline and groups such as Fujita’s (112-115). The essen- candicine in the roots and salicifoline and tial oil of the bark (especially on branches) of magnoflorine in the bark, whereas the mag- eastern magnolias should perhaps be studied. nolia contains choline, magnoflorine, salicifo- The essential medicinal oils from Japa- line, magnocurarine, and D-O-methylarmepa- nese magnolia barks consist of a mixture of in the stem. More recently, the alkaloids monoterpenes and sesquiterpenes with a very of southern magnolia wood have been found high content of β -eudesmol in one species to include anolobine, anonaine, N-nornucifer- (113) and a high content of trans-anethole in ine, liridenine (359) and candicine (296). Many another (112). Syringin is a common constitu- literature references in which magnoflorine ent of bark of Magnolia species. Lignans are has been identified may be in error because of also common in barks. Sweetbay contains a the similarity in its properties to those of N,N- small amount of magnolol (115), whereas the dimethyllindcarpine (339, footnote 5). The bark (especially root bark) of the cucumber- bark of southern magnolia has recently been tree, used at one time as a drug in the treat- shown to contain the glycosides magnolidin, ment of malaria and rheumatism, contained magnolenin, and magnosidin (296). the lignans calopiptin, galgravin, veraguensin, Extracts of a cross between southern mag- and acuminatin (85). nolia and sweetbay have yielded an extract in-

-30- hibitory against both fungi and bacteria (326). should be checked for physiological activity. A corn whiskey extract of bigleaf magnolia in- Biologically active (cytotoxic) sesquiterpenes ner bark has been used in northeastern Ala- related to peroxyferolide have been obtained bama as a diuretic and to treat arthritis. from southern magnolia (96). Neither the wood Although corn whiskey alone would help re- nor the bark of southern magnolia or sweetbay lieve suffering, the alkaloids of the inner bark contains significant tannin (304).

MORACEAE

Maclura pomifera (Raf.) Schneid., Osage- the first natural product shown to contain the orange 1,1-dimethylallyl form of isoprenoid substitu- Morus rubra L., red mulberry tion. Macluroxanthone has antitermiticidal ac- M. alba L., white mulberry tivity, whereas osajaxanthone and alvaxan- The extractives, particularly the phenolics, thone are toxic to goldfish and mosquito of the Moraceae have been reviewed (362). The larvae. flavonoids (fig. 24) and the stilbenes, which are The heartwood of Osage-orange has al- the major types of compounds isolated from so been reported to contain resorcinol, this family, may be useful chemotaxonomic kaempferol, dihydrokaempferol, dihydro- markers. The wood and the bark of Morus spe- kaempferol-7-glucoside, quercetin, dihydro- cies and the bark of Osage-orange do not con- quercetin, and dihydromorin (78,93,194). It tain significant tannin. The wood of Osage-or- has been suggested (194) that since morin is ange contains 9.4 percent tannin (304). produced by autoxidation of dihydromorin Osage-orange is a small, rapid-growing tree; the wood is very dense, has high strength properties, and is resistant to decay. The gen- eral morphological and chemical difference be- tween sapwood, discolored sapwood, and heartwood of Osage-orange has been studied (135). The mucilaginous sap of the wood causes dermatitis (386). During World War I when imports of dyes were curtailed, Osage-orange wood was used as a dyestuff. After the War, Osage-orange be- came of minor importance as a dyewood be- cause of the availability of imports and other sources of dyestuffs. Early studies indicated that the dyestuffs from the wood were morin (2´,4´,5,7-tetrahydroxyflavonol) and maclurin (2,3´,4,4´,6-pentahydroxybenzophenone) (186). Subsequent work (16,381) indicated that the heartwood contained the pigments morin, oxy- (2,3´,4,5´-tetrahydroxystilbene), and 1,3,6,7-tetrahydroxyxanthone, but the presence of maclurin was not confirmed (16). Oxyresveratrol is apparently the fungicidal (16) and termiticidal agent in Osage-orange wood responsible for its resistance to decay. The root bark contains the pigments ma- Figure 24.–Flavanoids from Moraceae. cluroxanthone, osajaxanthone, and alvaxan- thone (382-385) (fig. 25). Macluroxanthone is M 146 181

-31- Figure 25.–Xanthones from Osage-orange (Maclura pomifera).

