Publications by authors named "Isao Kouno"

54 Publications

Antioxidant and hyaluronidase inhibitory activities of diverse phenolics in Phyllanthus emblica.

Nat Prod Res 2016 Dec 12;30(23):2726-2729. Epub 2016 Feb 12.

a State Key Laboratory of Phytochemistry & Plant Resources in West China , Kunming Institute of Botany, Chinese Academy of Sciences , Kunming , People's Republic of China.

Fifty-eight phenolic compounds isolated from Phyllanthus emblica were screened and compared for their in vitro and in vivo antioxidant properties, as well as hyaluronidase (HAase) inhibitory activities. Among them, 20 compounds showed to be promising antioxidants due to the stronger scavenging activity in both DPPH radical and Danio rerio reactive oxygen species assays, while nine compounds were potential HAase inhibitors with 100-fold stronger activities than that of the positive control, DSCG. The structure activity relationship was discussed.
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http://dx.doi.org/10.1080/14786419.2015.1137573DOI Listing
December 2016

Two new oleanane-type triterpenes isolated from Japanese post-fermented tea produced by anaerobic microbial fermentation.

Molecules 2013 Apr 24;18(5):4868-75. Epub 2013 Apr 24.

Department of Natural Product Chemistry, Graduate School of Biomedical Sciences, Nagasaki University, 1-14 Bunkyo-machi, Nagasaki 852-8521, Japan.

Four triterpenes were isolated from a traditional Japanese tea product produced by anaerobic microbial fermentation of heated green tea leaves (Camellia sinensis). Two of the compounds were novel and characterized by spectroscopic investigation to be 13,26-epoxy-3β,11α-dihydroxyolean-12-one and 3β,11α,13β-trihydroxyolean-12-one. Two known triterpenes were identified as taraxastane-3β,20β-diol and taraxastane-3β,20α-diol. These triterpenes were not detected in the original green tea leaves.
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http://dx.doi.org/10.3390/molecules18054868DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6270010PMC
April 2013

New bisabolane sesquiterpene from the mycelia of Amanita virgineoides.

Chem Pharm Bull (Tokyo) 2013 ;61(3):366-9

Graduate School of Biomedical Sciences, Division of Natural Product Chemistry, Nagasaki University, Nagasaki, Japan.

A bisabolane type of sesquiterpene was isolated from the culture medium of Amanita virgineoides BAS, together with two known compounds, including lignoren, and harziandion. The structure of the new compound "virgineol" was established using a combination of different NMR spectroscopy techniques, whereas the chemical structure of the known compound was identified as lignoren, and the structure of harziandion was confirmed by X-ray crystallographic analysis.
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http://dx.doi.org/10.1248/cpb.c12-01070DOI Listing
December 2013

Formation and conformation of baicalin-berberine and wogonoside-berberine complexes.

Chem Pharm Bull (Tokyo) 2012 ;60(6):706-11

State Key Laboratory of Quality Research in Chinese Medicine, Macau Institute for Applied Research in Medicine and Health, Macau University of Science and Technology, China.

It is well-known that baicalin-berberine complex (1) precipitates in the water decoction of numerous Chinese Medicinal formulae containing Radix Scutellariae and Rhizoma Coptidis or Cortex Phellodendri. In the current study, ionic interaction between the carboxylate ion of baicalin and the quaternary ammonium ion of berberine was revealed to be responsible for the formation of 1 and wogonoside-berberine (2) by using FAB-MS and NMR titration experiments. In addition, nuclear Overhauser effect spectroscopy (NOESY) correlations observed in 1 and 2 suggested quite different conformation of the two complexes, which was further supported by the fact that the [α](D) of the canadine obtained by reduction of 1 is of an opposite sign to that obtained from 2. Partition coefficients (n-octanol/water) determination demonstrated 12-20 times larger partition coefficient of each complex (1, 2) than that of each single compound (baicalin, wogonoside, and berberine), indicating the significant role of the formation of the complex in the bioavailability enhancement of these pharmacologically active constituents.
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http://dx.doi.org/10.1248/cpb.60.706DOI Listing
October 2012

Benzyl benzoate glycoside and 3-deoxy-D-manno-2-octulosonic acid derivatives from Solidago decurrens.

J Nat Prod 2012 Jan 20;75(1):88-92. Epub 2011 Dec 20.

Graduate School of Biomedical Sciences, Course of Pharmaceutical Science, Nagasaki University, 1-14 Bunkyo-machi, Nagasaki 852-8521, Japan.

