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Saga-shi, Japan

Yasuda M.,Nishikyushu University | Yasutake K.,Nishikyushu University | Hino M.,Nishikyushu University | Ohwatari H.,Nishikyushu University | And 4 more authors.
Food Chemistry | Year: 2014

Water chestnut is an annual aquatic plant that grows in Asia and Europe. Although water chestnut has been used as food and herbal medicine, its physiological functions and active ingredients are unknown. Here, we extracted polyphenols from the husk of the Japanese water chestnut (Trapa japonica) and assessed their effects on blood glucose levels. Three hydrolysable polyphenolics (WCPs), eugeniin, 1,2,3,6-tetra-O-galloyl-β-d-glucopyranose, and trapain, were predominant with dry-weight contents of 2.3 ± 0.0, 2.7 ± 0.1, and 1.2 ± 0.1 g/100 g, respectively. These WCPs exhibited inhibitory activity against α-amylase and α-glucosidase. Whereas (-)-epigallocatechin gallate does not inhibit α-amylase, WCPs exhibited high inhibitory activity (>80% at 0.15 mg/mL). In mice, administration of WCPs (40 mg/kg) significantly reduced blood glucose and serum insulin levels as assessed by the carbohydrate tolerance test. © 2014 Elsevier Ltd. All rights reserved. Source


Yamaguchi S.,Kwansei Gakuin University | Hirokane T.,Kwansei Gakuin University | Yoshida T.,Okayama University of Science | Tanaka T.,Nagasaki University | And 4 more authors.
Journal of Organic Chemistry | Year: 2013

Prompted by the outcome that the synthesized roxbin B was not identical to the natural roxbin B, the structural determination process and spectral data were re-examined, with the finding that roxbin B was very likely to be 1-O-galloyl-2,3-(R);4,6-(S)-bis-O-hexahydroxydiphenoyl-β-d-glucose (cuspinin). Because the (R)-axial chirality is rare in natural products when the hexahydroxydiphenoyl group bridges the 2- and 3-oxygens, the proposed structure of cuspinin was confirmed by the total synthesis, leading to the conclusion that roxbin B is the same as cuspinin. © 2013 American Chemical Society. Source


Huang Y.-L.,Nagasaki University | Huang Y.-L.,Guangxi Institute of Botany | Matsuo Y.,Nagasaki University | Tanaka T.,Nagasaki University | And 3 more authors.
Heterocycles | Year: 2011

In the course of a chemotaxonomical study of Chinese Castanopsis species, two previously unknown flavan-3-ols, named sclerophynins A and B, were isolated from the leaves of C. sclerophylla, together with five related known compounds. On the basis of spectroscopic analysis, the new compounds were characterized to be (4S,8R,9S)-4-(3,4-dihydroxyphenyl)-8-(3,4,5-trihydroxyphenyl)- 3,4,9,10-tetrahydro-5,9-dihydroxy-2H,8H-benzo[1,2-b:3,4-b']dipyran-2- one and (4S,7S,8R)-4,8-bis(3,4-dihydroxyphenyl)-3,4,6,7-tetrahydro-5-glucopyranosyloxy- 7-hydroxy-2H,8H-benzo[1,2-b:5,4-b']dipyran-2-one, respectively. © 2011 The Japan Institute of Heterocyclic Chemistry. Source


Huang Y.-L.,Nagasaki University | Huang Y.-L.,CAS Institute of Botany | Tsujita T.,Nagasaki University | Tanaka T.,Nagasaki University | And 4 more authors.
Phytochemistry | Year: 2011

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. © 2011 Elsevier Ltd. All rights reserved. Source


Huang Y.-L.,Nagasaki University | Huang Y.-L.,Guangxi Institute of Botany | Tanaka T.,Nagasaki University | Matsuo Y.,Nagasaki University | And 3 more authors.
Phytochemistry Letters | Year: 2012

In the course of a chemotaxonomical study of Castanopsis species (Fagaceae), detailed investigation of the leaves of C. sclerophylla led to isolation of three new phenolic compounds together with 62 known compounds. The structures of the new compounds were elucidated as 2-O-galloyl-O-4,6-(S)- valoneoyl-d-glucose (1), 6-O-galloyl-1-O-vanilloyl-β-d-glucose (2), and 4″-O-galloylchestanin (3) by means of spectroscopic analyses and enzymatic hydrolysis with tannase. Comparison with other Castanopsis species indicated that C. sclerophylla characteristically accumulates chlorogenic acid and a dimeric ellagitannin, rugosin E. Triterpene hexahydroxydiphenoyl esters, which are major constituents of C. cuspidata var. sieboldii, C. hystrix, and C. fissa were not detected. © 2011 Phytochemical Society of Europe. Published by Elsevier B.V. All rights reserved. Source

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