M 148 184 -32- (51) some of the morin reported from the Mor- rence of rubranol in the bark of both species. aceae may be an artifact produced during ex- Rubranol and albanol are formed, at least con- traction and subsequent processing. However, ceptually, by dimerization of flavonoid inter- Venkataraman, who has conducted much of mediates. The rubraflavones are the first nat- the recent research on the extractives of the urally occurring with a geranyl sub- Moraceae, believes that this “certainly does stituent and rubraflavone A is the first flavone not apply to [his] results,” and morin is defi- containing an alkenyl substituent in only the C- nitely present (362). Similarly quercetin and ring. The root bark of white mulberry has been kaempferol can be formed by autoxidation of dihydroquercetin and dihydrokaempferol, re- spectively. Researchers should take sufficient Table 2.–Heartwood extractives of Morus alba and care to avoid autoxidation if isolating M. rubra1 dihydroflavonols. Compound M. alba M. rubra The bark of Osage-orange contains 8-des- Simple phenolics oxygartanin, 6-desoxyjacareubin, osajaxan- Resorcinol + + thone, and toxyloxanthones A, B, C, and D β -Resorcylaldehyde ++ (78). The structure of toxyloxanthone B, the Protocatechualdehyde + first naturally occurring 4,4-dimethylchro- Benzophenones Maclurin + mene, has recently been revised (71). 2,4,4´,6-Tetrahydroxy- The roots of Osage-orange contain lu- benzophenone + peol, butyrospermol, β -sitosterol, and lupane- Stilbenes 3β, 20-diol (94). Similar triterpenes have been Resveratrol + ++ found in the fruit of female trees. Oxyresveratrol Dihydrooxyresveratrol + Morus species are small trees valued for 3,3´,4,5´-Tetrahydroxy- their foliage as silkworm food, edible fruits, stilbene (“piceatannol”) + and for use as dyestuffs. The heartwood ex- Flavonoids tractives of white mulberry and red mulberry Kaempferol + ++ have been reported to contain various simple Dihydrokaempferol Norartocarpanone ++ phenolics, benzophenones, stilbenes, and fla- Morin ++ vonoids (Table 2,3; fig. 26). However the pres- Dihydromorin + + ence of benzophenones has not been con- Quercetin ++ firmed (194). Alboctalol apparently is formed in Dihydroquercetin + vivo by a complex multistep dimerization proc- () Other ess from oxyresveratrol or, alternately, alboc- Alboctalol + talol and oxyrsveratrol have a common bioge- 1 +, Detected; -, not reported; data from literature cited netic precursor (363). The original structure of 76,77,184,194,331,362,363. alboctalol (77) has been revised recently (363). The heartwood of white mulberry also con- tains the sugars glucose, , xylose, and mannose plus two unknown oligosaccha- Table 3.–Flavonoids in the bark of Morus alba and M. rubra 1 rides (164). The seasonal variation of the sug- ars in the bark and the twigs of M. alba in re- Compound M. alba M. rubra lationship to frost hardness has been studied Mulberrin + (306). Mulberrochromene + α β Cyclomulberrin + Bark of white mulberry contains - and - Cyclomulberrochromene + , betulinic acid, palmitic and stearic Mulberranol + acids, and various sugars (75,362). β-Sitos- Albanol + terol was also present in the bark, and was the Rubranol + + - sole compound identified in callus tissue Rubraflavone A + Rubraflavone B + (189). In addition the barks of both white and Rubraflavone C + red mulberry contain a variety of flavonoids Rubraflavone D + (table 3). The flavonoid components in these 1 +, Detected; -, not reported; data from literature barks differ markedly except for the occur- cited 75,77,79,363.

-33- shown to contain β -tocopherol; α,β -dimontan- mulberrochromene); and another compound ylglycerol; morusin (an isomer of mulberro- also related to cyclomulberrochromene chromene); cyclomorusin (an isomer of cyclo- (182,239,319).

Figure 26.–Compounds from Morus species. M 146 185 M 146 191

-34- -35- NYSSACEAE

Nyssa aquatica L., water tupelo extract contained glucose, rhamnose, lactose, N. ogeche Bartr., Ogeechee tupelo and phenolic glycosides (363). chro- N. sylvatica Marsh., black tupelo matography of the benzene and of an ethyl Tupelo wood is used principally for lum- acetate extract resulted in three crystalline ber, veneer, , and railroad ties. The low-yield phenolics, the structures of which porous wood of Nyssa species has been used have not been determined (363). in certain surgical procedures (224). Tupelo Preliminary work on the extractives of wood lacks durability if conditions promote de- black tupelo heartwood indicates the pres- cay; the heartwood, however, is easily pene- ence of an alkaloid in minute amounts, phe- trated by preservatives. nolics, and one or more flavones (363). The Although the general chemistry of black ether extract of the prehydrolysis pulping liq- and water tupelo woods (368) and of black tu- uors of black tupelo contained vanillic acid, pelo bark (55) have been investigated, no de- , vanillin syringaldehyde, sinapal- tailed studies have been conducted on extrac- dehyde, and vanilloyl methyl ketone (334). The tives of this genus. Neither the wood nor the extractives of Nyssa species and indeed the bark has any significant tannin content. entire Nyssaceae have not been investigated Water tupelo heartwood contains 0.26 extensively. Because other members of this percent benzene extractives, 0.3 percent ace- family contain pharmaceutically active alka- tone extractives, and 1.6 percent ex- loids, future studies of these species may be tractives. The acetone and methanol extracts rewarding. gave positive tests for alkaloids. The methanol

OLEACEAE

Fraxinus americana L., white ash the bark (386). The bark of F. americana has F. berlandieriana A. DC., Berlandier ash been used in folk medicine in a tonic, as a di- F. caroliniana Mill., Carolina ash uretic, and to relieve fever (187). F. nigra Marsh., black ash Neither wood nor bark of ash contains any F. pennsylvanica Marsh., green ash significant amounts of tannin, although white F. profunda (Bush) Bush, pumpkin ash ash bark reportedly contains 4.5 to 4.8 percent F. quadrangulata Michx., blue ash tannin (304). Tannin and carbohydrate con- F. texensis (A. Gray) Sarg., Texas ash tents of white ash bark have been reported The white ash wood used commercially is (229). primarily the white and the green ash, although Stachyose and especially mannitol are blue ash is often included. Because commer- characteristic sugars found in Fraxinus species cial white ash is heavy, strong, hard, stiff, and (244,284). Indeed, manna of commerce is the has high resistance to shock, it is used for han- dried exudation from F. ornus, the European dles, oars, baseball bats, and other similar flowering ash tree, which contains about 90 uses. Black and pumpkin ash are lighter in percent mannitol (manna sugar). However, the weight and are used for furniture and shipping manna that fell on the Israelites is thought to be containers. Ash wood is only slightly resistant a lichen (Lecanora spp.) that in dry weather to decay-promoting conditions. curls into flakes or balls that can be borne long A Fraxinus species reportedly caused der- distances on the wind. matitis on a woodcutter’s wife who developed Coumarins (fig. 13), flavonoids, simple it from contact with her husband’s working phenolics, and their glycosides are generally clothes. However, the sensitivity was traced to characteristic extractives of Fraxinus species. the lichen Lecanora conizaeoides that grew on The coumarin derivatives are responsible for

-36- the blue to blue-green florescence of the water is unique; it alone contains coniferoside (284). extract of the bark. Glycosides have been im- In addition to fraxin, fraxetin, esculin, and es- plicated as the active antibiotic substances culetin were isolated from both the wood and found in barks of white, green, and black ash the bark of black ash (247). The novel chro- (173). menol pennsylvanol (fig. 27) has recently been Bark of Fraxinus species commonly con- isolated from the bark of green ash (363). The tains syringin and coumarin. The barks of data obtained on the purified compound are white, green, and black ash contain syringo- best explained if pennsylvanol exists as a mix- side and fraxin (283,284). The bark of blue ash ture of tautomers as shown (363).

