Ethnobotany, Pharmacology and Phytochemistry of the Genus Lamium (Lamiaceae)

FABAD J. Pharm. Sci., 31, 43-52, 2006

SCIENTIFIC REVIEW

Ethnobotany, Pharmacology and Phytochemistry of the Genus Lamium (Lamiaceae) Summary The genus Lamium (Lamiaceae) is represented by 30 species in the flora of Turkey. Lamium album, L. maculatum and several Lamium species have been used in Anatolian folk medicine. In this study, the genus Lamium is evaluated from the viewpoint of ethnobotany, pharmacology and phytochemistry. Key Words: Lamium, Lamiaceae, dead nettle. Received : 15.02.2007 Revised : 25.06.2007 Accepted : 05.07.2007

INTRODUCTION

A member of the Lamiaceae family, Lamium L. (dead stinging nettles, but unlike those, they do not have nettle), has been described as perennial and annual stinging hairs and as such are harmless or apparently herbs. Leaves are ovate to reniform, crenate to dentate. "dead". Some Lamium plants have been used in folk Verticillasters are dense or remote, 2-12 flowered. medicine worldwide as remedy in the treatment of Calyx is tubular or campanulate, 5-veined, with 5 several disorders, such as trauma, fracture, paralysis, equal or subequal teeth. Corolla is purple mauve, hypertension, menorrhagia, and uterine pink, cream or rarely white, 2-lipped; upper lip hood- hemorrhage3,4. ed; lower lip obcordate or broadly obovate with or without small lateral lobes. Nutlets are triquetrous, The focus of this review is to provide information of usually truncate at apex1. the ethnobotanical uses and pharmacological activities The genus Lamium contains almost 40 species, native of Lamium species and the structures of the compounds to Europe, Asia, and North Africa2, some of which isolated and identified from Lamium since 1967. are well-known: L. album L., L. purpureum L., and L. maculatum L. The common name “dead nettle” Ethnobotanical uses and pharmacological activities refers to their superficial resemblance to the unrelated of Lamium species

* Hacettepe University, Faculty of Pharmacy, Department of Pharmacy Management, TR-06100, Ankara, Turkey ** Hacettepe University, Faculty of Pharmacy, Department of Pharmacognosy, TR-06100, Ankara, Turkey ˚ Corresponding Author: e-mail: [email protected]

