J. Japan. Soc. Hort. Sci. 50(2) : 262-269. 1981.

Comparative Studies of Condensed from Several Young Fruits

Tomoaki MATSUO and Saburo IToo

Faculty of Agriculture, Kagoshima University, Korimoto, Kagoshima 890

Summary Four polymeric tannins prepared from young fruits of persimmon, banana, carob bean and Chinese quince were shown, in addition to having some properties of con- densed tannins, to produce precipitate in methanolic solution by addition of K2HPO4, to form on acid treatment, and to release the thioethers of -3- ols by means of toluene-a-thiol treatment. It is suggested from these results that each is a polymer and should be called flavanan or flavonan tannin instead of . Among the fruit tannins tested, loquat-tannin was an exception; it appeared to be a proanthocyanidin oligomer. Three methylated tannins from young fruits of banana, carob bean and Chinese quince were similar in molecular size (Mw=1.4-1.0 x 104, Mn=0.7-0.2 x 104), while methylated kaki-tannin is thought to be a slightly higher polymer. In comparison with kaki-tannin which mainly consists of , catechin-3- gallate, gallocatechin and gallocatechin-3-gallate with the ratio of about 1 : 1.2 2.1 :2.2, banana-tannin consists of catechin and gallocatechin with the ratio of about 1 to 1.3 and carob bean-tannin consists of catechin-3-gallate, gallocatechin and gallocatechin-3-gallate with the ratio of about 1 : 3.3 : 4.6. Chinese quince- and loquat-tannin appear to be composed of only catechin.

and recently established a simple and rapid Introduction purification method applicable to condensed In some species, immature or young fruits tannins in several astringent fruits (9). In have remarkable astringency, for example, addition, we found that toluene- x-thiol was banana and persimmon. It is generally known an excellent reagent for degradation of a poly- that astringency in fruits is caused by conde- meric proanthocyanidin such as kaki-tannin nsed or conjugated tannins (17, 20). These (8). terms, however, appear to be arbitrarily used Chemical comparison of four condensed without clear chemical definition. In some tannins prepared from different astringent reports, researchers described condensed tan- fruits (banana, Chinese quince, loquat and nins as immobile polyphenolic compounds on carob bean) with kaki-tannin from persimmon thin layer and paper chromatographies (10). fruit is described in the present paper. Technical problems in the past have impeded Materials and Methods researchers from developing a good purification materials procedure for condensed tannins and adequate methods to degrade the purified tannins to Young persimmon fruits (Diospyros kaki their constituent (s) to elucidate their chemical Thunb., cv. "Hiratanenashi", astringent type) structures. were harvested from July to August in 1977 We have investigated chemical structures and 1978 at Toso Orchard of Kagoshima Uni- and properties of kaki-tannin, an astringent versity. Loquat fruits (Eriobotrya japonica component in immature persimmon fruit Lindl., cv. "Mogi") were harvested in March, known to be a typical condensed tannin (8), 1977 at Tarumizu Fruit Experiment Station of Kagoshima Prefecture. Carob beans (Cera- Received for publication March 23, 1981 tonia siliqua L.) were a gift from Mr. K. Y.

