Takuo Okuda's research while affiliated with Okayama University and other places
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Publications (249)
The structure of a new acylated flavonol glycoside from the leaf extract of Euphorbiamaculata was characterized as quercetin 3-O-(2″,3″-di-O-galloyl)-β-D-glucopyranoside. Four new hydrolyzable tannins together with twelve known tannins were also isolated and their structures were established by spectral and chemical means as 1,2,6-tri-O-galloyl-α-D...
Three hydrolyzable tannins of new types, glochiins M1, M2 and C1, were isolated from dried leaves of Glochidion rubrum BLUME, and their structures were elucidated by spectral and chemical methods.
Camelliatannin D (1), a new complex tannin which inhibits Ca release from mouse calvaria, was isolated from the leaves and fruits of Camellia japonica L. (Theaceae). This tannin is the first example of complex tannin composed of a dimeric hydrolyzable tannin and a flavan-3-ol.
Two new complex tannins, camelliatannins F (3) and G (4), were isolated from the leaves of Camellia japonica L. (Theaceae), and their structures, each consisting of an epicatechin unit and a C-glucosidic ellagitannin moiety, were elucidated. A new dimeric hydrolyzable tannin, named camelliatannin H (5), was isolated from the fruits of this plant. C...
Recently found antitumor, antiperoxidation, antivirus, and other activities of tannins, which are largely dependent on the structure of each tannin, enhanced the need for precise analyses of tannins. Centrifugal partition chromatography, combined with gel-column chromatography, facilitated preparative separation of tannins. In addition to fabms and...
Three minor flavonoids, licofuranocoumarin, isotrifoliol and glisoflavanone, were isolated from licorice (underground part of Glycyrrhiza uralensis), and their structures with 3-arylcoumarin, coumestan and isoflavanone skeletons were respectively elucidated on the basis of spectroscopic data.
The phytoehemical study of hydrolyzable tannins, naturally occurring complex polyphenols, has been facilitated by recent developments in modern analytical and spectroscopic techniques. Among numerous tannins characterized during the last two decades, those classified as oligomeric ellagitannins have attracted widespread attention as to their divers...
The progressive oxidative transformations in the biogenesis of hydrolyzable tannins, gallotannin (I) --> ellagitannin (II) --> dehydro ellagitannin (III) --> transformed dehydroellagitannin (IV), conform in several aspects to the evolutionary routes in the subclasses of Dicotyledonae, particularly in the Rosidae.
Chemical investigation on polyphenol-rich fractions of Cowania mexicana and Coleogyne ramosissima (Rosaceae) which showed significant inhibitory effects on Epstein-Barr virus early antigen (EBV-EA) activation induced by 12-O-tetradecanoylphorbol-13-acetate (TPA), has led to the characterization of 10 compounds including C-glucosidic ellagitannin mo...
Three hydrolyzable tannins, nobotannins L, M and N, were isolated from the water-soluble portion of the leaf extract of Tibouchina semidecandra, and their trimeric structures were elucidated from spectral and chemical evidence. Nobotanins L and N exist as equilibrium mixtures of four anomers due to the presence of two unacylated anomeric centers.
Tannins and lignins are two major classes of polyphenolic compounds widely distributed in the plant kingdom. Tannins are largely classified into hydrolyzable and condensed tannins.1 Hydrolyzable tannins have structures in which a polyalcohol (mainly glucose) is esterified with polyphenolic carboxylic acids, such as galloyl, hexahydroxydiphenoyl (HH...
Polyphenols such as flavonoids and tannins in medicinal plants, foods, and beverages are attracting considerable attention in human health care because of their biologically multifunctional properties. These properties include antioxidant activity due to radical scavenging action and anti-HIV, antitumor activities, and inhibitory effects on various...
Recent phytochemical studies on tannins and related polyphenols in medicinal plants traditionally used in China, Japan, and other countries have led to the characterization of numerous hydrolyzable tannins with diverse structures and have enabled studies on biological activities of individual tannins of defined structure.1 The pharmacological prope...
A number of medicinal plants have been traditionally used for treatment of various ailments, and it has been suggested that tannin may be the active agent of many of them. Among the major activities of tannins found are antioxidant and radical scavenging activities.1,2 These are the basic activities underlying the action of tannin-rich medicinal pl...