A new benzyl benzoate glycoside and five new 3-deoxy-D-manno-2-octulosonic acid derivatives were isolated from the entire plant of Solidago decurrens together with three known compounds. Their structures were established by extensive analyses of their 1D and 2D NMR spectra and by comparison with physical data of known compounds.
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http://dx.doi.org/10.1021/np2007582DOI Listing
January 2012

A new catechin oxidation product and polymeric polyphenols of post-fermented tea.

Food Chem 2011 Dec 12;129(3):830-6. Epub 2011 May 12.

Department of Natural Product Chemistry, Graduate School of Biomedical Sciences, Nagasaki University, 1-14 Bunkyo Machi, Nagasaki 852-8521, Japan.

A new epicatechin oxidation product with a 3,6-dihydro-6-oxo-2H-pyran-2-carboxylic acid moiety was isolated from a commercially available post-fermented tea that is produced by microbial fermentation of green tea. The structure of this product was determined by spectroscopic methods. A production mechanism that includes the oxygenative cleavage of the catechol B-ring of (-)-epicatechin is proposed. In addition, polymeric polyphenols were separated from the post-fermented tea and partially characterised by (13)C NMR spectroscopy and gel-permeation chromatography. The polymers appear to be primarily composed of epigalloacetechin-3-O-gallate and the molecular weight (Mn) of the acetylated form was estimated to be ∼3500.
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http://dx.doi.org/10.1016/j.foodchem.2011.05.031DOI Listing
December 2011

Biomimetic one-pot preparation of a black tea polyphenol theasinensin A from epigallocatechin gallate by treatment with copper(II) chloride and ascorbic acid.

Chem Pharm Bull (Tokyo) 2011 ;59(9):1183-5

Graduate School of Biomedical Sciences, Nagasaki University, Japan.

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.
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http://dx.doi.org/10.1248/cpb.59.1183DOI Listing
January 2012

Triterpene hexahydroxydiphenoyl esters and a quinic acid purpurogallin carbonyl ester from the leaves of Castanopsis fissa.

Phytochemistry 2011 Nov 8;72(16):2006-14. Epub 2011 Aug 8.

Graduate School of Biomedical Sciences, Nagasaki University, 1-14 Bunkyo-Machi, Nagasaki 852-8521, Japan.

Triterpene hexahydroxydiphenoyl (HHDP) esters have only been isolated from Castanopsis species, and the distribution of these esters in nature is of chemotaxonomical interest. In this study, the chemical constituents of the leaves of Castanopsis fissa were examined in detail to identify and isolate potential HHDP esters. Together with 53 known compounds, 3,4-di-O-galloyl-1-O-purpurogallin carbonyl quinic acid (1) and 3,24-(S)-HHDP-2α,3β,23,24-tetrahydroxytaraxastan-28,20β-olide (2) were isolated and their structures were elucidated by spectroscopic and chemical methods. The polyphenols of the leaves were mainly composed of galloyl quinic acids, triterpenes HHDP esters, ellagitannins and flavonol glycosides. In particular, the isolation yields of 1,3,4-trigalloyl quinic acid and compound 2 were 1.53% and 0.27%, respectively, from the fresh leaves. The presence of lipid soluble HHDP esters of oleanane-type triterpenes as one of the major metabolites is an important chemotaxonomical discovery. Lipase inhibition activities and ORAC values of the major constituents were compared. The triterpene HHDP ester showed moderate lipase inhibition activity and myricitrin gave the largest ORAC value.
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http://dx.doi.org/10.1016/j.phytochem.2011.07.007DOI Listing
November 2011

Polyphenol composition of a functional fermented tea obtained by tea-rolling processing of green tea and loquat leaves.

J Agric Food Chem 2011 Jul 8;59(13):7253-60. Epub 2011 Jun 8.

Graduate School of Biomedical Sciences, Nagasaki University, Nagasaki, Japan.