262 MATSUOAND IT00 : STUDIESOF C 0 NDE NSEDTANNINS FROM YOUNG FRUITS 263

Ogawa, Pasadena, California and were har- tribution were analyzed by gel permeation vested on April 9, 1978. Chinese quince (Chae- chromatography. High pressure liquid chro- nomeles sinensis Koehne) and banana (Musa matography analysis was performed under the sapientum L.) were harvested in Kagoshima following conditions; column; TSK G5, 4, 3. Prefecture, in June and August of 1978, re- 2 H 6, 7.5 X 600 mm, mobile phase; THF, flow spectively. All individual fruits were leaf- rate; 1.0 ml/min, detection; UV at 280 nm, green. The average fruit weights were the instrument; Waters LC. Polystylenes with same as those reported in our previous paper various polymerization degrees were used as (9). Fruits and tissues were stored in a standard markers for the molecular weight. freezer, or dipped in after cutting Mw and Mn express weight average molecular into small pieces and stored at -20°C until weight and number average molecular weight, use. respectively. Analytical methods of condensed tannins Results The four condensed tannins were prepared by the same procedure described in the previous Preparation of condensed tannins from paper (9). Powders of each tannin obtained several young fruits were lyophilized and stored at -20°C until Condensed tannins were prepared from each chemical analysis. Preparation, acid degrada- of the five kinds of astringent young fruits by tion and toluene-a-thiol degradation of each means of the K2HPO4-precipitation method condensed tannin were carried out in the same described in the previous paper (9). The manner as that in the previous paper (8). For yield, purity and some properties were already identification of deep red pigments produced reported in the paper. Persimmon and carob by acid degradation of each tannin, ascending bean gave 2.0 and 1.9 percent of tannin yields. paper chromatography was performed using While banana and Chinese quince showed Toyo no. 51 filter paper. The developing sol- relatively lower contents of condensed tannin vents employed were; ( i ) acetic acid-HCl- (0.6 and 0.4 percent). Young loquat fruits water=30:3:10, v/v, AHW, (ii) n-butanol- were less astringent and differed from the acetic acid-water=4:1:5, v/v, upper phase, others in that it did not precipitate when K2 BAW, and (iii) 88% formic acid-HCl-water HPO4 was added to the methanolic extract. =5:2:3, v/v, FHW. The major component, proanthocyanidin, was Polyphenolic products released by toluene- detected in the butanol-soluble fraction using a-thiol treatment from each tannin were ana- the HCI-BuOH test. In this experiment the lyzed with thin layer chromatography using purified loquat-tannin was prepared by high precoated silica gel G-60 plates (Merk Co.). porous polymer chromatography with a eth- Solvents used here were: (A) CHCl3-EtOAc- anol-water gradient from 5% to 50%. The f ormic acid = 2 :1:1, v/v, (B) CHC13-EtOAc- yield was 0.48g per 100g of fresh tissue. AcOH=2:1:1, v/v, (C) benzene-AcOH-water Acid degradation of condensed tannins =10:10:1, v/v. The reagent sprays used for All of the five condensed tannins produced visualization were (a) Folin-Ciocalteu reagent some red pigment (s) when treated with 2 N and (b) 10% vanillin in ethanol-HCI. The HCl in a boiling water bath for 60min. The quantitative ratio of pigments or polyphenolics pigment products were examined by paper formed from each tannin was determined from chromatography and cellulose-TLC with three the surface area of the spots on chromato- different solvent systems (i, ii and iii) and grams. The area of each spot was determined identified by comparing their Rf values and by means of a Shimazu DB scanner using a spectrophotometric properties with the data of zigzag scanning mode, after coloration with Harborne (3). The quantitative ratio of the HCI-vanillin reagent (AR=700 nm, A5=530 or pigments produced from a tannin was calcu- 520 nm). Each tannin was methylated by the lated roughly by means of measuring the modified Hakomori's method twice or three surface area of the red spots on cellulose times. Their molecular weight and its dis- plates. 264 JOURNAL OF THE JAPANESE SOCIETY FOR HORTICULTURAL SCIENCE

Table 1. Rf values and spectrophotometric properties of red pigments derived from several condensed tannins

Table 2. Chromatographic identification of products given from several condensed tannins by toluene-a-thiol treatment

