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Biomedical subjects

I Kouno

Publications and source records attributed to I Kouno.

At least 19 recordsLinked to original sources
PubMed2004

A new diglycosyl megastigmane from Carallia brachiata.

A new megastigmane diglycoside was isolated from the leaves of Carallia brachiata. The structure was determined by spectroscopic methods as 3-hydroxy-5,6-epoxy-beta-ionol -3-O-beta-apiofuranosyl-(1-->6)-beta-glucopyranoside (1). Additionally, 29 known compounds consisting of two megastigmanes, one 1,2-dithiolane derivative, seven aromatic compounds, five condensed tannins, 12 flavonoids, and two glyceroglycolipids were isolated and identified.

Cyclohexanones↗
PubMed2001

Two types of oxidative dimerization of the black tea polyphenol theaflavin.

Theaflavin and its galloyl esters are polyphenolic pigments of black tea. In the course of studies on the oxidation mechanism of tea polyphenols, two theaflavin oxidation products named bistheaflavins A and B were isolated, and their structures were elucidated on the basis of MS and NMR spectroscopic analyses. Treatment of a mixture of (-)-epicatechin and (-)-epigallocatechin with banana fruit homogenate yielded bistheaflavin A together with theaflavin and theanaphthoquinone. The symmetrical structure of bistheaflavin A suggested that this compound was formed by oxidative C [bond] C coupling of two theaflavin molecules. In contrast, theaflavin in phosphate buffer (pH 7.3) was gradually oxidized to give bistheaflavin B and theanaphthoquinone. Bistheaflavin B possesses a bicyclooctane skeleton probably formed by intermolecular cyclization between dehydrotheaflavin and dihydrotheanaphthoquinone.

Antioxidants↗
PubMed2001

New eudesmane sesquiterpenes from the root of Lindera strychnifolia.

Strychnistenolide (1) and its acetate 2 were isolated from the root of Lindera strychnifolia, along with a novel rearranged type of secoeudesmane, strychnilactone (3). Their structures were elucidated by extensive analysis of their NMR spectra, including 2D NMR techniques, together with an X-ray analysis for 3. Strychnistenolide exists as a single stereoisomer in CHCl(3), but in pyridine is epimerized.

China↗
PubMed2001

Iridoids from Rothmannia macrophylla.

A new iridoid glucoside with an ether linkage between C-3 and C-10 and a novel nonglycosidic iridoid with an ether linkage between C-3 and C-6 and a lactonic linkage at C-1, named macrophylloside (1) and macrophyllide (2), respectively, were isolated from the leaves of Rothmannia macrophylla, along with six known iridoids. Their structures were established by NMR and MS spectroscopies.

Ethers↗
PubMed2001

Novel sesquiterpenoids from the roots of Phyllanthus emblica.

Three novel bisabolane-type sesquiterpenoids, phyllaemblic acids B (1) and C (2) and phyllaemblicin D (3), together with two new phenolic glycosides, 2-carboxylmethylphenol 1-O-beta-D-glucopyranoside (4) and 2,6-dimethoxy-4-(2-hydroxyethyl)phenol 1-O-beta-D-glucopyranoside (5), were isolated from the roots of Phyllanthus emblica. The structures of 1-5 were established by spectral and chemical methods. The absolute stereochemistry of 1 and 2 was determined by applying the PGME method.

Euphorbiaceae↗
PubMed2001

Phyllanemblinins A-F, new ellagitannins from Phyllanthus emblica.

Six new ellagitannins, phyllanemblinins A-F (1-6), were isolated from Phyllanthus emblica, along with 30 known tannins and related compounds. Their structures were determined by spectral and chemical methods. Phyllanemblinins A (1) and B (2) were confirmed to be ellagitannins having a tetrahydroxybenzofuran dicarboxyl group and a hexahydroxydiphenoyl group, respectively, by chemical synthesis from furosin (8). Phyllanemblinin C (3) has a new acyl group at the glucose 2,4-positions and is structurally related to chebulagic acid. Phyllanemblinins D (4), E (5), and F (6) were found to be positional isomers of neochebuloyl 1(beta)-O-galloylglucose.