Two new monomeric hydrolysable tannins, acalyphidins M1 and M2, together with fourteen known polyphenols were isolated from the leaves of Acalypha hispida, and characterized as 1-O-galloyl-3,6-(R)-hexahydroxydiphenoyl-4-O-brevifolincarboxyl-β-d-glucose, and an oxidative metabolite of geraniin, respectively, by spectroscopic and chemical methods. A...
Two new ellagitannin dimers, cuphiins D1 and D2, and six known compounds including oenothein B and woodfordin C have been isolated from the aerial part of Cuphea hyssopifolia (Lythraceae). Macrocyclic structures of the new tannins were elucidated based on chemical and spectral evidence.
Geraniin, C41H28O27.7H2O, is the main tannin from Geranium thunbergii Sieb. et Zucc., which is one of the most popular folk medicines and also an official antidiarrheic drug in Japan. Conventional X-ray diffract- ometer data at 295 K and synchrotron data at 293 and 120 K (at EMBL/DESY Hamburg with a MARRE- SEARCH imaging plate) were measured. The s...
Five flavan dimers which showed lipase-inhibiting effects were isolated from fruits of Cassia nomame (Leguminosae). Structures of two new compounds among them were determined to be (2S)-3′,4′,7-trihydroxyflavan-(4β → 8)-catechin and (2S)-3′,4′,7-trihydroxyflavan-(4α → 8)-catechin. Fouf flavan dimers structurally related to these two compounds were...
A new galloylated flavonol glycoside, astragalin 2″,6″-di-O-gallate (loropetalin D), together with two related flavonol glycosides was isolated from the leaves of Loropetalum chinense. The two related flavonol glycosides were characterized as astragalin 2″-O-gallate and astragalin 6″-O-gallate by chemical methods, 1H and 13C NMR spectral analysis....
The host-mediated anticancer activity, which is an anticarcinogenic activity found for polyphenols besides the inhibition of mutagenicity and tumor-promotion, is specific to some oligomeric hydrolyzable tannins. Agrimoniin, a dimer isolated from Agrimonia pilosa which is used as a herbal medicine and vegetable, was the first oligomer of this type....
Eugeniflorins D1 and D2 new hydrolysable tannin dimers, were isolated, together with four known polyphenols, from Eugenia uniflora leaves. Their macrocyclic structures were elucidated from spectral and chemical evidence.
A new hydrolysable tannin was isolated from dried fruits of Melaleuca leucadendron and characterized as , based on the chemical and spectral evidence. Nine known hydrolysable tannins, as well as known stilbene glycosides and triterpenes, were also isolated.
Three new dimeric hydrolysable tannins, oenotheins D, F and G, together with known tannins including the macrocyclic oligomers, oenotheins A and B, have been isolated from roots and stems of Oenothera laciniata. Their structures were elucidated on the basis of chemical and spectral evidence. Oenotheins D and F were macrocyclic dimers isomeric with...
The discoloration of shikonin (1) and beta-carotene (2), occurring during storage of their ethanol solutions in the presence of oxygen in an illuminated room, was remarkably suppressed by hydrolyzable tannins, such as geraniin (4) and tannic acid JP (3) in the solution. The inhibitory effect of tannins was enhanced by the coexistence of metallic io...
Twelve questions concerning tannin selected from questions raised by other workers on the author's research were picked up. The answers of each question are as follows. 1. What is tannin?--the differences between the old concept and the new definition of tannin. 2. Is tannic acid the same as tannin? 3. How could each tannin be analyzed as a pure co...
Recent advances in isolation and structure elucidation of several hundred of new polyphenolic compounds of the tannin class using new techniques (1) have altered the definition of a tannin, at least that of a hydrolyzable tannin. Thus the term tannin now includes all polyphenolic compounds of defined chemical structure as well as the whole group of...
Three new complex tannins, stachyuranins A (1), B (2) and C (3), were isolated from the leaves of Stachyurus praecox (Stachyuraceae), and their structures, each consisting of a catechin or gallocatechin residue and a monomeric hydrolyzable tannin moiety, were assigned. Structures 1 and 2 lack a C-C linkage between glucose C-1 and the aroyl group at...