Table3.Quantitativeratioofsomeflavan-3-olsconstitutedeachcondensedtannin

Kaki-tannin obtained from young persim- one pigment, designated as Q-1 and L-1 in mon fruit produced two distinct pigments, Table 1. Banana-tannin produced two pig- which had already been identified as delphini- ments with a ratio of about 1 to 1, in addition din and . The quantitative ratio lof to a trace of another pigment. They were both pigments was about 1 to 3 (8), Chinese designated as B-1, B-2 and B--3 in increasing quince-tannin and loquat-tannin yielded only order of amount. Carob bean-tannin gave MATSUO AND IT00 : STUDIES OF CONDENSE D TANNINS FROMYOUNG FRUITS 265 one major pigment and a trace of another, catechin and gallocatechin-3-gallate with the designated as C-1 and C-2. All five condensed ratio of about 1 to 3.3 to 4. 6, in addition to tannins also produced amorphous and red- a trace of catechin-like substance. brown -like substances as well as These results are very consistent with the deep red pigments, observed evidently as a results obtained from examina- broad tailing line near the origin on cellulose- tion, considering the chemical properties of thin layer chromatograms. proanthocyanidin B groups (4) . That is, a The Rf values and spectrophotometric prop- tannin which produced cyanidin, an anthocya- erties of these pigments were examined indi- nidin having two hydroxyl groups on the B vidually and the results were compared in ring, released the thioether of catechin upon Table 1 with the data on anthocyanidins by toluene-a-thiol treatment. Similarly, other Harborne (3). The Table revealed the follow- which produced , an anthocyanidin ing; Q-l, L-1 and B-2 were cyanidin, and having three hydroxyl groups on the B ring, C-2 and B-3 were delphinidin. In addition, released the thioether of gallocatechin upon B-1 appeared to be pelargonidin and C-1 was the same treatment. Table 2 indicates two a cyanidin-like compound. Since both pig- interesting conclusions; i) among the five ments were very minor components, a definite condensed tannins, only the two tannins pre- identification was difficult in the present exper- pared from carob bean and persimmon con- iment. tained gallate esters, ii) the ratio of catechin Each condensed tannin was heated in 0.1 or to gallocatechin varies considerably among the 0.2 N HCl for 40 min in a boiling bath. No three condensed tannins. or fewer polyphenolic spots were detected in Molecular weight estimation of methylated the EtOAc soluble fraction of the acidic solu- condensed tannins tion and identification of flavan-3-ols composed There has been no precise data on the molec- of condensed tannin was not successful here. ular weight and its distribution in condensed Toluene-a-thiol degradation of condensed tannins or proanthocyanidin polymers. Gel tannins filtration of Sephadex G-25 or 50 in 50% The degradation of kaki-tannin by toluene- aqueous methanol or acetone described in some a-thiol in ethanolic acetic acid resulted in the reports (2, 12, 15, 16) was unsuccessf tzl for formation of four polyphenolic compounds. examining the molecular weight of kaki-tannin They had already been identified as the thio- since it was adsorbed tightly to the gel. ethers of catechin, catechin-3-gallate, gallo- We succeeded in performing gel permeation catechin and gallocatechin-3-gallate (8) . Tan- chromatography of methylated kaki-tann in, in nins prepared from banana, carob bean, Chi- which phenolic hydroxyl groups was masked, nese quince and loquat also released degraded The methylated tannin prepared by the modi- products with toluene-a-thiol treatment. The fied Hakomori's method was estimated to be degraded products thus obtained from each ca. 1. 4X104 in Mw and ca. 0. 6x104 in Mi condensed tannin were compared with four (8). By the same method, three cond ensed products from kaki-tannin and identified chro- tannins, from banana, carob bean and Chinese matographically. Their quantitative ratio quince, were methylated and analyzed by gel were calculated by estimating the spot surface permeation chromatography in THF. areas after coloration of the polyphenolic spots Fig. 1 shows the typical chromatogram of with a vanillin-hydrochloric acid reagent on methylated tannins obtained from carob bean chromatograms. The results are summarized and Chinese quince. It revealed that meth- in Table 2 and Table 3. It was found that ylated carob bean tannin was similar t o the banana-tannin consists of catechin and gallo- methylated Chinese quince tannin in molecular catechin with the ratio of about 1 to 1. 3, size. Mw and Mn of both methyl ethers were Chinese quince- and loquat-tannin consists of 1.27 X 104 and 0.26 X 104, 1.44 X 104 and . 20x only catechin, and carob bean-tannin consists 104, respectively. Each tannin was methylated of catechin-3-gallate, gallocatechin and gallo- twice or three times using the modified Hako- 266 JOURNAL OF THE JAPANESE SOCIETY FOR HORTICULTURAL SCIENCE