Phenolic constituents of a new functional fermented tea produced by tea-rolling processing of a mixture (9:1) of tea leaves and loquat leaves were examined in detail. The similarity of the phenolic composition to that of black tea was indicated by high-performance liquid chromatography comparison with other tea products. Twenty-five compounds, including three new catechin oxidation products, were isolated, and the structures of the new compounds were determined to be (2R)-2-hydroxy-3-(2,4,6-trihydroxyphenyl)-1-(3,4,5-trihydroxyphenyl)-1-propanone 2-O-gallate, dehydrotheasinensin H, and acetonyl theacitrin A by spectroscopic methods. In addition, theacitrinin A and theasinensin H were obtained for the first time from commercial tea products. Isolation of these new and known compounds confirms that reactions previously demonstrated by in vitro model experiments actually occur when fresh tea leaves are mechanically distorted and bruised during the production process.
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http://dx.doi.org/10.1021/jf201499nDOI Listing
July 2011

ent-Eudesmane sesquiterpenoids, galloyl esters of the oak lactone precursor, and a 3-O-methylellagic acid glycoside from the wood of Platycarya strobilacea.

Phytochemistry 2011 Jun;72(8):796-803

Graduate School of Biomedical Sciences, Nagasaki University, Nagasaki, Japan.

ent-Eudesmane sesquiterpenoids, 8,11-dihydroxy-2,4-cycloeudesmane, 11-hydroxy-2,4-cycloeudesman-8-one and 2,4-cyclo-7(11)-eudesmen-8-one, were isolated from the wood of Platycarya strobilacea, which has been used as an aromatic tree since at least the 18th century. On charring the wood, 2,4-cyclo-7(11)-eudesmen-8-one was detected in the smoke. In the charred wood, the concentrations of ellagitannins, such as galloyl pedunculagin, dramatically decreased, whereas concentrations of pentagalloyl glucose, and other gallotannins were relatively stable. In addition, two other compounds, the 6'-O-m- and p-digalloyl oak lactone precursor and the 3-O-methylellagic acid 4'-O-(4″-O-galloyl)-xylopyranoside, were isolated from the charred wood along with m- and p-digallic acid.
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http://dx.doi.org/10.1016/j.phytochem.2011.02.020DOI Listing
June 2011

New phenolic compounds from Camellia sinensis L. leaves fermented with Aspergillus sp.

J Nat Med 2011 Jul 15;65(3-4):594-7. Epub 2011 Feb 15.

Department of Applied Biological Sciences, Saga University, Saga, Japan.

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.
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http://dx.doi.org/10.1007/s11418-011-0515-0DOI Listing
July 2011

New diketopiperazine derivatives isolated from sea urchin-derived bacillus sp.

Chem Pharm Bull (Tokyo) 2011 ;59(1):106-8

Garden for Medicinal Plants, Graduate School of Biomedical Sciences, Nagasaki University, Bunkyou-machi, Nagasaki, Japan.

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.
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http://dx.doi.org/10.1248/cpb.59.106DOI Listing
April 2011

α-Amylase and lipase inhibitory activity and structural characterization of acacia bark proanthocyanidins.

J Nat Prod 2011 Feb 30;74(2):119-28. Epub 2010 Dec 30.

Laboratory of Natural Product Chemistry, Graduate School of Biomedical Sciences, Nagasaki University, 1-14 Bunkyo-Machi, Nagasaki 852-8521, Japan.

The bark extract of Acacia mearnsii showed strong lipase and α-amylase inhibition activities. Fractionation of the extract by column chromatography and subsequent (13)C NMR and MALDI-TOF-MS analysis revealed that the active substances are proanthocyanidin oligomers mainly composed of 5-deoxyflavan-3-ol units. In addition, 4'-O-methylrobinetinidol 3'-O-β-D-glucopyranoside, fisetinidol-(4α,6)-gallocatechin, and epirobinetinidol-(4β,8)-catechin were isolated as new compounds, and their structures were determined from spectroscopic data. Furthermore, a modified thiol degradation method using strongly acidic conditions was applied to the extract to yield three thiol degradation products derived from robinetinidol units. This method is useful for characterizing acacia proanthocyanidins (wattle tannins).
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http://dx.doi.org/10.1021/np100372tDOI Listing
February 2011

New iridoid diesters of glucopyranose from Linaria canadensis (L.) Dum.

J Nat Med 2011 Jan 16;65(1):172-5. Epub 2010 Jul 16.

Department of Applied Biological Sciences, Faculty of Agriculture, Saga University, 1 Honjo, Saga 840-8502, Japan.

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.
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http://dx.doi.org/10.1007/s11418-010-0441-6DOI Listing
January 2011

Chemistry of secondary polyphenols produced during processing of tea and selected foods.

Int J Mol Sci 2009 Dec 28;11(1):14-40. Epub 2009 Dec 28.

Nagasaki University, Japan.

