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Two new phenolic compounds, teadenol A (1) and teadenol B (2), were isolated from tea (Camellia sinensis L.) leaves fermented with Aspergillus sp. (PK-1, FARM AP-21280). The chemical structures of 1 and 2 were elucidated based on the analyses of their spectroscopic data. The absolute configurations of the structures of 1 and 2 were also certified by their biosynthetic preparation in the treatment of tea catechins with Aspergillus sp.

Two new iridoid diesters of glucopyranose were isolated from the aerial part of Linaria canadensis (L.) Dum. Eight known flavones, apigenin, diosmetin, genkwanin, luteolin, luteolin 7-O-glucoside, luteolin 7-O-glucuronide, genkwanin 4'-O-rutinoside, and quercetin 7-O-rutinoside were also isolated. The chemical structures of the isolated compounds were elucidated based on the analyses of the spectroscopic data.

Chromatographic separation of black tea polyphenols is too difficult to supply sufficient quantities of pure compounds for biological experiments. Thus, facile methods to prepare black tea constituents were desired. Treatment of epigallocatechin gallate with copper(II) chloride efficiently afforded an unstable quinone dimer, dehydrotheasinensin A, and subsequent treatment with ascorbic acid stereoselectively yielded theasinensin A. The latter is a dimer with an R-biphenyl bond, one of the major polyphenols found in black tea. The method is simpler and more effective than enzymatic preparation.

Two new diketopiperazine derivatives, bacillusamides A (1) and B (2), have been isolated from the EtOAc extract of the sea urchin-derived Bacillus sp. along with the known cyclo(-L-pro-L-val-) (3), cyclo(-L-pro-L-tyr-) (4), cyclo(-L-pro-L-phe-) (5). These structures were elucidated by extensive spectroscopic methods. Furthermore, the absolute configurations of the amino acid residues were determined using Marfey's method. Compound 1 displayed weak antifungal activity against Aspergillus niger.

This review will discuss recent progress in the chemistry of secondary polyphenols produced during food processing. The production mechanism of the secondary polyphenols in black tea, whisky, cinnamon, and persimmon fruits will be introduced. In the process of black tea production, tea leaf catechins are enzymatically oxidized to yield a complex mixture of oxidation products, including theaflavins and thearubigins. Despite the importance of the beverage, most of the chemical constituents have not yet been confirmed due to the complexity of the mixture. However, the reaction mechanisms at the initial stages of catechin oxidation are explained by simple quinone-phenol coupling reactions. In vitro model experiments indicated the presence of interesting regio- and stereoselective reactions. Recent results on the reaction mechanisms will be introduced. During the aging of whisky in oak wood barrels, ellagitannins originating from oak wood are oxidized and react with ethanol to give characteristic secondary ellagitannins. The major part of the cinnamon procyanidins is polymerized by copolymerization with cinnamaldehyde. In addition, anthocyanidin structural units are generated in the polymer molecules by oxidation which accounts for the reddish coloration of the cinnamon extract. This reaction is related to the insolubilization of proanthocyanidins in persimmon fruits by condensation with acetaldehyde. In addition to oxidation, the reaction of polyphenols with aldehydes may be important in food processing.

Hydrophobic catechin derivatives were produced by heating with natural aldehydes or allyl alcohols. (+)-Catechin or (-)-epigallocatechin-3-O-gallate was heated with trans-2-hexenal, citral, (+)-citronellal, geraniol, or phytol. Although each reaction generated complex mixtures of products, 11 compounds were isolated and characterized by spectroscopic methods. The unsaturated aldehydes were found to attach to the flavan A-ring. Besides C-C linkage between aldehyde and the C-8 and/or C-6 of the catechin A-ring, formation of ether linkages between unsaturated carbons of the aldehydes and phenolic hydroxyl groups was observed. The allyl alcohols, geraniol and phytols, reacted at the galloyl group as well as the A-ring. After partitioning between triglyceride and water, the lipid layer of the reaction products showed strong 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity. In contrast, epigallocatechin-3-O-gallate was not transferred to the lipid layer.