43 Traditional medicinal uses of Lamium have been I. Iridoids and secoiridoids reported. L. album is considered as the most popular species. The dried flowers of this plant exhibited The most prominent compounds in Lamium species uterotonic, astringent, antispasmodic and anti- are iridoid glucosides. Lamium species contain C10 or inflammatory activities and therefore are utilized in C9 iridoids. The C10 cyclopentane pyrane ring is menorrhagia, uterine hemorrhage, vaginal and cervi- usually characterized by a 11–COOR (1-15, 21) or 4 cal inflammation and leukorrhea treatment . L. mac- 11–CH3 (16-20) substitution. One of the earlier phy- ulatum has been used in Chinese folk medicine in the tochemical reports on the phytochemistry of Lamium treatment of trauma, fracture, paralysis, and species revealed the isolation of two iridoid glucosides, hypertension5. L. album flowers have been reported lamiol (16) and lamioside (17), from Lamium to possess antioxidant, free radical scavenging and amplexicaule15; however, today over 20 iridoids have antiproliferative properties6-8. L. purpureum flowers been isolated and identified from Lamium species. also exhibited antioxidant and free radical scavenging Iridoids are also recognized as valuable taxonomic activities7. The essential oil from L. garganicum L. markers for the genus16. Deacetylasperulosidic acid subsp. laevigatum Arcangeli was reported to possess (21), characterized from L. amplexicaule17, is the only bacteriostatic activity against Gram-positive and - representative of a C-11 carbocyclic iridoid isolated negative bacteria9. Of the 30 species growing in the from a Lamium species to date. The remainder of the 1,10 flora of Turkey , the whole plants of L. album and related iridoids are substituted by a COOCH3 function some other Lamium species are used to relieve pain at C-4 position. As in dehydropenstemoside (13) and in rheumatism and other arthritic ailments in Western deacetyl asperulosidic acid (21), a double bond can Anatolia11, and L. album, L. maculatum, and L. pur- take a place between C-7/C-8 carbon atoms or this pureum have been reported to be used as tonics and position is occupied by an epoxy function, as in in the treatment of constipation as home remedies12. sesamoside (14). 6-O-syringyl-8-O-acetylshanzhiside Different extracts prepared from the over ground methyl ester (12) isolated from L. garganicum subsp. 18 parts of L. eriocephalum Bentham subsp. eriocephalum, laevigatum is the only example of the Lamium iridoids L. garganicum subsp. laevigatum, L. garganicum L. with further esterification at C-6 position. To date, subsp. pulchrum R. Mill., and L. purpureum L. var.Lamium species have been reported to contain iridoids purpureum exhibited anti-inflammatory13, with a β hydroxylation at C-5, 6, 7 or 8 atoms. How- antinociceptive13, antimicrobial14, and free radical ever, lamerioside (6) reported from L. eriocephalum scavenging14 activities. subsp. eriocephalum19, an a-epimer of a well-known iridoid, lamiide (7), is the first example of a Lamium Phytochemistry of Lamium species iridoid with an α-C-7(OH) function. C9 iridoids had more restricted distribution within the genus Lamium. The medicinal properties of Lamium species and their Harpagide (22) and 8-O-acetylharpagide (23), isolated traditional usage worldwide have attracted significant from L. galeobdolon L. subsp. galeobdolon17, are the attention and this has led to intensive phytochemical only C9 iridoids isolated from Lamium plants. Almost investigations. The phytochemistry of the genus La- all Lamium iridoids are monoglucosidic compounds mium has been extensively studied since 1967. During with a β-glucopyranose moiety linked to C-1 position. the past 40 years, iridoids and secoiridoids, phenyl- However, recently Yalç›n and co-workers19 reported propanoids, flavonoids, anthocyanins, phytoecdys- the isolation of eriobioside (15) from L. eriocephalum teroids, betaines, benzoxazinoids, terpenes, and me- subsp. eriocephalum . This is the first iridoid diglyco- gastigmen compounds as well as essential oils have side to be isolated from the genus Lamium character- been recognized from Lamium species. Structures of ized by the occurrence of a gentiobiosyl moiety on the compounds are given in Figures 1-5. Table 1 lists its structure. the compounds reported in Lamium, including the species from which they have been isolated. The secoiridoid glucosides, albosides A (24) and B

44 FABAD J. Pharm. Sci., 31, 43-52, 2006

(25) isolated from a Danish population of L. album20, A has a structure of sweroside-type, whereas Alboside are the only examples of the secoiridoids reported B is a morroniside-type secoiridoid glucoside (Fig. 1, from a plant belonging to the genus Lamium. Alboside Table 1).

1 R5= OH R6= H R7= H R8= OH 2 R5= OH R6= H R7= H R8= OAc 3 R5= OH R6= OH R7= H R8= OH 4 R5= H R6= H R7= OH R8= OH 5 R5= H R6= OH R7= OH R8= OH 6 R5= OH R6= H R7= α-OH R8= OH 7 R5= OH R6= H R7= OH R8= OH 8 R5= OH R6= H R7= OH R8= H 9 R5= OH R6= OH R7= H R8= H 10 R5= H R6= OH R7= H R8= OH 11 R5= H R6= OH R7= H R8= OAc 12 R5= H R6= O-syringyl R7= H R8= OAc

13 14 15

22 R= H 16 R5= OH R6= OH R8= OH 21 23 R= Ac 17 R5= OH R6= OH R8= OAc 18 R5= H R6= OH R8= OH 19 R5= H R6= OH R8= OAc 20 R5= OH R6= H R8= OAc