Two new hydrolyzable tannins, nobotanins J and K, were isolated by a combination of column chromatography and centrifugal partition chromatography from the leaf extract of Heterocentron roseum, and shown to have trimeric and tetrameric structures composed of combinations of the common monomeric units, casuarictin and pterocarinin C, on the basis of...
Two new hydrolysable tannins, brediatins A and B, along with 11 known hydrolysable tannins, were isolated from the leaves of Bredia tuberculata and were characterized as 1-O-galloyl-2,3-O-(S)-hexahydroxydiphenoyl-4,6-O-(1′S)-dehydrohexahydroxydiphenoyl-β-d-glucose and as a dimer structurally related to nobotanin A, based on chemical and spectroscop...
Three new hydrolyzable tannins, euphormisins M1, M2, and M3, were isolated from Euphorbia humifusa WILLD., and respectively characterized as 1,3,6-tri-O-galloyl-4-O- brevifolincarboxyl-beta-D-glucose (19), an oxidative metabolite (23) of geraniin, and 1,3,6-tri-O-galloyl-alpha-D-glucose (18), by spectroscopic and chemical methods. A new ellagic aci...
Camellioferin A, a new dimeric ellagitannin, was isolated, together with 13 known tannins, including camellins A and B, from Camellia oleifera. The structure of the new tannin elucidated by spectroscopic methods.
A new acylated γ-pyrone glucoside was isolated from the leaf extract of Gordonia axillaris (Theaceae), and was characterized as 3-O-(6'-O-galloyl)-β-D-glucopyranosylmaltol (7) based on two-dimensional NMR experiments and other spectroscopic analyses. 5-O-(6'-O-Galloyl)-β-D-glucopyranosylgentisic acid (6), and two dimeric hydrolyzable tannins [camel...
Luteolin was isolated as a lipase inhibitor from Cassia mimosoides var. nomame. During an investigation on the inhibitory effects of the other related flavonoids on lipase, flavonols (kaempferol, myricetin and quercetin) exhibited activity comparable to that of luteolin, while their glycosides, flavanones and flavan-3-ols showed negligible activity...
Two novel ellagitannin trimers, hirtellins T2 (1) and T3 (25), besides previously reported hirtellin T1 (28), have been isolated from the leaves of Reaumuria hirtella JAUB. et SP. (Tamaricaceae). Hirtellin T2 has a 36-membered macro-ring structure (1) with three dehydrodigalloyl (m-GOG) units connecting monomers, while hirtellin T3 (25) possesses o...
A new hydrolyzable tannin dimer [hirtellin G (1)], a trimer [hirtellin T1 (5)] and a tetramer [hirtellin Q1 (6)] have been isolated from the 70% acetone extract of the leaves of Reaumuria hirtella JAUB. et SP. (Tamaricaceae). These tannins were characterized as oligomers composed of two, three or four molecules of tellimagrandin II which are simila...
Two new ellagitannin dimers, euphorbins G (20) and H (21), together with 12 known polyphenols, were isolated from the leaves of Euphorbia prostrata (E. chamaesyce). Their structures, having 1C4 and 4C1 glucopyranose cores in each molecule, were established by spectroscopic and chemical methods. These new dimers, and 13 known hydrolyzable tannins, a...
The inhibitory effects on poly(ADP-ribose) glycohydrolase purified from human placenta of three classes of chemically defined tannins; gallotannins, ellagitannins and condensed tannins, were examined in vitro. Oligomeric ellagitannins were found to be most potent inhibitors of poly(ADP-ribose) glycohydrolase, their potencies increasing with increas...
The effects of chalcones and flavanone isolated from licorice roots (Glycyrrhiza inflata Bat.) on human polymorphonuclear neutrophil (PMN) degranulation were investigated. Licochalcone A (2-methoxy-4,4′-dihydroxy-5-α,α-dimethylallylchalcone) and licochalcone B (2-methoxy 3,4,4′-trihydroxychalcone), at concentrations of 10−6M to 10−3M, inhibited cal...