In a project to produce a new fermented tea product from non-used tea leaves harvested in the summer, we found that kneading tea leaves ( Camellia sinensis ) with fresh loquat leaves ( Eriobotrya japonica ) accelerated the enzymatic oxidation of tea catechins. The fermented tea obtained by tea-rolling processing of tea and loquat leaves had a strong, distinctive flavor and a plain aftertaste, which differed from usual black, green, and oolong teas. The phenolic constituents were similar to those of black tea. However, the concentrations of theaflavin 3-O-gallate, theaflavin 3,3'-di-O-gallate, and thearubigins were higher in the tea leaves kneaded with loquat leaves than in tea leaves kneaded without loquat leaves. The results from in vitro experiments suggested that acceleration of catechin oxidation was caused by the strong oxidation activity of loquat leaf enzymes and a coupled oxidation mechanism with caffeoyl quinic acids, which are the major phenolic constituents of loquat leaves.

Four new dammarane-type triterpene saponins named floranotoginsenosides A (1), B (2), C (3) and D (4), together with five known triterpene saponins, were isolated from the flowers of Panax notoginseng. Their structures were elucidated on the basis of spectral and chemical evidence.

A new ellagitannin dimer named euscaphinin was isolated from the leaves of Euscaphis japonica (THUNB.) KANITZ. The structure of this dimer was determined on the basis of spectroscopic and chemical evidence. The resulting structure indicated that it was produced by intermolecular C-O oxidative coupling between the galloyl groups of molecules of 1(beta)-O-galloyl pedunculagin, the major ellagitannin of the leaves. The ellagitannins were not detected in the bark and wood part of the plant. This is the first example of the isolation of ellagitannins from Staphyleaceaeous plants.

Three new phenolic compounds named whiskey tannins A and B and carboxyl ellagic acid were isolated from commercial Japanese whiskey, along with gallic acid, ellagic acid, brevifolin carboxylic acid, three galloyl glucoses, a galloyl ester of phenolic glucoside, 2,3-(S)-hexahydroxydiphenoylglucose, and castacrenin B. Whiskey tannins A and B were oxidation products of a major oak wood ellagitannin, castalagin, in which the pyrogallol ring at the glucose C-1 position of castalagin was oxidized to a cyclopentenone moiety. These tannins originated from ellagitannins contained in the oak wood used for barrel production; however, the original oak wood ellagitannins were not detected in the whiskey. To examine whether the whiskey tannins were produced during the charring process of barrel production, pyrolysis products of castalagin were investigated. Dehydrocastalagin and a new phenolcarboxylic acid trislactone having an isocoumarin structure were isolated, along with castacrenin F and ellagic acid. However, whiskey tannins were not detected in the products.

Structures of two condensation products obtained by the reaction of cinnamaldehyde with (+)-catechin were determined by spectroscopic methods. One had two phenylpropanoid units at the C-6 and C-8 positions of the catechin skeleton. The other product had a dimeric structure with two catechin and two phenylpropanoid units. Matrix-assisted laser desorption time-of-flight mass spectrometric analysis of the reaction products of cinnamaldehyde with procyanidin B1 suggested that procyanidins were oligomerized in a manner similar to the reaction with catechin. Furthermore, (13)C NMR spectral comparison of the condensation products with the polymeric procyanidins obtained from commercial cinnamon bark strongly suggested that the procyanidins in the cinnamon bark also were polymerized by reaction with cinnamaldehyde.

Four hydrolyzable tannins named balanophotannins D-G ( 1- 4) were isolated from the aerial parts of the parasitic plant Balanophora japonica. Their structures were characterized on the basis of spectroscopic and chemical evidence. Balanophotannins D-G contain an oxidized hexahydroxydiphenoyl (HHDP) group. The absolute configurations of balanophotannins D ( 1) and F ( 3) were determined via the PGME method. Balanophotannin E ( 2) showed cytotoxicity to Hep G2 cancer cells with an IC 50 value of 4.22 microM.