Figure 27.–Pennsylvanol.

M 146 190

PLATANACEAE

Platanus occidentalis L., American sycamore percent tannin (304). The wood and the bark of American sycamore is used for , ve- the Platanaceae are rich in triterpenes. Indeed neer, railroad ties, and fenceposts. American American sycamore contains betulinic acid, sycamore causes woodcutter’s eczema, and betulinic , β -sitosterol, and a new tri- the down under the young leaves is an irritant terpene, platanic acid (3β -hydroxy-20-oxo-30- to throat and eyes (386). norlupan-28-oic acid) in the bark, and betulinic The general chemistry of the bark has been acid in the heartwood (353,387). Stearic and investigated (55). The wood does not contain docosanoic acids have also been found in the tannins, but the bark is reported to contain 1.9 bark (353,387).

RHIZOPHORACEAE

Rhizophora mangle L., mangrove America. It fringes shores and estuaries and is Mangrove is a principal part of the coastal of primary importance as a land retainer and vegetation throughout tropical and subtropical builder. One of the largest mangrove forests in -37- the world is found in the Everglades National These difficulties can be overcome partly by Park of Florida. Mangrove leaves have been blending with other tannins to reduce the as- studied as a supplement to feeds and as tringency and the content, and by eliminat- a source of pharmaceuticals. An excellent re- ing the color chemically (279,305). Mangrove view on the utilization of this species has been tannins (325) and tannins from related species published (225). The bark, roots, young , (282) show promise in the formulation of adhe- and leaves are a possible source of dyestuffs sives. Chemically, mangrove tannin is probably (225). The bark and the bark resin have been similar to that of the closely related species, used as a native remedy for leprosy, elephan- Rhizophora mucronata. D. G. Roux, University tiasis, asthma, diarrhea, dysentery, and to treat of the Orange-Free State, South Africa, told us lesions of various kinds. The bark has also been this tannin consists predominately of highly used as a substitute for to alleviate fe- condensed 4,8-linked leucocyanidin tannins ver (225). that readily yield cyanidin and traces of a fla- Mangrove is best known as a source of tan- van-3,4-diol precursor on reaction with mineral nin (7,279,294). The wood does not contain acid. tannin, but the bark yields 11 to 23 percent hot- Because the extractives of mangrove have water extract containing 37 to 56 percent tan- not been studied in any detail and because cer- nin. The tannin is primarily in the inner bark. tain compounds, e.g., sulfur-containing alka- Mangrove tannin has several undesirable fea- loids, have been reported from related species, tures: Causes cracky grain in leather due to its a study of the chemistry of this species might astringency; has a high salt content; and its in- prove highly informative. tense red color has little trade appeal (225).

ROSACEAE

Prunus alleghaniensis Porter, Allegheny plum ments and has been used as an antitussive P. americana Marsh., American plum (187,335). P. angustifolia Marsh., Chickasaw plum The American Indians used the inner bark P. caroliniana (Mill.) Ait., Carolina laurelcherry of P. virginiana as a source of a red dye. Be- P. hortulana Bailey, hortulan plum cause the wood and the bark of P. serotina and P. mexicana S. Wats., Mexican plum P. angustifolia inhibit seed germination in a va- P. munsoniana Wight and Hedr., wildgoose riety of plants (178) Prunus species wood and plum bark chips probably should not be used as a P. myrtifolia (L.) Urban, myrtle laurelcherry mulch on seedbeds. P. nigra Ait., Canada plum P. pensylvanica L. f., pin cherry P. serotina Ehrh., black cherry P. umbellata Ell., flatwoods plum P. virginiana L., common chokecherry The Rosaceae consists of approximately 4,000 species, so that the Prunus species re- viewed here represent only a small segment of the family. P. serotina is the only native species of commercial importance for lumber produc- tion. The fruits of this and other species have been collected for food. A folk remedy for dispelling chills is a whis- key drink in which the inner bark of Prunus ser- otina has been steeped until the bitter proper- Figure 28.–Cyanogenetic glycosides. ties are extracted (228). The inner bark is used commercially as a flavoring agent for medica- M 146 189

-38- The extractives of the Rosaceae have been of tannins that contained monomeric and poly- reviewed (143). The characteristic compounds meric leucocyanidin (3,3´,4,4´,5,7-hexahy- found in this family generally have included droxyflavanol) units (42). cyanogenetic glycosides (fig. 28) polyphenols, The heartwood of Prunus serotina con- and pentacyclic triterpenes. The chemotaxon- tained (+)-catechin, , and 3-hydrox- omic classification of Prunus by the flavonoids ynaringenin (281). In addition to , the found in the wood has been studied (136). bark contained scopoletin, benzoic acid, tri- The cyanogenetic glycoside prunasin is methylgallic acid, p-coumaric acid, and phyto- found in all tissues of Prunus species (143). sterols (289). The leaves of P. serotina con- , a compound closely related to pru- tained the pentacyclic triterpenes ursolic acid, nasin, is also found in some Prunus species, ursol aldehyde, and the new triterpene, 2α,3α- and is used in the preparation of laetrile. The dihydroxy-12-ursen-28-oic acid (31). cyanogenic glycosides, especially in the fruit Several Prunus species are known to pro- stones and foliage of the Rosaceae, can be of duce bark gums that give simple sugars on hy- dangerous levels and are responsible not only drolysis (292). This gum production is stimu- for the loss of livestock but also of human lives lated by wounding the tree, and is the typical (179). The toxicity of the glycoside is due to its wound response of these species. Hillis (149) rapid hydrolysis to free hydrogen after recently reported that treatment of Prunus spe- ingestion. Thus the bark of P. capuli was used cies with chloroethylphosphoric acid, which by the Mexicans as a fish poison (280). For liberates above pH 4, produced mas- safety the foliage and fruit pits of all Prunus sive amounts of carbohydrate gum exudate species should be treated as potentially dan- containing only small amounts of polyphenols. gerous (179). The amount of gum produced was many times The wood of Prunus species has been re- that produced as a typical wound response. ported to contain up to 4.5 percent tannin. The Fungal attack of Prunus species caused the ac- bark contains approximately 3 to 8 percent tan- cumulation of isoolivil (a lignan) and scopoletin nin (304). Tannin of P. serotina bark consisted in the sapwood (137,150).