Seven highly active inhibitors against carbonic anhydrase (CA, EC 4.2.1.1), punicalin (2), punicalagin (3), granatin B (5), gallagyldilactone (7), casuarinin (8), pedunculagin (9) and tellimagrandin I (10), and four weakly active inhibitors, gallic acid (1), granatin A (4), corilagin (6) and ellagic acid (11), were isolated from the pericarps of Pu...
The effects of six flavonoids isolated from Sinkiang Licorice roots (lichochalcones A and B, isoliquiritigenin, isoliquiritin, liquiritigenin and liquiritin) on arachidonate metabolism and aggregation in human platelets were studied. Licochalcones A and B at concentrations of 10−5M to 10−3M inhibited the formation of 12-hydroxy-5,8,10-heptadecatrie...
A new polyphenol, 1,3,5-tri-O-caffeoylquinic acid, accompanied by 3,5-di-O-caffeoylquinic acid, has been isolated from the fruit of Xanthium strumarium.
Forty-five ellagitannins and related compounds were intraperitoneally injected into mice once, 4 d before intraperitoneal inoculation of S-180 cells, and their antitumor activities were evaluated. When an antitumor-active tannin was defined as one producing a 70% increase or more in the mean life span of mice or one regressor out of six mice, twent...
Four new dimeric hydrolyzable tannins, hirtellins C, D, E and F, besides previously reported hirtellins A and B, have been isolated from the leaf extract of Reaumuria hirtella Jaub. et Sp. (Tamaricaceae). Macrocyclic structures, 1 and 12, having both dehydrodigalloyl (DHDG) and isodehydrodigalloyl (isoDHDG) groups as the connecting units between mo...
Tamarixinins B and C, two new dimeric hydrolysable tannins, have been isolated from the flower extract of Tamarix pakistanica. Spectral data and chemical correlation with the known tannins by Smiles rearrangement established their structures, in which the monomeric units are linked to each other by isodehydrodigalloyl group(s).
Three new oligomeric hydrolysable tannins, loropetalins A-C, were isolated from Loropetalum chinense and their structures elucidated by spectral and chemical methods. Eighteen known tannins and related polyphenols, including oligomeric hydrolysable tannins (camelliin B and rugosins D, E and G), were also isolated.
Two new polyphenol glucosides, rocymosins A and B, were isolated from Rosa cymosa and characterized as 3-O-(6′-O-galloyl)-β-d-gluco
Recently found polyphenols of new types which are widely distributed in the Dicotyledoneae of the Angiospermae, are reviewed. These oligomeric hydrolysable tannins are classified according to the linkage between monomers, into five types: (i) GOG (and GOGOG), (ii) DOG, (iii) GOD, (iv) D(OG)2 and (v) C-glucosidic type, where G = galloyl, O = oxygen...
The antitumor effect of oenothein B, a macrocyclic ellagitannin from Oenothera erythrosepala Bordas, on rodent tumors was studied. Oenothein B exhibited a strong antitumor activity against MM2 ascites tumors upon intraperitoneal administration to the mice before or after the tumor inoculation. The tannin also inhibited the growth of Meth-A solid ty...
Two new polyphenolic compounds, melitric acids A (2) and B (5), were isolated from the aboveground part of Melissa officinalis (Labiatae) and their structures, consisting of three caffeic acid units, were determined from chemical reactions and spectral data. Rosmarinic acid (1) was also isolated.
The structures of hydrolysable tannins, each existing as an equilibrium mixture due to tautomerization at the sugar core(s) or at the dehydrohexahydroxydiphenoyl group (five- and six-membered hemiacetal forms) in the molecule, were elucidated by NMR, employing 2D NMR techniques (COSY, NOESY, 1H13C long-range COSY, etc.), on derivatives which avoid...
A HPLC survey of leaves of 80 plants (62 species, 15 hybrids, one variety and two cytotypes) from 18 genera of four subfamilies of Rosaceae, using five oligomeric hydrolysable tannins, five monomeric hydrolysable tannins, and chlorogenic acid as reference compounds, showed that the oligomers can be used as chemotaxonomic markers for the family, viz...
Our research objective is to develop nontoxic cancer chemopreventive agents and to apply these agents in treating humans. We are identifying agents that inhibit the process of tumor promotion in two-stage carcinogenesis experiments on mouse skin.