Figure 1. Iridoids and secoiridoids from Lamium 24 25

45 Compounds found in Lamium species

46 1. Table FABAD J. Pharm. Sci., 31, 43-52, 2006

II. Phenylpropanoids and colleagues24 reported the isolation of five new phenylethanoid glycosides, lamiusides A-E (27, 29- Phenylpropanoids isolated from Lamium species are 32), together with four known phenylethanoid glyco- given under the following titles: sides (26, 33-35) from the whole plants of L. purpureum. However, lamiuside A (27) is identical to that 21 IIa. Phenylethanoid glycosides of lamalboside, previously isolated from L. album . The phenylethanoid glycosides isolated from Lamium In previous reports, three phenylethanoid glycosides, species are all di- or triglycosidic compounds. In verbascoside (= acteoside: 3,4 dihydroxy-β- lamiuside C (30) and isoacteoside (34), the acyl moiety phenyletoxy-O-α-rhamnopyranosyl-(1→3)-4-O- was attached to the C-6' position of the core glucose; caffeoyl-β-glucopyranoside) (26), lamalboside (27) however, in the remaining glycosides, the acyl unit and cis-acteoside (28) were reported from L. album21, was linked to C-4' carbon atom of the core sugar (Fig. L. garganicum17, L. maculatum L. var. kansuense22, 2, Table 1). 23 L. maculatum L. , and L. purpureum17. Recently Ito

26 R1= H R2= H R3= H 27 R1= H R2= H R3= β-galactopyranosyl 29 R1= H R2= CH3 R3= β-galactopyranosyl 31 R1= OCH3 R2= H R3= β-galactopyranosyl 33 R1= H R2= CH3 R3= H

28 R1= H R2= H R3= cistine-caffeic acid 32 R1= CH3 R2= β-glucopyranosyl R3= cistine ferulic acid 30 R= β-galactopyranosyl 35 R1= CH3 R2= β-glucopyranosyl R3= transtine-ferulic acid 34 R= H

38 Figure 2. Phenylethanoid glycosides and phenylpropanoids from Lamium species.

47 IIb. Monomeric and dimeric phenylpropanoids

Lamium species contain some monomeric or dimeric phenylpropanoids. Salidroside (36) was reported from L. galeobdolon subsp. galeobdolon17 and chlorogenic acid (37) was isolated from L. album21. In addition to these monomeric phenylpropanoids, a dimeric phenylpropanoid glucoside, liriodendrin (38), has been characterized from L. maculatum var. kansuense38. Liridodendrin is the only lignan glycoside reported 39 R3= β-glucopyranoside R3'= H in the genus (Fig. 2, Table 1). 40 R3= 6"-α-rhamnosyl-β-glucopyranoside R3'= OH 41 R3= 6"-α-rhamnosyl-β-glucopyranoside R3'= OCH3 42 R3= β-glucopyranoside R3'= OH IIc. Flavonoids 43 R3= 6"-coumaroyl-β-glucopyranoside R3'= H 44 R3= 6"-coumaroyl-β-glucopyranoside R3'= H 45 R3= α-rhamnoside R3'= H To date, seven flavonol glycosides, kaempferol 3-O- glucoside (39), rutoside (40), 3’-O-methyl quercetin 3-rutinoside (41), quercetin 3-O-glucoside (42), trans- tiliroside (43), cis-tiliroside (44), quercitroside (45) and a flavonol, 3,7-dimethoxy quercetin (46), have been obtained from the flowers of L. album21, L. maculatum var. kansuense22,38, and L. maculatum23 (Fig. 3, Table 1).

IId. Anthocyanins

A total of eight anthocyanins were variously identified from the fresh flowers of L. amplexicaule, L. garganicum, L. grandiflorum, and L. maculatum25. Five of the anto- cyanins were cyanidin derivatives (47-51) and three were peonidin glycosides (52-54). Anthocyanins with malonyl residues attached to the glucose in the 5- position are unique to Lamiaceae25. Two of the Lamium anthocyanins wer e substituted with a malonyl moiety at C-5(OH) (49), or on the C-3 of the glucose unit (54), whereas two glycosides (51, 53) wer e malonylated both at C-5(OH) and C-3 of the glucose moiety. Two of the cyanidin glycosides (49, 50) wer e coumaroyl R = CH R = CH R = OH substituted. Of the eight anthocyanins, two (48, 52) 46 3 3 7 3 3' 47 R3'= H R5= H R6"= H R = H R = β-glucopyranoside R = H wer e isolated as cyanidin and peonidin diglucosides 48 3' 5 6" 49 R3'= H R5= 6'"-malonylglucopyranside R6"= coumaroyl (Fig. 3, Table 1). 50 R3'= H R5= β-glucopyranoside R6"= coumaroyl 51 R3'= H R5= 6'''-malonyl glucopyranoside R6"= malonyl 52 R3'= OCH3 R5= β-glucopyranoside R6"= H R = OCH R = 6'''-malonyl glucopyranoside R = malonyl III. Steroids 53 3' 3 5 6" 54 R3'= OCH3 R5= β-glucopyranoside R6"= malonyl

IIIa. Phytoecdysteroids

Phytoecdysteroids are insect hormone analogues Figure 3. Flavonoids and anthocyanins from Lamium species.