materials present in the leaves, fruit and flowers of many higher has long been known, and the colour was later shown to be that of the pigment anthocyanidin, mostly cyanidin and delphinidin. Rosenheim in 1920 (13) reported the first systematic investigation of these substances for which he proposed the term leucoanthocyanin. Weinges (1969) reclas- sified the colourless compounds isolated from plant tissues and reserved the term leucoantho- Fig. 1. Gel permeation chromatography of two for compounds such as the flavan- methylated tannins 3, 4-diols which occur in and heartwood Both tannins, from young fruits of Chinese quince and carob bean, were methylated once by the modified of trees, and the name condensed proanthoc- Hakomori's method. HPLC was carried out with the yanidin for the various flavan-3-ol dimers, following conditions ; column, TSK-gel 5, 4, 3,2 H 6, trimers and higher oligomers found in plants, 7.5 x 600mm, mobile phase, tetrahydrofuran, detection, especially, fruit, leaves and (21). There- transmittance (%) at 280nm, flow rate, 1.Oml f min. ---; methylated Chinese quince-tannin, ; after, there have been many reports on the methylated carob bean-tannin. chemical investigation of proanthocyanidin, mainly dimers and trimers (5, 6, 7). mori's method, in order to narrow the molec- Thompson et al. (19) reported in detail, that ular weight distribution of individual samples. toluene-a-thiol was an excellent reagent for The results of HPLC analysis are shown in examining the structure of procyanidin B Fig. 2. Four methylated preparations showed groups because it cleaved trimeric and dimeric abnormal chromatograms, which were recog- at their carbon-carbon linkages nized by two shoulder peaks (at about 50 and and freed flavan-3-ol from the lower unit and 53 counts) and the presence of low molecular the thiol derivative from the upper unit were weight components, probably degraded prod- released with high yield in acidic ethanol. ucts. Excess exposure to alkali, NaH and In the present paper, polyphenolic polymers methylsulfinyl carboanions, may degrade tannin prepared from five different fruits can be polymers to low molecular weight components classified as condensed tannins by considering thereby causing the abnormal chromatograms. the following properties : precipitation of gela- tin, insolubility in ethyl acetate, astringent Discussion taste and the formation of deep red pigments The formation of red colours from colourless as well as amorphous with acids.

Fig. 2. Gel permeation chromatography of four methylated tannins Four kinds of condensed tannins were methylated twice or three times by the modified Hakomori's method. HPLC was carried out in the same conditions as Fig. 1. --- ; persimmon , ; carob bean, o ; banana, - - ; Chinese quince. MATSUOAND IT00 : STUDIESOF CONDE NSED TANNINSFROM YOUNG FRUITS 267