SALICACEAE

Populus balsamifera L., balsam poplar The genus Salix contains about 300 spe- P. deltoides Bartr., eastern cottonwood cies (65); approximately 100 are found in North P. grandidentata Michx., bigtooth aspen America (206). The willows range from small P. heterophylla L., swamp cottonwood plants to large trees, and generally grow along P. tremuloides Michx., quaking aspen the banks of streams or on lake shores. The wil- Salix amygdaloides Anderss., peachleaf willow lows that grow to tree size are used in limited S. bebbiana Sarg., Bebb willow quantities for veneer, pulpwood, artificial limbs, S. caroliniana Michx., Coastal Plain willow boxes and various containers, and for furniture S. disco/or Mühl., pussy willow parts. S. exigua Nutt., coyote willow The most widely studied extractable con- S. floridana Chapm., Florida willow stituents in the genus Salix are the phenolic gly- S. interior Rowlee, sandbar willow cosides (349) (fig. 29). The phenolic glycoside S. lucida MühI., shining willow is of widespread occurrence in this ge- S. lutea Nutt., yellow willow nus and has been used medicinally as an anal- S. nigra Marsh., black willow gesic (335). This probably explains the use of S. S. pellita Anderss., nigra bark tea as a folk remedy in treating colds S. petiolaris J. E. Sm., meadow willow accompanied by fever (187,226). Salicin and its S. pyrifolia Anderss., balsam willow derivatives are responsible for the bitterness of S. rigida Mühl., Missouri River willow willow leaves; as a result high levels of these S. sericea Marsh., silky willow compounds correlate well with the resistance

-39- of willows to opossum attack (214). Other com- vey of Populus species with emphasis on P. tre- pounds reported include the leucoanthocyani- muloides has been compiled (293). An impor- dins and the anthocyanins in leaves and bark tant class of extractives in the bark and the (20,33,39). leaves of this genus are the phenolic glyco- Of the willows found in the eastern United sides (350,351). A gas-liquid chromatographic States, only the extractives of Salix nigra wood screening method for detecting phenolic gly- and S. petiolaris bark have been studied. The cosides has been described as a chemotaxo- general chemistry of S. nigra bark has been ex- nomic aid in the botanical classification of Pop- amined (55). The wood does not contain signif- ulus species (336,337). The extractives of the icant tannin, although the bark contains ap- bark and the leaves often contain antimicrobial activity (47,124,181,204,208,218,369). Tricho- proximately 5 percent (304). The acetone and carpin is important as a decay resistance factor the ethanol extract of S. petiolaris bark was shown to contain the glycosides salicin, picein, in poplar bark (208). The general chemistry of vimalin, salicyloylsalicin, salireposide, grandi- the bark of P. tremuloides and P. heterophylla dentatin, populin, tremulacin or tremuloidin (or has been studied (55). Although the wood of both), and salicyloylsalicin-2-O-benzoate, ( + )- Populus species does not contain tannins, the catechin, and β -sitosterol (338). bark has been reported to contain approxi- mately 2 percent tannin. Pearl and coworkers (273,275) extracted Wood of Populus tremuloides has been ex- Salix nigra wood with 75 percent n-propanol tensively investigated (269). Saponification and and identified p-hydroxybenzoic acid in the ex- fractionation of the neutrals from the benzene tractives. The extractives were hydrolyzed with extract gave linoleic acid, oleic acid and a ho- alkali and fractionated to yield p-hydroxyben- mologous series of wax acids from C12 to C28 in- zoic acid as the major component and smaller cluding the odd-numbered acids except C27 amounts of syringic acid, vanillic acid, ferulic (269). The major alcohols found were glycerol acid, syringaldehyde, vanillin, acetosyringone, and the C24, C26, and C27 wax alcohols. An im- and acetovanillone. Acid hydrolysis (272) of the pure β -sitosterol apparently was present as propanol extractives gave vanillic and syringic well as an unknown later shown to be acids as the major hydrolytic products with citrostadienol (44). Petroleum ether extraction lesser amounts of p-hydroxybenzoic acid, va- of heartwood of P. tremuloides followed by sa- nillin, and syringaldehyde. In addition, after hy- ponification confirmed the presence of the C16- drolysis, galactose, glucose, and mannose C28 wax acids (6). Acetone extraction of the were found in quantity, whereas before hydrol- heartwood also yielded sitosterol glucoside in ysis only glucose and mannose occurred, in the insoluble fraction. On saponification the small amounts. Thus, apparently the acids and acetone extract yielded a hydrocarbon fraction the phenols obtained on hydrolysis of the ex- containing C14-C29 normal paraffins; C24,C26, tractives of S. nigra are present as both esters and C28 wax alcohols; 3,5-stigmastadien-7-one and glycosides. The higher yields of p-hydrox- (tremulone); and β -sitosterol(6). In addition the ybenzoic acid, vanillin, and syringaldehyde in heartwood extractives contained α- and β -amy- the alkaline hydrolysis products suggest that rin, butyrospermol, 24-methylenecycloartanol, these components are present predominantly lupeol, and α-amyrenonol(4). Steam distillation as esters; whereas, the relatively higher yields of the heartwood gave benzyl alcohol, p-ethyl- of vanillic and syringic acids in the acid hydrol- phenol, phenol, β -phenylethanol, n-hexanol, yzates suggest that these acids are present pri- and n-heptanol (3). The methanol extractives of marily as glycosides. P. tremuloides wood were shown to contain The genus Populus includes the aspens phenylalanine, tyrosine, serine, , sinap- and the cottonwoods. Aspen wood when well aldehyde (227) sucrose, glucose, fructose, O- seasoned does not impart odor or taste to food- α-D-glucopyranosyl-(1 →2)-O-β -D- fructofuran- stuffs. Aspen and cottonwood are used for lum- osyl-(1→2)-β -D-fructofuranoside, and traces of ber, veneer, pulpwood, boxes, and crates. xylose and raffinose (291). A spent sulfite liquor Balm-of-Gilead, used in cough medicine, is de- from pulping P. tremuloides was extract- rived from the of balsam poplar. The ex- ed with ether and fractionated to yield several tractives of Populus species bark and wood stereoisomeric forms of syringaresinol and its have been reviewed (197,250). A literature sur- stereoisomer, lirioresinol (271). -40- Figure 29.–Phenylglycosides from Salicaceae.