48 FABAD J. Pharm. Sci., 31, 43-52, 2006 secreted by some plant species. They constitute a IV. Hemiterpenes qualitative defense against phytophagous insects. Lamium species are considered as ecologically impor- There is only one report which implies a hemiterpene tant hosts for a number of insect species, e.g. L. album glucoside, hemialboside (64), was isolated from Lami- and L. purpureum ar e hosts on which the lepidopterans um album43 (Fig. 4, Table 1). Arctica caja, euplagia quadripunctaria and Phragmatobia fuliginosa feed26. Based on the investigations on plant V. Megastigmens phytoecdysteroids, six ecdysteroids (55-60) were 23,26 reported from L. album26, L. maculatum , L. macu- Sarker and co-workers27 isolated and characterized 17 latum var. kansuense22,38, and L. purpureum (Fig. 4, a novel “megastigmen” class of glycoside, 9-O-β-D- Table 1). glucopyranosyloxy-5-megastigmen-4-on (65) from the leaves of Lamium album (Fig. 4, Table 1). IIIb. Sterols VI. Nitrogen-containing compounds Deng et al.22 reported β-sitosterol (61), daucosterol (62) and stigmasterol (63) from L. maculatum var. There are a few reports on the isolation and identifi- kansuense (Fig. 4, Table 1). cation of some nitrogenous compounds from some Lamium species.

55 R1= H R2= OH R3= H R4= OH R5= CH3 56 R1= OH R2= OH R3= H R4= OH R5= CH3 57 R1= H R2= OH R3= OH R4= OH R5= CH3 58 R1= H R2= OH R3= H R4= H R5= CH2OH 59 R1= H R2= OH R3= OH R4= H R5= CH3 60 R1= H R2= OH R3= OHa R4= H R5= CH3

61 R= H 63 62 R= β-glucopyranoside

64 65

Figure 4. Steroids, terpenes and megastigmens from Lamium species.

49 VIa. Benzoxazinoids proline betaines28,29,44 (73, 74) from L. album, L. purpureum, L. maculatum, and L. galeobdolon, as well Benzoxazinoids are arylhydroxamic acid derivatives as a different type of betaine, trigonellin29,44 (75), and play a role in the protection of plants against were isolated and identified (Fig. 5, Table 1). bacteria, fungi and insects in many crop plants. Ali- pieva and colleagues17 reported the isolation of five VIc. Miscellaneous benzoxazinoids (66-70) from L. galeobdolon subsp. galeobdolon (Fig. 5, Table 1). Two nitrogen-containing compounds with miscellaneous structure, allantoin (76) and uridine (77), were VIb. Betaines isolated and identified from L. maculatum var. kansuense22,38. Betaines are naturally occurring compounds that have an important role in osmotic stress resistance in a VII. Essential oils variety of organisms, including bacteria, algae, mam- mals, and plants28. Betaines are also being considered Although Lamiaceae family plants are known to as taxonomic markers for some plant families29. To contain a high rate of essential oils, the plants from date, two pipecolic acid derivative betaines29,44 (71, the genus Lamium belonging to the subfamily 72) from L. maculatum and L. galeobdolon and two Lamioideae45 contain a small amount of essential oils.

66 R2= β-glucopyranosyl R4= H R6= H R7= H 67 R2= β-glucopyranosyl R4= H R6= OH R7= H 68 R2= β-glucopyranosyl R4= H R6= H R7= OH 69 R2= β-glucopyranosyl R4= OH R6= H R7= H 70 R2= H R4= OH R6= H R7 = H

73 R= H 75 71 R1= H R2= H 74 R= OH 72 R1= OH R2= H

76 77

Figure 5. Nitrogen-containing compounds from Lamium species.