We review (a) the inhibitory effect of penta-O-galloyl-beta-D-glucose (5GG) on tumor promotion by teleo...
Epidemiological evidence shows that green tea may be a factor in lowering cancer risk. We have investigated the possibility that (-)-epigallocatechin gallate (EGCG), a major polyphenol in green tea, might be an antimutagenic substance. In the Ames Salmonella test, EGCG suppressed the direct-acting mutagenicity of 3-hydroxyamino-1-methyl-5H-pyrido-[...
Among 87 chemically defined tannins and related compounds, several hydrolyzable tannins, but not condensed tannins or other lower molecular weight polyphenols, significantly inhibited both the cytopathic effect of human immunodeficiency virus (HIV) and the expression of HIV antigen in human lymphotropic virus type I (HTLV-1)-positive MT-4 cells. Th...
Starting with the isolation of a crystalline tannin (geraniin) of mild property from a popular herb medicine (Geranii herba), various polyphenolic compounds including those belonging to new classes of tannins (oligomeric hydrolyzable tannins, complex tannins, and other metabolites and condensates) have been isolated from various medicinal plants. N...
Three new hydrolyzable tannins, eucalbanins A (5), B (8) and C (11), have been isolated from the fruit extract of Eucalyptus alba Reinw., and their structures were elucidated on the basis of spectral data and chemical correlation with known tannins. Quercetin-3-O-α-L-arabinopyranoside, (+)-catechin, procyanidin B-7, and nine known hydrolyzable tann...
Besides previously reported hydrolyzable tannin oligomers (woodfordins A-D), a new hydrolyzable tannin monomer [isoschimawalin A (7)] and five oligomers (woodfordins E-I) have been isolated from the dried flowers of Woodfordia fruticosa (an Indonesian crude drug, Sidowaya), and their structures elucidated on the basis of spectra and chemical eviden...
Three new hydrolyzable tannin dimers, nobotanins G (6), H (12) and I (13), have been isolated from the leaves of Heterocentron roseum (Melastomataceae), and their structures were elucidated on the basis of chemical degradations and nuclear magnetic resonance spectral analyses. Nobotanin I (13) is a novel dimer possessing a depsidone-forming valoneo...
Malabathrins A (6), E (11) and F (14), new complex tannins consisting of a C-glucosidic ellagitannin and a flavan 3-ol, have been isolated from the leaves of melastoma malabathricum L., and their structures were determined by chemical and spectroscopic methods including two-dimensional nuclear magnetic resonance spectroscopy.
Five new hydrolyzable tannin dimers, roshenins A-E, and eight known tannins and related polyphenols [(+)-catechin, (-)-epicatechin, procyanidins B-3 and B-4, sanguisorbic acid dilactone, sanguiins H-2, H-6 and lambertianin A], have been isolated from the root of Rosa henryi BOUL. The structures of roshenins A-E (9-12, 19), which have a sanguisorboy...
The quantitative analysis of (-)-epigallocatechin gallate (EGCG) in tea (Camellia sinensis L.) was performed by high-performance liquid chromatography (HPLC) with a C-18 reversed-phase column. EGCG was then eluted within 20 min by using methanol-water-acetic acid (20:75:5 (v/v/v)) as an eluent. As an internal standard, tryptophan was used. The cont...
Four new hydrolyzable tannins (phyllanthusiins A-D), a new polyphenol of related structure (phyllanthusiin E), and eight known polyphenols have been isolated from the leaves of Phyllanthus flexuosus. On the basis of the spectroscopic methods including 1H-13C long-range two-dimensional nuclear magnetic resonance techniques, phyllanthusiins A (9), B...
The leaves of Liquidambar formosana (Hamamelidaceae), used as herbal medicines, contain a complex array of hydrolyzable tannins including dimers and trimers. The structures of the dimer isorugosin E (11) and the trimer isorugosin G (12) were defined for the first time. In addition, application of NMR and CD spectroscopic data permitted assignment o...
