Polymer-like polyphenols of black tea and their lipase and amylase inhibitory activities |
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Authors: | Kusano Rie Andou Hisashi Fujieda Miho Tanaka Takashi Matsuo Yosuke Kouno Isao |
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Affiliation: | Graduate School of Biomedical Sciences, Nagasaki University, 1-14 Bunkyo Machi, Nagasaki 852-8521, Japan. |
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Abstract: | 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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