Antineoplastic Agents, Phytogenic↗
PubMed2001

Biochemical characterization of galloyl pedunculagin (ellagitannin) as a selective inhibitor of the beta-regulatory subunit of A-kinase in vitro.

The inhibitory effects of galloyl pedunculagin (GP) and eugeniin on the phosphorylation of histone H2B by cAMP-dependent protein kinase (A-kinase) and autophosphorylation of its beta-regulatory subunit (A-kinase beta) were examined in vitro. It was found that (i) GP (ID(50) = approx. 50 nM) effectively inhibits the activity of A-kinase (heterodimer), but high doses are required to inhibit the activities of the alpha-catalytic subunit (ID(50) = approx. 0.25 microM) and casein kinase II (CK-II, ID(50) = approx. 0.6 microM); (ii) GP inhibits the autophosphorylation of A-kinase beta in a dose-dependent manner with an ID(50) of approx. 6.6 nM, which is about 30-fold lower than that observed with CK-II beta; and (iii) GP reduces the suppressive effect of the beta-subunit on the activity of the alpha-subunit. In addition, purified bovine heart A-kinase precipitates when incubated with excess GP at pH 5.0. A similar precipitation of A-kinase was observed with eugeniin. These results show that the direct binding of GP to the beta-subunit prevents the physiological interaction between the beta- and alpha-subunits of A-kinase in vitro. This conclusion is presumably consistent with the binding affinity of proline-rich proteins with tannins, since A-kinase beta contains a proline-rich domain that interacts with GP or eugeniin. Therefore, GP will serve as a powerful inhibitor for in vitro and in vivo cellular studies of A-kinase beta-mediated signal transduction.

Animals↗
PubMed2001

Revised structure of cercidinin A, a novel ellagitannin having (R)-hexahydroxydiphenoyl esters at the 3,4-positions of glucopyranose.

The structure of cercidinin A, an ellagitannin isolated from the bark of Cercidiphyllum japonicum, was revised to 1,2,6-tri-O-galloyl-3,4-(R)-hexahydroxydiphenoyl-beta-D-glucose by two-dimensional NMR spectral analysis. Cercidinin A represents the first ellagitannin possessing a hexahydroxydiphenoyl group at the 3,4-positions of a modified 4C1-glucopyranose core.

Carboxylic Ester Hydrolases↗
PubMed2001

New phenolic constituents from the fruit juice of Phyllanthus emblica.

Six new phenolic constituents, L-malic acid 2-O- (1), mucic acid 2-O- (5), mucic acid 1,4-lactone 2-O- (6), 5-O- (8), 3-O- (10), and 3,5-di-O- (11) gallates, were isolated from the fruit juice of Phyllanthus emblica together with their methyl esters (2-4, 7, 9), and their structures were determined by spectral and chemical methods. Compounds 5, 6, and 8, the major phenolic constituents of the juice, were present as an equilibrium mixture in aqueous solution.

Antioxidants↗
PubMed2001

Alkaloids, diarylheptanoid and naphthalene carboxylic acid ester from Rhoiptelea chiliantha.

Two pyrrolidine alkaloids (1, 2) were isolated from the fruits of Rhoiptelea chiliantha Diel et Hand.-Mazz. (Rhoipteleaceae). A diphenyl ether-type diarylheptanoid (3), and a naphthalene carboxylic acid methyl ester (4) which is biogenetically-related to juglone were isolated from the branches of the same plant. Their chemical structures were elucidated on the basis of spectroscopic analysis and chemical evidence.

Alkaloids↗
PubMed2001

Caffeoyl, coumaroyl, galloyl, and hexahydroxydiphenoyl glucoses from Balanophora japonica.

Eighteen new and sixteen known acyl glucoses having caffeoyl, coumaroyl, galloyl, and hexahydroxydiphenoyl groups were isolated from a medicinal parasitic plant, Balanophora japonica. Their structures were determined by spectroscopic and chemical methods. Caffeoyl ellagitannins, which have been rarely found in nature, were major phenolic constituents of this plant, and this is the first report of the isolation of ellagitannins from Balanophoraceae.