M 146 182 M 146 183 The n-propanol extractives of Populus tre- lead subacetate, lime, magnesium oxide, am- muloides wood were investigated after alkaline monium hydroxide) used for the isolation of the or acid hydrolysis (272,273,275). The major hy- phenolic glycosides, the benzoyl group at the drolytic product was p-hydroxybenzoic acid. 2-position of the glucose in tremuloidin and sal- Alkaline hydrolysis also yielded syringic acid, icyloylsalicin-2-benzoate (salicyloyltremulo- vanillic acid, syringaldehyde, vanillin, p-hydrox- idin) would migrate to the 6-position to give ybenzaldehyde, and acetosyringone. These populin or salicyloylsalicin-6-benzoate, respec- same components were also found after acid tively. By adjusting the alkalinity of the isolation hydrolysis, but in somewhat different relative procedures, the proportions of these com- amounts. Of the Populus species reviewed, pounds could be changed. These studies made only P. tremuloides extractives gave p-hydrox- suspect all isolations of populin and salicyloyl- ybenzaldehyde on hydrolysis. Because no p- salicin-6-benzoate from Populus and Salix spe- coumaric acid was found in the alkaline hydro- cies in which alkaline purification procedures lyzate, the p-hydroxybenzaldehyde could not were employed (254,255,268,274). be formed from it by oxidative alkaline cleav- The application of polyamide column chro- age, but must have been formed by a reverse matography to bark extractives fractions not aldol from a p-hydroxyphenyl moiety contain- subjected to previous alkaline treatment of any ing an aldol or protected aldol configuration type resulted in isolating bark components that (367) or by hydrolysis of a glycoside or ester. could not be artifacts of isolation procedures. Acid hydrolysis also gave galactose, glucose, The inherent resolving power of the polyamide mannose, and xylose. column technique also resulted in separating The bark of Populus tremuloides has also and isolating many new components that could been investigated extensively. The petroleum not be isolated by procedures used earlier. By ether extractives contained lignoceric acid, lin- this means, 1-O-p-coumaroyl-β -D-glucose was oleic acid, β -sitosterol, ceryl alcohol, glycerol, isolated and demonstrated to be a major com- and an unknown sterol(155). From the physical ponent in the hot-water extractives of Populus properties given, the unknown sterol is proba- tremuloides bark (256). Pyrocatechol was also bly citrostadienol. The methanol extractives isolated. contained pyrocatechol, benzoic acid, vanillic The mass spectral fragmentation pattern acid, p-hydroxybenzoic acid, p-coumaric acid, of salireposide acetate demonstrated conclu- , salireposide, salicin, populin, tre- sively that the structure of salireposide was not muloidin, glucose, sucrose, and fructose (101). hydroxypopulin as accepted for many years, Pyrocatechol has been shown to be the fungi- but was 2-benzoyloxymethyl-4-hydroxyphenyl- static agent from P. tremuloides bark (159). The β -D-glucoside (261). Mass spectral fragmenta- benzene-ethanol extractives contained ben- tion of glucosides of unequivocally known zoic and salicylic acids (156). An arabinan of structures yielded background information that molecular weight 15,000 was found in the could be applied to the structure elucidation of aqueous-methanol extractives (172). Alkaline unknown glucosides (258). hydrolysis of P. tremuloides bark yielded a large Continued development of procedures for amount of p-coumaric acid with lesser amounts isolating components without change from the of ferulic acid, vanillic acid, p-hydroxybenzoic extractives of Populus tremuloides bark re- acid, vanillin, syringaldehyde, acetovanillone, sulted in isolating quantities of salicortin and acetosyringone, and p-hydroxybenzaldehyde tremulacin (264,266) two labile complex glu- (276). Further studies on the hot-water extrac- cosides previously isolated but not character- tives of this bark indicated quantities of salicin, ized by Thieme and coworkers from Salix pur- tremuloidin, and salireposide (251,252,278). In purea bark (348) and P. tremula bark (352), re- addition to these glucosides, salicyl alcohol, spectively. By means of hydrogenolysis and gentisyl alcohol, benzoic acid, sucrose, fruc- acid and alkaline hydrolysis and by infrared, tose, and glucose were identified as important nuclear magnetic resonance, and mass spec- components of these extractives along with mi- trometry, Pearl and Darling (266) proved the nor amounts of mannose and galactose. Pearl structure of salicortin to be the ω-(1-hydroxy-6- subsequently demonstrated that under the in- oxo-2-cyclohexene-1-carboxylic acid ester) of fluence of mild alkaline conditions (e.g., excess salicin and the structure of tremulacin the 2-O-