50 FABAD J. Pharm. Sci., 31, 43-52, 2006

The yields of the essential oils obtained from the fresh which contain a C10 or C9 skeleton. Moreover, the flowers of Lamium plants vary between 0.01-0.31% iridoid glucosides were consider ed as chemotaxono- (9,30-32). The earliest study was realized on L. pur- mic markers of the genus Lamium. pureum essential oil, which showed 1-octen-3-ol, hexen-1-ol, phenethyl alcohol, benzyl alcohol, phenol, The collected data provides a means to understand o-, m- and p-cresols, guaiacol, eugenol, and fatty acids the latest developments in the pharmacology and as main components30. In another study, L. garganicum phytochemistry of the genus. The information sum- subsp. laevigatum Arcangeli was examined by GC and marized here is intended to serve as a tool to scientists GC/MS, and 1,8-cineole (47.5%), citronellal (25.1%) in the fields of ethnopharmacology and natural prod- and isoeugenol (11.8%) were found to be the major ucts chemistry. compounds9. In a comparative study on the essential oils of four Lamium species from Bulgaria, the essential oils obtained from L. album, L. purpureum, L. garganicum, and L. maculatum flowers collected from nine REFERENCES populations were analyzed by GC/MS. A similarity 1. Mill RR. Lamium L., Davis PH (ed.), Flora of of the volatile profile of all samples was shown. Turkey and the East Aegean Islands, University Qualitative and quantitative differences in the oil Press, Edinburgh, Vol. 7, 126-148, 1982. composition of plants collected at different locations 2. Willis A. Dictionary of Flowering Plants and were observed. However, all studied samples con- Fern, 8th edition, Cambridge University Press, tained significant amounts of hydrocarbons with C 12 Cambridge, 624-626, 1973. to C carbon atoms exclusively with straight chains 31 3. Weiss RF. Herbal Medicine, Beaconsfield, 313- and fully saturated31. The essential oils of L. purpureum, 314, 1988. and were ana- L. hybridum, L. bifidum L. amplexicaule 4. Bisset NG. Herbal Dr ugs and Phytopharmaceu- lyzed by GC-MS and SPME, respectively. All these ticals: A Handbook for Practice on a Scientific essential oils were characterized by their high contents Basis. Scientific Publishers, Stuttgart, 288-291, of germacrene D. In (35.4%), L. purpureum L. hybridum 1994. (39.0%) and (34.9%), it was the main com- L. bifidum 5. Shuya C, Xingguo C, Zhide H. Identification and pound, while in (28.9%), the main L. amplexicaule determination of ecdysone and phenylpropanoid compound was trans-chrysanthenyl acetate (41.1%)32. glucoside and flavonoids in Lamium maculatum by capillary zone electrophoresis, Biomed. Chro- CONCLUSION matogr., 17, 477-482, 2003. 6. Trouillas P, Calliste C-A, Allais D-P, Simon A, species, commonly called dead nettles, have Lamium Marfak A, Delge C, Duroux J-L. Antioxidant, been used in folk medicine worldwide as remedy in anti-inflammatory and anti-proliferative proper- the treatment of several disorders, such as trauma, ties of sixteen water plant extracts used in the fracture, paralysis, hypertension, menorrhagia, and limousin countryside as herbal teas, Food Chem., uterine hemorrhage. The interest due to the medicinal 80, 399-407, 2003. properties of species has led to intensive Lamium 7. Matkowsi A, Piotrowska M. Antioxidant and free phytochemical investigations on the plants. As a result radical scavenging activities of some medicinal of these phytochemical investigations, several iridoids plants from Lamiaceae, Fitoterapia, 77, 346-353, and secoiridoids, phenylpropanoids, flavonoids, an- 2006. thocyanins, phytoecdysteroids, betaines, benzoxazi- 8. Paduch R, Wójciak-Kosior M, Matysik G. Inves- noids, terpenes, and megastigmen compounds as tigation of biological activity of Lamii albi flos well as essential oils have been recognized from extracts, J. Ethnopharmacol., 110(1), 69-75, 2007. different species. The most prominent com- Lamium 9. Roussis V, Chinou I, Perdetzoglou D, Loukis A. pounds in species are the iridoid glucosides, Lamium Identification and bacteriostatic activity of the

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