Our findings indicate that they are polymeric of pelargonidin from carob bean tannins but because they precipitated in did not identify a Fcorresponding flavan-3-ol, methanol with the addition of K2HPO4i on of zelechin. We also found that banana-tannin acid treatment gave rise to a deep red colour, produced a pelargonidin-like substance (Table and released the thioethers of flavan-3-ols with 1). If such rare flavan-3-ol, having mono- toluene-cr-thiol treatment in acidic ethanol. hydroxylated B ring, is present in some fruit This evidence gives support to the conclusion tannins, it is very interesting in respect of that some or most of condensed tannins must plant tannin biosynthesis. be recognized chemically to be proanthocya- Estimating precisely the molecular weight nidin polymers. We agree with the opinion of proanthocyanidin polymers is known to be that such tannins should be called flavanan or very difficult due to their chemical and physical flavolan tannins, instead of condensed tannin properties, for example, lability to heat, acids (1, 11, 14). and alkalis, and a strong tendency to form It is interesting that five different plant hydrogen and hydrophobic bonds. We succeed- species which are taxonomically diverse contain ed previously in estimation the molecular tannins having common chemical structures, weight of methylated kaki-tannin by gel per- a proanthocyanidin polymer or flavanan tan- meation chromatography (8). Kaki-tannin nin. From a plant physiological standpoint, was observed as a single and obtuse peak in however, the hydroxylation pattern of flavan- the chromatogram and was calculated to be 3-ols and the presence of gallate esters appear ca. 1.4 X 104 in Mw and ca. 0.6 X 104 in Mn to be related to the relative taxonomic position (8). However, Fig. 2 and Table 4 showed of each species. that the methylated samples of tannins from Tamir et al. (18) had examined tannins iso- the other fruits have one or two peaks and lated from ripe carob bean pods by the use of some low molecular weight components. thioglycolic acid degradation and acid hydro- These abnormal chromatograms may be arti- lysis techniques. They concluded that the facts formed by excess alkali treatment or polymeric tannins consisted of (-)-epigallo- relatively high room temperature of methy- catechin, (-)-epigallocatechin gallate and (-)- lation processes (at about 26°C). This view is epicatechin gallate. Their findings are consis- supported by the production of low molecular tent with our results shown in Table 3, which weight components and large ratio of Mw/Mn. were obtained with investigating tannins pre- Mw and Mn of only major and higher mole- pared from young, completely green pods. cular weight component which appeared to be Tamir et al. (18) observed also the production more intact tannin species were re-calculated