Two new bicyclic polyketide lactones, polyrhacitides A ( 1) and B ( 2), were isolated from Chinese medicinal ants, Polyrhacis lamellidens, which have been used as an effective therapeutic agent to treat rheumatoid arthritis and hepatitis in China. Their absolute structures were elucidated on the basis of spectroscopic analyses and chemical evidence. The occurrence of polyketides with similar structures in plants of the Lamiaceae, Lauraceae, and Staphyleaceae indicates their significance in the study of chemical ecology.

Lipase and amylase inhibitory activities of black tea were examined. After solvent partitioning of a black tea extract with the ethyl acetate and n-butanol, the two soluble fractions showed comparable inhibitory activities. Activity in the ethyl acetate fraction was mainly attributable to polyphenols with low-molecular weights, such as theaflavin gallates. On the other hand, the active substance in the n-butanol layer was ascertained to be a polymer-like substance. 1H- and 13C-NMR spectra showed signals arising from the flavan A-ring and galloyl groups, although signals due to flavan B-rings were not detected, suggesting that the polymer-like substances were generated by oxidative condensation of flavan B-rings, a result which was previously deduced from our results of in vitro catechin oxidation experiments. Enzymatic oxidation of epicatechin 3-O-gallate produced a similar polymer-like substance and suggested that condensation between a B-ring and galloyl groups was involved in the polymerization reaction.

The antitrypanosomal activity of methanolic extracts of Anogeissus leiocarpus and Terminalia avicennoides were evaluated in vitro against four strains of Trypanosoma species with minimum inhibitory concentration (MIC) value range of 12.5-50 mg/ml. Successive fractionations of the two plant extracts in water, butanol and ethyl acetate gave a range of activity (MIC, 20 to > or =50 microg/ml). Activity-guided and chromatographic analysis of butanolic fractions on Sephadex LH-20 column followed by high-performance liquid chromatography, nuclear magnetic resonance analysis and both ultraviolet and thin layer chromatography revealed hydrolysable tannins with a range of activity (MIC, 7.5-27.5 microg/ml or 14-91 microM). Effect of the compounds on fibroblasts did not reveal serious toxicity at moderate concentration but is concentration dependent.

Two new maltol glycosides, maltol 6'-O-beta-D-apiofuranosyl-beta-D-glucopyranoside and maltol 6'-O-(5-O-p-coumaroyl)-beta-D-apiofuranosyl-beta-D-glucopyranoside, were isolated from Elsholtzia rugulosa Hemsl. along with 11 known compounds including prunasin and amygdalin. The structures were determined on the basis of spectroscopic and chemical evidence. This is the second example of isolation of cyanogenic glycosides from Lamiaceous plants.

During black tea production, catechins and their galloyl esters are enzymatically oxidized to generate a complex mixture of black tea polyphenols. The role of galloyl ester groups in this process has yet to be determined. Enzymatic oxidation of epicatechin 3-O-gallate (1) yielded two new oxidation products, theaflavate C and bistheaflavate A, along with theaflavate A (2), a known dimer of 1 generated by coupling of the B-ring with the galloyl group. Theaflavate C is a trimer of 1 and possesses two benzotropolone moieties generated by the oxidative coupling of the galloyl groups with the catechol B-rings. Bistheaflavate A was found to be a tetramer produced by intermolecular coupling of two benzotropolone moieties of 2. From the structures of the products, it was deduced that oxidative coupling of galloyl groups resulted in extension of the molecular size of the products in catechin oxidation.

Six new ellagitannins herein, rubusuaviins A-F, were isolated from the aqueous acetone extract of Chinese sweet tea (Tien-cha, dried leaves of Rubus suavissimus S. LEE) together with seven known tannins. Rubusuaviin A was characterized as 1-O-galloyl-2,3-O-(S)-HHDP-4,6-O-(S)-sanguisorboyl-beta-D-glucopyranose. Rubusuaviins B, C, and E are dimeric, trimeric, and tetrameric ellagitannins, respectively, in which the sanguisorboyl groups were connected ellagitannin units. Rubusuaviins D and F were desgalloyl derivatives of rubusuaviins C and E, respectively. The inhibition of alpha-amylase activity by rubusuaviins and related ellagitannins was compared. Ellagitannins with beta-galloyl groups at the glucose C-1 positions showed stronger inhibition compared with the alpha-galloyl and desgalloyl compounds. The molecular weight of these compounds was not important for the inhibition of alpha-amylase activity.