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.
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http://dx.doi.org/10.3390/ijms11010014DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2820987PMC
December 2009

Reaction of the black tea pigment theaflavin during enzymatic oxidation of tea catechins.

J Nat Prod 2010 Jan;73(1):33-9

Laboratory of Natural Product Chemistry, Graduate School of Biomedical Sciences, Nagasaki University, Bunkyo-Machi 1-14, Nagasaki 852-8521, Japan.

Degradation of the black tea pigment theaflavin was examined in detail. Enzymatic oxidation of a mixture of epigallocatechin and epicatechin initially produced theaflavin, while prolonged reaction decreased the product. Addition of ethanol to the reaction mixture at the point when theaflavin began to decrease afforded four new products, together with theanaphthoquinone, a known oxidation product of theaflavin. The structures of the new products were determined by spectroscopic methods. One of the products was an ethanol adduct of a theanaphthoquinone precursor, and this reacted with theaflavin to give two further products. A product generated by coupling of theaflavin with epicatechin quinone was also obtained. The structures of the products indicate that oxidation and coupling with quinones are key reactions in the degradation of theaflavins. The degradation of theaflavin probably contributes to production of thearubigins.
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http://dx.doi.org/10.1021/np900618vDOI Listing
January 2010

Dammarane-type triterpene saponins from the flowers of Panax notoginseng.

Molecules 2009 Jun 10;14(6):2087-94. Epub 2009 Jun 10.

School of Chinese Medicine, Hong Kong Baptist University, Kowloon Tong, Hong Kong, China.

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.
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http://dx.doi.org/10.3390/molecules14062087DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6254266PMC
June 2009

Coupling reactions of catechins with natural aldehydes and allyl alcohols and radical scavenging activities of the triglyceride-soluble products.

J Agric Food Chem 2009 Jul;57(14):6417-24

Department of Natural Product Chemistry, Graduate School of Biomedical Sciences, Nagasaki University, Nagasaki 852-8521, Japan.

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.
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http://dx.doi.org/10.1021/jf9010998DOI Listing
July 2009

Increase of theaflavin gallates and thearubigins by acceleration of catechin oxidation in a new fermented tea product obtained by the tea-rolling processing of loquat ( Eriobotrya japonica ) and green tea leaves.

J Agric Food Chem 2009 Jul;57(13):5816-22

Graduate School of Biomedical Sciences, Nagasaki University, 1-14 Bunkyo-machi, Nagasaki 852-8521, Japan.

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.
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http://dx.doi.org/10.1021/jf900963pDOI Listing
July 2009

Euscaphinin, a new ellagitannin dimer from Euscaphis japonica (THUNB.) KANITZ.

Chem Pharm Bull (Tokyo) 2009 Apr;57(4):421-3

Graduate School of Biomedical Sciences, Nagasaki University, Nagasaki, Japan.

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.
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http://dx.doi.org/10.1248/cpb.57.421DOI Listing
April 2009

Isolation and structure of whiskey polyphenols produced by oxidation of oak wood ellagitannins.

J Agric Food Chem 2008 Aug 2;56(16):7305-10. Epub 2008 Aug 2.

Graduate School of Biomedical Sciences, Nagasaki University, 1-14 Bunkyo-machi, Nagasaki 852-8521, Japan.

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.
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http://dx.doi.org/10.1021/jf8012713DOI Listing
August 2008

Caffeoyl arbutin and related compounds from the buds of Vaccinium dunalianum.

Phytochemistry 2008 Dec 17;69(18):3087-94. Epub 2008 Jul 17.

Laboratory of Natural Product Chemistry, Graduate School of Biomedical Sciences, Nagasaki University, Bunkyo Machi 1-14, Nagasaki 852-8521, Japan.

Dunalianosides A-I (1-9), esters of arbutin and related phenolic glucosides, were isolated from the buds of Vaccinium dunalianum Wight (Ericaceae) together with 20 known compounds, and their structures were established on the basis of 1- and 2D NMR spectroscopic evidence. Dunalianosides F-H were dimers of p-hydroxyphenyl 6-O-trans-caffeoyl-beta-D-glucopyranoside (10). The latter was obtained in extraordinary high yield (22% of dry weight), and dunalianoside I (9) was found to be a conjugate of arbutin with an iridoid glucoside.
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http://dx.doi.org/10.1016/j.phytochem.2008.06.001DOI Listing
December 2008

Structure of polymeric polyphenols of cinnamon bark deduced from condensation products of cinnamaldehyde with catechin and procyanidins.