Table 4. Estimation of average molecular w ht of methy latedg tannins from Fig.l ei and 2 268 JOURNAL OF THE JAPANESE SOCIETY FOR HORTICULTURAL SCIENCE to be 1.24 X 104 and 0.76 X 104 and listed in pman and Hall Press, London. Table 4. These results are similar to the 5. HASLAM,E. 1977. Symmetry and promiscuity previous data. Finally, judging from the in procyanidin biochemistry. Phytochemistry above described aspects, the three methylated 16 : 1625-1640. tannins prepared from Chinese quince, banana 6. HASLAM, E. 1977. Structure, conformation and biosynthesis of natural procyanidins. pp. and carob bean, have similar molecular 97-110. In L. FARKAS, M. GABOR and F. weights, ca. 1.4--1.0 X 104 in Mw and ca. 0.7 -0 KALLAY (eds.), and bioflavonoids .3x104 in Mn. Methylated kaki-tannin is current research trends. Elsevier Scientific thought to be a slightly higher polymer than Pub. Com., Amsterdam-Oxford-N. Y. the other three methylated tannins. More 7. HASLAM, E. 1979. Vegetable tannins. pp. 475 precise data on molecular weights of tannins -523 . In T. SWAIN,J. B. HARBORNEand C. G. may be obtained from samples prepared under VAN SUMERE(eds.), Biochemistry of plant mild methylation, particularly at low temper- phenolics. Plenum Press, N. Y. and London. ature. 8. MATSUO,T. and S. IT00. 1978. The chemical Although all of four tannins except loquat- structure of kaki-tannin from immature fruit tannin examined in this experiment showed of the persimmon (Diospyros kaki L.). Agric. Biol. Chem. 42:1637-1643. almost similar polymerization degrees, flavan- 9. MATSUO,T. and S. IT00. 1981. A simple and 3-ols which constituted them were recognized rapid purification method of condensed tan- to be diverse in kind and quantitative ratio. nins from several young fruits. Agric. Biol. It is very interesting on the standpoint of Chem., in press. tannin biosynthesis. Further examination is 10. NAKABAYASHI,T. 1972. Tannin. pp. 64-115. in progress to investigate the relationships the In T. NAKABAYASHI,S. KIMURA and H. KATO intensity of astringency and chemical struc- (eds.), Shokuhin no Henshoku to Sonoka- tures of several condensed tannins. gaku (Discoloration of foods and its chemical consideration). Kourinshoin Press, Tokyo. Acknowledgements 11. PANKHURST,C. E., A. S. CRAIGand W. T. JONES. 1979. Effectiveness of Lotus root nodules I. The authors wish to thank Mitsubishi Chem- morphology and flavolan content of nodules ical Industrial LTD. for HPLC analysis, formed on Lotus peduculatus by fast-growing Mr. K. Y. Ogawa (California) for generous Lotus rhizobia. J. Expl. Bot. 30 : 1085-1093. supply of carob bean and Dr. S. J. Kays(Depart- 12. PORTER, L. J. and R. D. Wilson. 1972. The ment of Horticulture, The University of separation of condensed tannins on Sephadex Georgia) for valuable suggestions during the G-25 eluted with 50% aqueous acetone. J. preparation of the manuscript. This work Chromatogr. 71 : 570-572. was supported in part by grants from Mishima 13. ROSENHEIM,0. 1920. Observations on antho- cyanins. I. The of the young Kaiun Commorative Foundation. leaves of the vine. Biochem. J. 14 Literature Cited 178-188. 14. SARKAR,S. K., R. E. HOWARTHand B. P. GOPLEN. 1. CREASY,L. L. and D. T. SWAIN.1965. Structure 1976. Condensed tannins in Herbaceous legu- of condensed tannin. Nature 208: 151-153. mes. Crop Science 16 : 543-546. 2. DURKEE,A. B. and J. D. JONES.1969. A mild 15. SOMERS,T. C. 1966. Wine tannins-isolation of procedure for the extraction and fractionation condensed pigments by gel-filtra- of , proanthocyanin and other tion. Nature 209 : 368-370. of apple peel. Phytochemistry 16. STRUMEYER, D. H. and M. J. MALIN. 1975. 8 : 909-911. Condensed tannins in grain sorghum : isola- 3. HARBORNE,J. B. 1967. The anthocyanin pig- tion, fractionation, and characterization. J. ments II. pp. 1-36. In J. B. HARBORNE(ed), Agric. Food Chem. 23: 909-914. Comparative biochemistry of the flavonoids. 17. SWAIN, T. 1965. The tannins. pp. 552-580. Academic Press, N. Y. and London. In J. BONNERand J. E. VARNER (eds.), Plant 4. HASLAM,E. 1975. Natural proanthocyanidins. biochemistry. Academic Press, N. Y. and pp. 505-559. 1 n J. B. HARBORNE,T. J. MABRY London. and H. MABRY(eds.), The Flavonoids. Cha- 18. TAMIR, M., E. NACHTOMIand E. ALUMOT.1971. MATSUO AND ITOO : STUDIES OF CONDENSED TANNINS FROM YOUNG FRUITS 269

Degradation of tannins from carob pods istry of fruits and their product, Vol. II. (Ceratonia siliqua L.) by thioglycollic acid. Academic Press, N. Y. and London. Phytochemistry 10 : 2769-2774. 21. WEINGES, K., W. BAHR, W. EBERT, K. GoRITZ 19. THOMPSON,R. S., D. JACQUES,E. HASLAM and and H. D. MARX. 1969. Konstitution, Entste- R. J. N. TANNER. 1972. Plant proanthocyan- hung and Bedeutung der Flavonoidgerbstoffe. idins. part I. introduction ; the isolation, Fortschr. Chem. org. Naturst. 27: 158-260. structure, and distribution in nature of plant 22. WILKINS, C. K. 1973. Chromatography of tea procyanidins. J. Chem. Soc., Ser. III. 14 : 41 polyphenols on Sephadex columns as a -44 . method of estimation of molecular size. J. 20. VAN BUREN. J. 1971. pp. 269-304. Fruit Chromatogr. 87: 250-253. phenolics. In A. C. HULME(ed.), The biochem-