-42- benzoyl ester of salicortin. Studies on these Propanol extractives of Populus balsami- two labile glucosides suggest that they are the fera wood gave on hydrolysis compounds sim- precursors of salicin, tremuloidin, or populin or ilar to those reported for Salix nigra, except of all three that have been isolated from P. tre- acetovanillone was not found in the alkaline hy- muloides bark. Acid hydrolysis of salicortin drolyzate (272,273,275). The pattern of fatty yields salicyloylsalicin that yields salicin and acids in P. balsamifera bark was investigated by on alkaline hydrolysis. However, gas-liquid chromatography at monthly intervals direct alkaline hydrolysis of salicortin yields sal- for a year (190). The most important com- icin and pyrocatechol with no trace of salicylic pounds were palmitic, oleic, linoleic, linolenic acid. Similarly, acid hydrolysis of tremulacin myristoleic and behenic acids. yields salicyloyltremuloidin that, in turn, will Alkaline hydrolysis of the bark of Populus give salicylic acid, tremuloidin, populin, or all balsamifera yielded the same components as three depending on the alkalinity of the solu- did P. tremuloides bark (276); preliminary eval- tion. Thus apparently many of the compounds uation of the crude hot-water extractives reported in the barks of P. tremuloides (and yielded salicin, salicyl alcohol, and gentisyl al- other Populus and Salix species) were artifacts cohol (278). Polyamide column fractionation of processing procedures. Many flavonoid (270) demonstrated quantities of salireposide compounds were also noted in the polyamide and the glucoside trichocarpin isolated earlier chromatograms of P. tremuloides bark extrac- by Loeschcke and Francksen (208) from P. tri- tives, but were not characterized further. chocarpa bark and proved to be the β-gluco- Propanol extractives of Populus grandi- side of the benzyl ester of . Contin- dentata wood on alkaline and acid hydrolysis ued polyamide column fractionation yielded gave results similar to those obtained with Salix further extractives including 2,6-dimethoxy-p- nigra wood except no ferulic acid was detected benzoquinone, azelaic acid, (272,273,275). Methanol extraction of the wood (257), gentisyl alcohol, trichoside, trichocarpi- gave sucrose, glucose, fructose, O-α-D-gluco- genin (benzyl gentisate) (262) trichocarposide, pyranosyl-(1→2)-O-β -D-fructofuranosyl-(1 →2)- populoside, and dihydromyricetin (263). Tri- β -D-fructofuranoside, and traces of xylose and chocarpigenin, trichoside, and trichocarposide raffinose (291). The bark extractives of this spe- had been isolated previously from P. tricho- cies have received the same attention given to carpa (99,259,260). P. tremuloides (253-255,276-278). If subjected Acetone extraction of the bark of Populus to alkaline hydrolysis the bark extractives balsamifera gave neutral and acidic material yielded the same compounds given by P. tre- (5). Saponification of the neutral material gave muloides, but syringic acid was the major hy- palmitic, palmitoleic, stearic, oleic, linolenic, drolytic product, a situation unique to this spe- 11-eicosenoic, behenic, lignoceric and cerotic cies (276). In early studies of the hot-water ex- acids. Also isolated were the even-numbered tractives of this bark, fractionation yielded all of wax alcohols C18-C26 plus the C27 wax alcohol. the compounds previously reported for P. tre- Saponification of the acidic material gave p-hy- muloides bark plus cis-cyclohexanediol and its droxybenzoic, vanillic, p-coumaric, ferulic, 2-O-p-coumaroyl-β -D-glucoside, grandidenta- caprylic, pelargonic, capric, tridecyclic, palmi- tin (253,277). Interestingly, cyclohexanediol tic, stearic, and arachidic acids. Phenolic alde- has been found in the scent glands of beavers. hydes and ketones were not detected. Controlled acid hydrolysis of P. grandidentata Hydrolysis of Populus deltoides wood pro- bark extractives gave salicyloylsalicin and sali- panol extractives gave results that were identi- cyloyltremuloidin in the same manner reported cal to those obtained with P. grandidentata for P. tremuloides (254,255). Polyamide column (272,273,275). chromatography yielded salicortin and two new Bark extractives of Populus deltoides on glucosides containing the moiety, alkaline hydrolysis yielded the same com- populoside and grandidentoside. Populoside pounds obtained from the other Populus spe- was identified as the ω-caffeoyl ester of salicin, cies, but the green bark did not yield p-hydrox- and grandidentoside was identified as the caf- ybenzaldehyde; the brown furrowed bark did feoyl analog of grandidentatin, cis-cyclohex- (276). Preliminary evaluation of the hot-water anediol-2-O-caffeoyl- β -D-glucoside (97,98). extractives of this bark indicated the presence

-43- of salicin, salireposide, salicyl alcohol, and noted by Smith for P. tremula (328). gentisyl alcohol (278). In addition, polyamide The extractives of Populus heterophylla column chromatographic fractionation yielded bark, if hydrolyzed with alkali, gave the same salicortin, pyrocatechol, grandidentatin, compounds as did the barks of other Populus grandidentoside, populoside, trichocarposide, species, but was the only one of these barks to and 6-methyldihydroquercetin (265). give p-hydroxybenzoic acid as the most impor- Propanol extractives of Populus hetero- tant hydrolytic product (276). Preliminary eval- phyla wood on alkaline hydrolysis gave results uation of the hot-water extractives of this bark qualitatively similar to those from Salix nigra indicated the presence of salicin, salireposide, wood extractives. However, acid hydrolysis salicyl alcohol, gentisyl alcohol, and syringic yielded more vanillic and syringic acids than acid (278). did alkaline hydrolysis suggesting that these C-Glycosyl flavones such as vitexin and or- acids are probably linked glycosidically in the ientin were reported in the leaves of Populus propanol extractives (272,273,275). In contrast, heterophylla; this is the first reported isolation the yield of p-hydroxybenzoic acid from acid of compounds of this type from the family Sali- hydrolysis was much lower than that from al- caceae. A new diterpenoid, heterophyllin, was kaline hydrolysis suggesting that this acid for the major water-soluble extractive of the leaves the most part is ester-linked, a hypothesis first (267).