Biphenyl Compounds↗
PubMed2000

Oxidation and epimerization of epigallocatechin in banana fruits.

To examine the metabolism of proanthocyanidins in banana fruit, (-)-epigallocatechin was treated with the homogenate of the fruit flesh to yield (-)-gallocatechin and an oxidation product, 1-(3,4,5-trihydroxyphenyl)-3-(2,4,6-trihydroxyphenyl)-2-hydroxy-1-propan one. The latter product is a stable form of a key intermediate in the oxidative metabolism of flavan-3-ols, and is also related to the biogenesis of A-type proanthocyanidins. In addition, treatment of the reaction mixture with o-phenylenediamine afforded monomeric and dimeric phenazine derivatives generated by condensation with the o-quinone form of the oxidation product.

Biotransformation↗
PubMed2000

Novel norsesquiterpenoids from the roots of Phyllanthus emblica.

Three ester glycosides, named phyllaemblicins A (3), B (4), and C (5), and a methyl ester (2), of a highly oxygenated norbisabolane, phyllaemblic acid (1), were isolated from the roots of Phyllanthus emblica, along with 15 tannins and related compounds. The structures of 2-5 were established by spectral and chemical methods.

China↗
PubMed2000

New monoterpene glycoside esters and phenolic constituents of Paeoniae radix, and increase of water solubility of proanthocyanidins in the presence of paeoniflorin.

Seven new monoterpene glycoside esters related to paeoniflorin were isolated from Paeoniae Radix, together with polymeric proanthocyanidins, polygalloylglucoses and 48 known compounds (a benzoylsucrose, seven aromatic acids, adenosine, nine monoterpene glycosides, eight flavan-3-ols, a catechin dimer formed by oxidation, seven proanthocyanidins, three galloylsucroses, five galloylglucoses, and six ellagitannins). The structures of the new compounds were determined by spectral investigation including two-dimensional NMR techniques. In addition, increased water solubility of polymeric proanthocyanidin in the presence of paeoniflorin was examined by n-octanol-water partition and 1H-NMR spectral experiments.

Anthocyanins↗
PubMed1999

Three novel C-glycosidic ellagitannins, rhoipteleanins H, I, and J, from rhoiptelea chiliantha

Three novel C-glycosidic ellagitannins named rhoipteleanins H (1), I (2), and J (3) were isolated from the fruits and bark of Rhoiptelea chiliantha Diels et Hand.-Mazz. (Rhoipteleaceae), and the structures were elucidated on the basis of detailed spectroscopic analysis and chemical evidence. Rhoipteleanin H possesses a unique cyclopentenone carboxyl moiety, which is probably formed by oxidation and subsequent rearrangement of an aromatic ring of a usual C-glycosidic ellagitannin. Rhoipteleanin I is the first ellagitannin having a hydroxynaphthalene glucoside moiety. Rhoipteleanin J is a dimeric ellagitannin generated by dehydrative coupling between two molecules of a monomeric C-glycosidic ellagitannin and subsequent oxidation of an aromatic ring. From a chemotaxonomic viewpoint, presence of these characteristic ellagitannins in this plant provides a further support for the establishment of the order Rhoipteleales comprising Rhoipteleaceae as the only family.

Journal Article↗
PubMed1998

Synthesis and antioxidant activity of novel amphipathic derivatives of tea polyphenol.

Hydrophobic derivatives of a tea polyphenol have been synthesized. 6, 8-Bis(octylthiomethyl)-epigallocatechin 3-O-gallate, 6, 8-bis(octylthiomethyl)-4 beta-(2-hydroxyethylthio)epigallocatechin 3-O-gallate and epigallocatechin 3-O-[4-O-(N-octadecylcarbamoyl)gallate] showed strong inhibition activity against lipid peroxidation of liposome caused by both lipid-soluble and water-soluble radical generators.

Antioxidants↗