The 1H nmr spectroscopy provides a convenient method of assigning the orientation of the valoneoyl group in the oligomeric hydrolyzable tannins, which is the unit most frequently joining the monomeric constituents in the molecules. The behavior of oligomers upon partial degradation has been found to be dependent on the location of valoneoyl group o...
A novel type of arylsulfotransferase which was obtained from a human intestinal bacterium catalyzes the sulfation of polyphenols related to tannins. Isoamyl gallate and (-)-epigallocatechin gallate were found to be sulfated rapidly using p-nitrophenylsulfate as a donor substrate. In the case of isoamyl gallate, two sulfated products, 3-monosulfate...
Four new hydrolyzable tannins, coriariins G, H, I and J, were isolated from the leaf of Coriaria japonica (Coriariaceae). Structures 1, 2 and 3, having a sedoheptulose residue, were assigned for coriariins G, H and I, respectively. Structure 4, having a depsidone-forming dehydrodigalloyl group, was assigned for coriariin J, based on the chemical co...
A new hydrolyzable tannin, antidesmes A (4), was isolated along with carpinusin (1) and geraniin (2) from dried leaves of Antidesma pentandrum MERR, var. barbatum MERR., and its dimeric structure, composed of devidiin (3) and geraniin (2), has been elucidated by spectral and chemical methods.
Three new hydrolysable tannin oligomers, davuriciins D1, D2 and T1, along with a main tannin, agrimoniin, have been isolated from the root extract of Rosa davurica. Their structures in which monomeric constituents are linked through a valoneoyl group and/or dehydrodigalloyl group, have been elucidated based on spectral and chemical evidence.
Inhibitory effects of 18 condensed tannins and related compounds on reverse transcriptase from an RNA tumour virus were examined in the presence of poly(riboadenylic acid) oligo(deoxythymidylic acid) ((rA)n(dT)12–18) or poly(ribocytidylic acid) oligo(deoxyguanylic acid) ((rC)n(dG)12–18) as a template-primer. A potent inhibitory effect was found in...
This report discusses a novel type of arylsulfotransferase (AST) which was derived from human intestinal bacterium sulfated polyphenolic compounds when p-nitrophenyl sulfate (PNS) was taken as a donor substrate. (+)-Catechin, (+/-)-catechin, (-)-epicatechin and (-)-epicatechin gallate were better substrates than tyramine. (-)-Epigallocatechin and (...
The roots and/or rhizomes of Glychyrrhiza uralensis, G. glabra and G. inflata, and commercial licorice specimens from various regions or countries were analyzed by high-performance liquid chromatography (HPLC), and classified into three types based on their phenolic constituents. i) Type A: The roots and rhizomes of G. uralensis, commercial licoric...
Two new antitumor trimeric hydrolyzable tannins, woodfordin D (5) and oenothein A (13), were isolated from the dried flowers of Woodfordia fruticosa, and their macrocyclic structures, which have a novel constituent unit (woodfordinoyl group) connecting the monomers, have been elucidated on the basis of spectral and chemical evidence. Oenothein A (1...
Two new phenolic compounds, glicoricone (3) and licofuranone (4), were isolated from a species of licorice brought from the northwestern region of China, and their structures were assigned. Among the twelve licorice constituents examined for the inhibition of monoamine oxidase (MAO), six compounds, 3, 4, genistein (6), licopyranocoumarin (7), licoc...
Two new dimeric hydrolyzable tannins, isorugosin E and hirtellin B, have been respectively isolated from Liquidambar formosana (Hamamelidaceae) and Reaumuria hirtella (Tamaricaceae), and their structures 7 and 15, in which two monomers are linked through a trisgalloyl group (valoneoyl or hellinoyl group), have been elucidated based on high resoluti...
]Two new hydrolysable tannins, hippophaenins Aand B, along with two flavonoids, six hydrolysable tannins and four C-glycosidic ellagitannins, have been isolated from leaves of Hippophae rhamnoides. Two polyphenols were also isolated from its fruits.
Cell suspension cultures of Geranium thunbergii produced (+)-catechin, procyanidin B3, pentagalloylglucose, and phyllanthusiin D which is not found in the intact plant. Geraniin, the main tannin in the intact plant, was detected in the cells of a different strain of this culture.