J Agric Food Chem 2008 Jul 18;56(14):5864-70. Epub 2008 Jun 18.

Graduate School of Biomedical Sciences, Department of Molecular Medicinal Sciences, Nagasaki University, 1-14 Bunkyo-machi, Nagasaki 852-8521,

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.
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http://dx.doi.org/10.1021/jf800921rDOI Listing
July 2008

Two new maltol glycosides and cyanogenic glycosides from Elsholtzia rugulosa Hemsl.

J Nat Med 2008 Jan 9;62(1):75-8. Epub 2007 Aug 9.

Graduate School of Biomedical Sciences, Nagasaki University, 1-14 Bunkyo-Machi, Nagasaki, 852-8521, Japan.

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.
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http://dx.doi.org/10.1007/s11418-007-0188-xDOI Listing
January 2008

Polymer-like polyphenols of black tea and their lipase and amylase inhibitory activities.

Chem Pharm Bull (Tokyo) 2008 Mar;56(3):266-72

Graduate School of Biomedical Sciences, Nagasaki University, 1-14 Bunkyo Machi, Nagasaki 852-8521, Japan.

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.
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http://dx.doi.org/10.1248/cpb.56.266DOI Listing
March 2008

Cytotoxic hydrolyzable tannins from Balanophora japonica.

J Nat Prod 2008 Apr 27;71(4):719-23. Epub 2008 Feb 27.

School of Chinese Medicine, Hong Kong Baptist University, Kowloon Tong, People's Republic of China.

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.
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http://dx.doi.org/10.1021/np070519+DOI Listing
April 2008

Bicyclic polyketide lactones from Chinese medicinal ants, Polyrhacis lamellidens.

J Nat Prod 2008 Apr 26;71(4):724-7. Epub 2008 Feb 26.

School of Chinese Medicine, Hong Kong Baptist University, Kowloon Tong, Hong Kong, People's Republic of China.

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.
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http://dx.doi.org/10.1021/np070558lDOI Listing
April 2008

Trypanocidal activity of extracts and compounds from the stem bark of Anogeissus leiocarpus and Terminalia avicennoides.

Parasitol Res 2008 Mar 9;102(4):697-703. Epub 2007 Dec 9.

Natural Product Chemistry, Graduate School of Biomedical Sciences, Nagasaki University, Nagasaki-shi, Japan.

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.
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http://dx.doi.org/10.1007/s00436-007-0815-1DOI Listing
March 2008

Structures of epicatechin gallate trimer and tetramer produced by enzymatic oxidation.

Chem Pharm Bull (Tokyo) 2007 Dec;55(12):1768-72

Graduate School of Biomedical Sciences, Nagasaki University, 1-14 Bunkyo-machi. Nagasaki 852-8521, Japan.

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.
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http://dx.doi.org/10.1248/cpb.55.1768DOI Listing
December 2007

Enzymatic oxidation of gallocatechin and epigallocatechin: effects of C-ring configuration on the reaction products.

Phytochemistry 2008 Dec 20;69(18):3054-61. Epub 2007 Sep 20.

Graduate School of Biomedical Sciences, Nagasaki University, 1-14 Bunkyo-machi, Nagasaki 852-8521, Japan.

Tea leaf is rich in pyrogallol-type catechins, and their oxidation is important in the generation of black tea polyphenols. In the present study, the enzymatic oxidation of three pyrogallol-type catechins, (+)- and (-)-gallocatechins and (-)-epigallocatechin, was compared. The reactions yielded unstable quinone products, which were trapped as condensation products with o-phenylenediamine. The oxidation of (+)-gallocatechin proceeded very slowly compared to the reaction of (-)-epigallocatechin, and yielded a proepitheaflagallin-type dimer as the major product, though oxidation of (-)-epigallocatechin gave predominantly dehydrotheasinensin C. The cis-configuration of the C-3 hydroxyl group and the B-ring of (-)-epigallocatechin was apparently crucial for rapid and selective production of dehydrotheasinensin C. Oxidation of (-)-gallocatechin proceeded in a manner similar to that of (+)-gallocatechin, and produced an enantiomer of the (+)-gallocatechin product. The results suggest that enzymes catalyze oxidation of the pyrogallol B-ring to the o-quinone, with subsequent non-enzymatic coupling reactions proceed under highly steric control.
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http://dx.doi.org/10.1016/j.phytochem.2007.08.007DOI Listing
December 2008