One-pot reactions of aldoses with L-cysteine methyl ester and o-tolyl isothiocyanate yielded methyl 2-(polyhydroxyalkyl)-3-(o-tolylthiocarbamoyl)-thiazolidine-4(R)-carboxylates. Direct HPLC analysis of the reaction mixture and UV detection at 250 nm discriminated D- and L-enantiomers of aldoses. The reaction was applied to the determination of absolute configuration the sugar residues of an aroma precursor.

In order to clarify the mechanism for formation of catechin oligomers during the fermentation stage of black tea manufacture, epigallocatechin-3-O-gallate, the most abundant tea flavanol in fresh tea leaves, was enzymatically oxidized and the resulting unstable quinone metabolites were converted to phenazine derivatives by treatment with o-phenylenediamine. In addition to formation of monomeric and dimeric derivatives, four trimeric derivatives were isolated whose structures were determined by application of spectroscopic methods. The derivatives differed from each other in the location of the phenazine moieties and in the atropisomerism of the biphenyl bond. The results suggested that oxidative coupling of the galloyl group with the B-ring proceeds by a quinone dimerization mechanism similar to that for production of theasinensins.

Reaction 6(A),6(B)-di(O-tosyl)-beta-cyclodextrin with Na(2)S in DMF gave the cis-dimer of beta-cyclodextrin in 21% isolated yield while the trans-dimer was not detected.

The relationship between the structure and antibacterial activity of 22 polyphenols was analyzed by using minimum inhibitory concentration (MIC) as a criterion against 26 species of bacteria which can grow in Mueller-Hinton medium. There was no clear correlation between Gram-staining and bacterial susceptibility to polyphenols, and the extent of the susceptibility was approximately dependent on the species of bacteria. In the same Gram-negative bacteria, the antibacterial activity of the polyphenols against Aeromonas hydrophila, Vibrio parahaemolyticus and Vibrio vulnificus was comparatively strong. On the other hand, the activity against 11 species of the Enterobacteriaceae was comparatively weak, and the activity against six species of aerobic bacteria causing plant disease was moderate. Polyphenols having pyrogallol groups showed strong antibacterial activity, and those with catechol and resorcinol rings showed lower activity. The structure-activity relationship was extended to 26 polyphenol-rich plant extracts which could have potent antibacterial activity suitable for commercial use.

A theaflavin-related benzotropolone pigment formed between procyanidin B-1 and (-)-epigallocatechin was synthesized enzymatically for the first time. The condensation occurred regioselectively at the extension (upper) unit of the procyanidin, probably due to a steric effect.

During tea fermentation, oxidation-reduction dismutation of a number of quinone metabolites of tea catechins yields numerous minor products, which make it difficult to separate and purify black tea polyphenols. In this study, epigallocatechin-3-O-gallate was enzymatically oxidized and then the unstable quinone metabolites in the oxidation mixture were hydrogenated with 2-mercaptoethanol to reduce production of inseparable minor dismutation products. As a result, three new oxidation products including a new black tea pigment were isolated, and their structures were determined based on chemical and spectroscopic data. Dehydrotheasinensin AQ is a new reddish-orange pigment with a 1,2-diketone structure, and its presence in commercial black tea was confirmed. In addition, a new quinone dimer with a complex caged structure and a trimer of epigallocatechin-3-O-gallate were also isolated and their production mechanisms are proposed. The presence of this trimer suggested participation of galloyl quinones in production of minor polyphenols in black tea.

Three new ellagitannins named balanophotannins A-C having a 1,1'-(3,3',4,4'-tetrahydroxy)dibenzofurandicarboxyl group in their molecules and four known lignan glycosides were isolated from the extracts of fresh aboveground and underground parts of a medicinal parasitic plant Balanophora japonica (Balanophoraceae). Their structures were elucidated on the basis of spectral and chemical evidence. Chemotaxonomic significance of the known lignan glycosides in Balanophora japonica was discussed.