Two new monomeric hydrolyzable tannins [remurins A (12) and B (13)] and a new dimer [hirtellin A (7)], have been isolated from Reaumuria hirtella JAUB. et Sp. (Tamaricaceae). Hirtellin A and an additional new dimeric hydrolyzable tannin, tamarixinin A (6), along with three known tannins including hirtellin B (5), have also been isolated from Tamari...
Two new ellagitannin monomers, heterophylliins A (12) and E (13), and three dimers, heterophylliins B (17), C (18) and D (19), were isolated from leaf extract of Corylus heterophylla (Betulaceae), and their structures were elucidated based on spectral and chemical evidence. Seven known tannins, 1, 2, 3, 6-tetra-O-galloyl-β-D-glucose, tellimagrandin...
Four new hydrolyzable tannins, methylvescalagin and nobotanins, A, D and F, along with eleven known polyphenolics, have been isolated from the leaves of Tibouchina semidecandra COGN. Based on spectral and chemical evidence, nobotanin D was characterized as 1, 6-di-O-galloyl-2, 3-O-(S)-hexahydroxydiphenoyl-β-D-glucose (16), and the structures of nob...
Two new hydrolyzable tannins, schimawalins A (10) and B (17), have been isolated from the dried flowers of Schima wallichii (DC) KORTH. (Theaceae), and their structures, having a dilactonized valoneoyl group in the molecule, were established based on spectral and chemical evidence. Eight known hydrolyzable tannins, including camelliin B (8), the ma...
Four new hydrolyzable tannins, praecoxins A, B, C and D, were isolated from leaves of Stachyurus praecox Sieb. et Zucc. (Stachyuraceae), and their structures were elucidated.
The structures of three new hydrolyzable tannin oligomers, nobotanins B (7), C (20) and E (21), which were isolated from the leaves of Tibouchina semidecandra COGN. (Melastomataceae), have been elucidated on the basis of spectral and chemical evidence. Nobotanin B is an isomer of a co-existing dimer, nobotanin F, and nobotanins C and E are trimers...
Two new dimeric hydrolyzable tannins named eumaculin A (1) and eusupinin A (2) have been isolated from Euphorbia maculata L. and Euphorbia supina RAFIN., and their structures elucidated. Twelve other polyphenolic compounds including five hydrolyzable tannins and five flavonol glycosides have also been isolated.
A new monomeric hydrolyzable tannin, tirucallin A (7), and two new dimers, tirucallin B (11) and euphorbin F (14), have been isolated, together with six known polyphenols including euphorbin A, from the stems of Euphorbia tirucalli L., and their structures were elucidated by spectral and chemical methods. Euphorbin F (14) possesses dehydrohexahydro...
Two new complex tannins, camelliatannins A (1) and B (2), were isolated from the leaves of Camellia japonica L. (Theaceae). The structures of these tannins, each consisting of a C-glucosidic ellagitannin and (-)-epicatechin (9), were established by means of chemical degradation, synthesis from casuariin (4) and 9, and rotating frame Overhauser enha...
The Ministry of Health and Welfare of Japan supports the research on cancer chemoprevention within the framework of cancer research programs, because the increasing interest in cancer chemoprevention has been remarkable. However, the research on cancer chemoprevention is quite new in Japan. Therefore, we started to search for non-toxic inhibitory c...
Two new compounds named cornuside and cornusiin G were isolated from fruits of Cornus officinalis. Their structures were respectively determined to be 7-O- galloylsecologanol and a dimeric hydrolysable tannin composed of tellimagrandin II and 1,2,3,6-tetra-O-galloyl-β-d-glucose.
Callus cultures of Heterocentron roseum, under illumination with fluorescent lamps, produced a large amount of casuarictin, an ellagitannin monomer. Nobotanin B, a dimeric ellagitannin, was also produced by the callus cultures. Illumination with light was required for both cell growth and ellagitannin production. Shoots which were redifferentiated...
Callus and suspension cultures of Cinnamomum cassia were found to produce a large amount of condensed tannin. ( − )-Epicatechin and procyanidins B2, B4 and C1 which are precursors of condensed tannin were isolated from callus cultures. Tannin production in callus cultures was stimulated by coconut milk or malt extract supplemented in the medium. In...