TILIACEAE

Tilia americana L., American basswood ful pharmaceuticals (48,49). The water extract T. caroliniana Mill., Carolina basswood of the obscure T. alburnum has antispasmodic, T. floridana Small, Florida basswood vasodilative, and cholepoietic properties that T. heterophylla Vent., white basswood were patented (192,193). The genus Tilia is distributed throughout Although was reported to the world. The exact number of species has contain no tannin in the wood and only insignif- been disputed for more than 150 years because icant amounts in the bark (304) the barks of of the variability of the leaf characteristics several Tiliaceae have been used as a (206). Thus the exact number of recognized material. The tannins from European Tiliaceae North American species has varied over the consist primarily of condensed tannins that co- years from 3 to 15. A recent investigation occur with lesser amounts of gallotannins and showed that the variations in Tibia leaf flavon- ellagitannins. oids and the morphological characteristics The chemistry of the extractives from the were continuous across the North American Tiliaceae has been reviewed (143). The com- range of this genus; this suggested the genus pounds characteristic of Tilia species include as represented in eastern tannins, flavonoids, coumarins, triterpenes, should be considered one species, T. ameri- and sterols. Work on American Tilia spp. has cana L. (146). American Indians made thongs, shown the presence of fraxin (286) in twigs rope, string, and thread from the strong inner from T. americana and T. heterophylla and that bark of T. americana. In addition the Indians of fatty acids (67) in the heartwood and the sap- used the bark characteristic of this wood of T. americana. Because of the limited species as well as other Tiliaceae as a remedy work with American species and of the medici- for wounds. Various decoctions of the leaves, nal properties reported for other Tibia species, flowers, bark, and wood are reported in Ameri- the extractives chemistry of T. americana and can folk medicine to have been used for disor- its closely related American species might be ders of the bile and liver (335). Indeed the wood rewarding. of Tilia species is of interest as a source of use-

-44- ULMACEAE (105). is caused by the fun- Celtis occidentalis L., hackberry gus Ceratocystis ulmi; the fungus is carried C. laevigata Willd., sugarberry from tree to tree by the smaller European elm C. lindheimeri Engelm., Lindheimer hackberry bark beetle Scolytus multistriatus and to a C. tenuifolia Nutt., Georgia hackberry much lesser extent by the native elm bark bee- Michx., winged elm tle Hylurgopinus rufipes. The fungus can also U. americana L., American elm spread from diseased to healthy trees by root U. crassifolia Nutt., cedar elm grafts between neighboring elms. Trees af- U. rubra Mühl., slippery elm fected by Dutch elm disease form tyloses that U. serotina Sarg., September elm block water-conducting vessels of the wood, U. thomasii Sarg., rock elm thus killing the tree. In the eastern United States the Ulmaceae Although research on preventing Dutch consist of hackberries and elms. Celtis occi- elm disease has not been fully successful, the dentalis and C. laevigata are the sources of disease is now better understood as are the in- lumber known commercially as hackberry. tricate relationships between the host tree and Most of this lumber is used for furniture and the beetle and fungus that attack it. Thus meth- some for various types of containers. The elms ods that apparently have promise in controlling were considered an excellent wood for houses Dutch elm disease include the early (but still and boats by both the American Indians and necessary) control methods-removing the dis- the English settlers. The Indians fashioned can- eased tree and using insecticides to control the oes from the bark of and beetle (50,310). The control methods also in- stopped the cracks with the crushed bark of U. clude the possibility of using repellant chemi- rubra. The inner bark of U. rubra has been cals that deter beetle feeding and are derived chewed as a soothing remedy and used as a from tree species not attacked by the beetle laxative and an emollient for external inflama- (13,119,120,240-243); using systemic fungi- tion (187). For commercial purposes the elms cides, e.g., benomyl and lignasan (290,327); are divided into two categories: Hard (rock) and using (sex attractants) elic- elms (U. alata, U. crassifolia, U. serotina, and U. ited by the female beetle for baiting traps thomasii) and the soft elms (U. americana and (248,249,366). U. rubra). Other uses of elm lumber are for man- Because of the intricate relation of extrac- ufacturing boxes and crates and furniture. A tives chemistry to Dutch elm disease, the ex- poultry farmer told us that using bedding of elm tractives of the elms are important. Elm wood leads to high mortality for turkeys, but not for extractives (197) and the extractives chemistry . Elm wood can cause woodcutter’s of the Ulmaceae (143) have been reviewed. The eczema; the leaves have irritant hairs on their general chemistry of the bark has been investi- undersurfaces (386). gated (55). The characteristic compounds iso- The extractives chemistry of Celtis species lated thus far from this family include a muci- has not been studied in detail. Preliminary work lage from the bark, flavanoids, tannins, lignans showed that the wood and the bark of C. laevi- (table 4) aromatic sequiterpenes (table 5), ster- gata were almost devoid of any phenolic ex- ols, and triterpenes. The structure of the bark tractives. Only triterpenoid acids, fatty acids, mucilage of Ulmus rubra has been studied and glucose were detected (316). These find- (26,27) as has the obtained from ings contrast with those for C. australis bark U. americana wood (121). Although neither the that contained betulin, 3,3´-di-O-methylellagic wood nor the bark of the Ulmaceae reviewed acid and its glycoside, gallic acid, and que- here was reported to contain significant brachitol(56). amounts of tannin (304); the bark of C. occiden- The American elms are threatened by two talis has been used as a , and that of the diseases, phloem necrosis and Dutch elm dis- elms at one time as a source of dyes and tan- ease. Phloem necrosis is apparently caused by nins (221). The bark tannins of European elms mycoplasma bodies; the symptoms are sup- contained leucoanthocyanidins and catechin pressed by injecting tetracycline, an antibiotic units (21).