The antibacterial activities of 10 different plant polyphenols were evaluated by comparing their minimum inhibitory concentrations (MICs) against several food-borne pathogenic bacteria, Staphylococcus aureus (20 strains), some serotypes of the genus Salmonella (26 strains), Escherichia coli (23 strains), and some species of the genus Vibrio (27 strains). The polyphenols examined were epigallocatechin (1), epigallocatechin-3-O-gallate (2), punicalagin (3), tannic acid (4), castalagin (5), prodelphinidin (6), geraniin (7), procyanidins (8), a theaflavin mixture of black tea (9), and green tea polyphenols treated with loquat polyphenol oxidase (10). The average MICs of all polyphenols against S. aureus and the genus Vibrio (192+/-91 and 162+/-165 microg/ml, respectively) were much lower than the values against the genus Salmonella and E. coli (795+/-590 and 1519+/-949 microg/ml, respectively) (p<0.01). The coefficient of variation of the MICs of all polyphenols against S. aureus was the least and that against the genus Vibrio was the greatest. The mean MICs of each plant polyphenol against S. aureus (98-389 microg/ml) and the genus Vibrio (68-488 microg/ml) were similar. The relatively lower mean MIC values of 1, 2, 5, and 6 suggest the importance of 3,4,5-trihydroxyphenyl groups in antibacterial activity.

It has previously been demonstrated that cork tissue increases the efficiency of the production of lipophilic secondary metabolites in diverse plant cell suspension cultures. In the present study, three new homoisoflavonoids--named dihydrobonducellin, 2'-methoxydihydrobonducellin, and 2'-methoxybonducellin--and bonducellin and isobonducellin were isolated from Caesalpinia pulcherrima cultured cells coincubated with cork tissue. Cork tissue increased the production of 2'-methoxybonducellin by about 7-fold relative to control cells, and more than 80% of the product was recoverable from the cork tissue. When cork tissue and methyl jasmonate or yeast extract were added simultaneously to the medium, the amount of 2'-methoxybonducellin produced increased further. The production of the other four homoisoflavonoids was enhanced by variable amounts. Our results indicate that the addition of cork tissue would be an effective technique for investigating formation of secondary metabolites that usually accumulate only in trace amounts., (Copyright 2004 Elsevier Ltd.)

Eighteen main compounds, including four norsesquiterpenoids (1-4) and 14 phenolic compounds (5-18) isolated previously from Phyllanthus emblica, together with a main constituent, proanthocyanidin polymers (19) identified at this time from the roots, were estimated for their antiproliferative activities against MK-1 (human gastric adenocarcinoma), HeLa (human uterine carcinoma), and B16F10 (murine melanoma) cells using an MTT method. All of the phenolic compounds including the major components 5-8 from the fruit juice, 8, 9, and 12 from the branches and leaves, and 19 from the roots showed stronger inhibition against B16F10 cell growth than against HeLa and MK-1 cell growth. Norsesquiterpenoid glycosides 3 and 4 from the roots exhibited significant antiproliferative activities, although their aglycon 1 and monoglucoside 2 showed no inhibitory activity against these tumor cells.

Four new dimeric ellagitannins, paeonianins A-D (2-5), were isolated from the fruits of Paeonia lactiflora, together with a new ellagitannin monomer, paeonianin E (1). Their structures were determined by spectroscopic methods. Paeonianins A-D (2-5) are positional isomers formed by condensation of pentagalloyl-beta-D-glucose (8) with 5-desgalloylstachyurin (6) or casuariin (7). Paeonianin E is a C-glycosidic ellagitannin having a gallic acid methyl ester moiety at the glucose C-1 position. This is the first report of the isolation of dimeric ellagitannins from a plant in the family Paeoniaceae.