数種類の幼果 に含 まれ る縮合型 タソニソの化学的比較 研究

松 尾 友 明 ・伊 藤 三 郎 (鹿児島大学農学部)

摘 要

4種 類 の 強 い 渋 味 を有 す る幼 果(カ キ ・バ ナ ナ ・カ リ 加 に よ っ て 沈 殿 し な か っ た.こ の 物 質 は プ ロ ア ン トシ ア ソ ・キ ャ ロ ブ豆)よ り渋 味 成 分 で あ る タ ン ニ ン物 質 を 抽 ニ ジ ン オ リ ゴ マ ー で あ る こ とが 推 測 さ れ た.

出,精 製 し,そ の化 学 構 造 を比 較,検 討 した. ゲ ル パ ー ミエ イ シ ョ ン ク ロ マ ト グ ラ フ ィー の 結 果 か そ れ ぞ れ の タ ン ニ ソ物 質 は縮 合 型 タ ン ニ ンの 一 般 的 な ら,バ ナ ナ ・カ リ ン ・キ ャ ロ ブ 豆 の タ ン ニ ン の メ チ ル 化 性 質 と と もに 次 の よ うな特 異 な性 質 を 示 した. 物 は カ キ タ ン ニ ン の メ チ ル 化 物 よ り や や 低 分 子 で あ る 1.メ タ ノー ル溶 液 か ら リ ン酸 ニ カ リウ ムの 添 加 に よ が,た が い に 近 似 し た 分 子 量 を 持 つ こ と が 示 さ れ た(Mn =1.4-1 り白沈 した. .OX104,Mn=O.7-0.2×104). ワ 臼 酸 処 理 に よ りア ン ト シ ア ニ ジ ンを 生 成 し た. 酸 と トル エ ンーα 一チ オ ー ル 処 理 に よ る 分 解 生 成 物 の 同 つ り トル エ ンーα 一チ オ ー ル 処 理 に よ り高 収 率 で 分 解 さ 定 か ら各 タ ソ ニ ン の 構 成 成 分 は 以 下 の よ う に 推 定 さ れ

れ,フ ラ バ ソ ー3一オ ー ル の チ オ エ ー テ ル を 生 成 し た.カ キ タ ン ニ ン が カ テ キ ン ・カ テ キ ン ー3一ガ レ ー ト・ガ

た. ロ カ テ キ ン ・ガ ロ カ テ キ ン ー3一ガ レー ト(1:1.2:2.1:

これ らの知 見 は, こ の4種 類 の タ ン ニ ン 物 質 が プ ロ ア 2.2,各 成 分 の 量 比)か ら構 成 さ れ て い る の に 比 べ て,バ トシア ニ ジ ン,ポ リマ ーの 共 通 な 化 学 構 造 を 持 つ こ とを ナ ナ の タ ン ニ ン は カ テ キ ン と ガ ロ カ テ キ ン(1:1.3),キ 示 唆 して お り,そ れ ゆ え,縮 合 型 タ ソ ニ ンで は な く,フ ャ ロ ブ 豆 の タ ン ニ ン は カ テ キ ン ー3一ガ レ ー ト ・ガ ロ カ テ ラバ ナ ン(あ るい は,フ ラ ボ ナ ン)タ ン ニ ンが 適 切 な 名 キ ン ・ガ ロ カ テ キ ン ー3一ガ レ ー ト(1:3.3:4.6)か ら 成 称 で あ る こ とを 提唱 した. り,カ リ ン と ビ ワ の タ ン ニ ン で は カ テ キ ソ の み か ら 構 成 比 較 的 渋味 の な い ビ ワの幼 果 に 含 まれ る タ ン ニ ン物 質 さ れ て い る こ と が 明 ら か と な っ た. は 類 似 の化 学 的 性 質 を示 した が,リ ン酸 ニ カ リウム の添