-45- Table 4.—Lignans in Ulmus heartwood Ulumus species1 Compound alata americana crassifolia rubra serotina thomasii Thomasic Acid (1) + – ± – + +++ Thomasidioic Acid (2) + – – –± + Lyoniresinol(3) ± – ± – + +++ ( + )-Lyoniresinol-2a- O-rhamnoside (4) + – + – ++ ++ 1 –, Not detected; ±, possibly minute amounts; + , small amounts; + + , moderate amounts; + + + , major amounts.

Table 5.—Sesquiterpenes in Ulmus heartwood Ulmus species1 Compound alata americana crassifolia rubra serotina thomasii 7-Hydroxycadalenal(1) – – ± +++ – – 7-Hydroxy-3- methoxycadalenal(2) – – – + – – 7-Hydroxycadalene (3) – + – + – ± (-)-7-Hydroxycalamenenal (4) ± – ±++– – (-)-7-Hydroxycalamenene (5) + + + + + ++ ++++++ Mansonone C (6) – ++ ± – + ± 1 –, Not detected; ± , possibly minute amounts; + , small amounts; + + , moderate amounts: + + + , major amounts.

The extractives of Ulmus thomasii heart- masic acid. The original structure proposed for wood contained the lignans (table 4) thomasic thomasic acid (312) responsible for the fluo- acid, thomasidioic acid, lyoniresinol, and ( + )- rescence of wet U. thomasii wood, was revised lyoniresinol-2a- O-rhamnoside (157,312), as (157,370). well as 6-hydroxy-5,7-dimethoxy-2-napthoic Furniture manufacturers have repeatedly acid (59) 6-hydroxy-3-hydroxymethyl-5,7-di- experienced difficulties with a yellow-colored methoxy-2-napthoic acid lactone (59), and 2,6- stain in their finishes on Ulmus rubra wood. dimethoxy-p-benzoquinone (157). The nap- (See cover) This yellow color will even migrate thoic acids and the benzoquinone can be re- into vinyl plastic overlays. Research on this garded as in vivo cleavage products of tho- staining showed that the compound responsi-

-46- ble for the yellow discoloration was the new, li- reported to stimulate feeding of the smaller Eu- pophilic sesquiterpene, 7-hydroxycadalenal. ropean elm bark beetle. Interestingly, juglone, This compound is accompanied by a series of which can be isolated from shagbark hickory related sesquiterpenes, 7-hydroxy-3-methoxy- (Carya ovata), as well as other napthoquinones cadalenal, 7-hydroxycadalene, and (-)-7-hy- deter bark beetles from feeding (120,240-242). droxycalamenenal (106). The yellow stain is Chemical deterrents to elm bark beetle feeding deepest in outer heartwood. Bleaching the have also been found in another nonhost tree, wood with peroxide oxidizes the yellow sesqui- the white oak (Quercus alba) (119). Several terpene found at the wood surface to a color- sugars in elm bark failed to stimulate feeding less compound. However, because of the slight (243). volatility of the sesquiterpene, the yellow stain The elm bark beetle aggregation phero- returns as sesquiterpene slowly migrates from mone is composed of three components: (-)-4- the interior of the wood to the wood surface. 7- Methyl-3-heptanol; 2-endo,4-endo-dimethyl- Hydroxycalamenene, first isolated from U. tho- ethyl-6,8-dioxabicyclo[3.2.1]octane (multistria- masii (302) apparently is ubiquitous in elm tin); and (-)-α-cubebene (249). α-Cubebene is a heartwood (303). Mansonone C has also been naturally occurring sesquiterpene in elm bark. detected in heartwood of various elms (303). Structurally multistriatin, the synthesis of which 7-Hydroxycalamene and 7-hydroxcada- was recently reported (53) is closely related to lene were found toxic to many micro-organisms frontalin, an aggregating of the and are produced in Ulmus americana in re- southern beetle (228) and brevicomin, the sponse to wounding (15). The total phenolic principal component of the western pine beetle content among the various elm species can ap- pheromone (23). Bait tests with a mixture of the parently be correlated with their susceptibility synthetic pheromones of elm bark beetle (mul- to Dutch elm disease (303). The free sterols tilur) have been successful in Europe (366). found in Ulmus thomasii heartwood contained This Review concludes with the elms. This large amounts of sitosterol, and smaller is fortunate because the research on this spe- amounts of cholesterol, campesterol, stigmas- cies, especially the inclusion of Dutch elm dis- terol, 24-methylenelophenol, and citrosta- ease, exemplifies the intricate relationships dienol. The free sterols of U. rubra were similar that wood and bark extractives can have in uti- except 24-methylenelophenol was not de- lization and preservation of trees. The work on tected. The esterified sterols from U. rubra were this species also demonstrates a need for - mostly sitosterol and citrostadienol with lesser ther research in extractives chemistry. amounts of the other sterols except stigmas- Acknowledgments terol. Sitosterol and campesterol also were The authors gratefully acknowledge the found in U. americana (303). Saponification of following: Dr. Irwin A. Pearl, Institute of Paper the esters obtained from U. rubra heartwood Chemistry, Appleton, Wis., for preparing a re- gave wax alcohols, fatty acids, and dolichols view of wood and bark extractives of Populus (dihydro-cis-betulaprenol-5) in addition to the and Salix species of eastern United States; various sterols mentioned (106). This was the Prof. C.-L. Chen, North Carolina State Univer- first reported occurrence of dolichols in a plant sity, Raleigh, N.C., for his invaluable comments species. on the section dealing with the Liriodendron tu- The extractives in the bark of Ulmus amer- lipifera; Mrs. Lida W. McBeath, Publications Ed- icana have been investigated with particular itor, and Mrs. Marilyn A. Diehl, , both of emphasis on Dutch elm disease. Thus lupeyl the U.S. Forest Products Laboratory for expe- cerotate and catechin-7-β -xylopyranoside diting publication of the manuscript. (86,89) as well as friedelan-3β -ol (12) have been

-47- Literature Cited

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