Enzyme inhibitory activities of 14 iridoids previously obtained from two Malaysian medicinal plants, Saprosma scortechinii and Rothmannia macrophylla, were evaluated in vitro using soybean lipoxygenase and bovine testis hyaluronidase. Most of the iridoids, including asperulosidic acid, paederosidic acid, and an epimeric mixture of gardenogenins A and B, did not show any effect on the enzyme activities, except for the bis-iridoids, which inhibited the lipoxygenase activity with their IC(50) values of approximately 1.3 times that of a known inhibitor, fisetin. Structural modification of asperulosidic acid and paederosidic acid through enzymatic hydrolysis by beta-glucosidase resulted in their inhibition towards the enzyme activities, and these activities were enhanced by the presence of some amino acids (lysine, leucine or glutamic acid) or ammonium acetate. Mixtures of gardenogenins A and B; isomers of non-glucosidic iridoids, incubated with amino acid or ammonium acetate did not show any inhibitory effect on the enzyme activities during the 6 h incubation period, except for lysine where spontaneous reaction between the iridoids and amino acid resulted in the inhibition of lipoxygenase activity. The results from these biomimetic reactions suggested that the iridoid aglycons and the intermediates formed by these reactive species could inhibit the enzyme activities, and thus substantiate previous reports that the formation of iridoidal aglycons is a prerequisite for the iridoid glycosides to demonstrate some of the biological activities. In addition, the results also indicated that it is worthwhile to further explore these intermediates as potential anti-inflammatory agents.

Production and accumulation of catechin dimer quinones during tea fermentation were chemically confirmed for the first time by trapping as phenazine derivatives. Direct treatment of the fermented tea leaves with o-phenylenediamine yielded five phenazine derivatives (8-12) of o-quinones of an epigallocatechin dimer and its galloyl esters (13-16), in which two flavan units were linked at the B-rings through a C-C bond. Atrop isomerism of the biphenyl bonds was shown to be the R configuration, suggesting that the o-quinone dimers were generated by stereoselective coupling of monomeric quinones. The total concentration of the phenazine derivatives in the o-phenylenediamine-treated tea leaves was higher than that of theaflavins. In contrast, phenazine derivatives of monomeric quinones of epigallocatechin were not isolated. When the fermented tea leaves were heated, the quinone dimers were converted to theasinensins, which are constituents of black tea, suggesting that theasinensins are generated by reduction of the quinone dimers during the heating and drying steps in black tea manufacturing.

A further investigation of the leaves and stems of Saprosma scortechinii afforded 13 compounds, of which 10 are new compounds. These were elucidated as the bis-iridoid glucosides, saprosmosides G (1) and H (2), the iridoid glucoside, 6-O-epi-acetylscandoside (3), and the anthraquinones, 1-methoxy-3-hydroxy-2-carbomethoxy-9,10-anthraquinone (4), 1-methoxy-3-hydroxy-2-carbomethoxy-9,10-anthraquinone 3-O-beta-primeveroside (5), 1,3-dihydroxy-2-carbomethoxy-9,10-anthraquinone 3-O-beta-primeveroside (6), 1,3,6-trihydroxy-2-methoxymethyl-9,10-anthraquinone (7), 1-methoxy-3,6-dihydroxy-2-hydroxymethyl-9,10-anthraquinone (8), 1,3,6-trihydroxy-2-hydroxymethyl-9,10-anthraquinone 3-O-beta-primeveroside (9), and 3,6-dihydroxy-2-hydroxymethyl-9,10-anthraquinone (10). Structure assignments for all compounds were established by means of mass and NMR spectroscopies, chemical methods, and comparison with published data. The new anthraquinones were derivatives of munjistin and lucidin.

Two new acylated flavanone glycosides, (S)-eriodictyol 7-O-(6"-O-trans-p-coumaroyl)-beta-D-glucopyranoside (1) and (S)-eriodictyol 7-O-(6"-O-galloyl)-beta-D-glucopyranoside (2) were isolated from the leaves and branches of Phyllanthus emblica together with a new phenolic glycoside, 2-(2-methylbutyryl)phloroglucinol 1-O-(6"-O-beta-D-apiofuranosyl)-beta-D-glucopyranoside (3), as well as 22 known compounds. Their structures were determined by spectral and chemical methods.

Six new sulfur-containing bis-iridoid glucosides, saprosmosides A-F (1-6), were isolated from the leaves of Saprosma scortechinii. From the stems of this same plant, two new iridoid glucosides, 3,4-dihydro-3-methoxypaederoside (8) and 10-O-benzoyldeacetylasperulosidic acid (12), were isolated. Their structures were elucidated by means of chemical, NMR, and mass spectroscopic methods. Additionally, 11 known iridoid glucosides were isolated and characterized as deacetylasperuloside, asperuloside, paederoside (7), deacetylasperulosidic acid (9), scandoside, asperulosidic acid, 10-acetylscandoside, paederosidic acid (10), 6-epi-paederosidic acid (11), methylpaederosidate, and monotropein. The structures of the new bis-iridoid glucosides were formed by intermolecular esterification between the glucose and carboxyl groups of three monomeric iridoid glucosides (7, 9, and 10).

Oxidation products of (-)-epicatechin and (-)-epigallocatechin by treatment with homogenates of 62 plants belonging to 49 families were compared. Forty-six plants were capable of synthesizing theaflavin, a black tea pigment, regardless of whether they contained catechins. Loquat, Japanese pear, and blueberry had activities higher than that of fresh tea leaves after 5 h of treatment; furthermore, these plants oxidized theaflavin to theanaphthoquinone. An additional new metabolite, dehydrotheasinensin, was generated on treatment with fresh tea leaves, eggplant, and unripened Japanese orange. Evidence for the oxidation of epigallocatechin and theaflavin by electron transfer to epicatechin quinone was demonstrated in a time course study using bananas and trapping the quinone intermediates as glutathione conjugates.

The association of 10 different tannins and related polyphenols with gramicidin S, a cyclic peptide having a rigid beta-turn structure, has been examined using 1H-NMR spectroscopy. In the presence of pentagalloylglucose and epigallocatechin-3-O-gallate, the proton signals due to proline and the adjacent phenylalanine moieties selectively shifted to up field, suggesting a regioselective association with the beta-turn structure. The association was also supported by the observation of intermolecular nuclear Overhauser effects between epigallocatechin-3-O-gallate and the peptide. In contrast, ellagitannins, biogenetically derived from pentagalloylglucose, showed small and non-selective chemical shift changes, suggesting that interaction with these tannins is relatively weak. The hydrophobicity of the tannin molecules and the steric hindrance of the interaction site are thought to be important in the association.

Methanolic extracts of the leaves, stems, and roots of Phyllagathis rotundifolia collected in Malaysia yielded seven galloylated cyanogenic glucosides based on prunasin, with six of these being new compounds, prunasin 2',6'-di-O-gallate (3), prunasin 3',6'-di-O-gallate (4), prunasin 4',6'-di-O-gallate (5), prunasin 2',3',6'-tri-O-gallate (6), prunasin 3',4',6'-tri-O-gallate (7), and prunasin 2',3',4',6'-tetra-O-gallate (8). Also obtained was a new alkyl glycoside, oct-1-en-3-yl alpha-arabinofuranosyl-(1-->6)-beta-glucopyranoside (9). For compounds 3-8, the galloyl groups were individually linked to the sugar moieties via ester bonds. All new structures were established on the basis of NMR and MS spectroscopic studies. In addition, prunasin (1), gallic acid and its methyl ester, beta-glucogallin, 3,6-di-O-galloyl-D-glucose, 1,2,3,6-tetra-O-galloyl-beta-D-glucose, strictinin, 6-O-galloyl-2,3-O-(S)-hexahydroxydiphenoyl-D-glucose, praecoxin B, and pterocarinin C were isolated and identified. The isolation of 1 and its galloyl derivatives (3-8) from a Melastomataceous plant are described for the first time.

A new biflavanone (1) with a C-3/C-3" linkage, a new daphnane-type diterpene (2) acylated by an unsaturated fatty acid, and a new coumarin glycoside (3), along with six lignans, two phenylpropanoids, five flavonoids, two diterpenes, and three coumarins were isolated from the roots of Stellera chamaejasme L. (Thymelaeaceae). Elucidation of these secondary metabolites of S. chamaejasme L. supplied strong chemical verification of the close taxonomic relationships among the genera Stellera, Daphne, and Wikstroemia, all of which belong to the family Thymelaeaceae.