Bioscience, Biotechnology, and Biochemistry
Online ISSN : 1347-6947
Print ISSN : 0916-8451
Food & Nutrition Science Regular Papers
Major Water-Soluble Polyphenols, Proanthocyanidins, in Leaves of Persimmon (Diospyros kaki) and Their α-Amylase Inhibitory Activity
Kayoko KAWAKAMISaiko AKETAMitsuhiro NAKANAMIShinzo IIZUKAMasao HIRAYAMA
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2010 Volume 74 Issue 7 Pages 1380-1385

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Abstract

The amounts and compositions of polyphenol in persimmon leaves and persimmon leaf tea were investigated. The predominant polyphenols in fresh leaves were water-soluble, and the contents reached a maximum (2.40% w/w) in June, and then gradually decreased. Separation of them followed by thiolytic degradation revealed that the major components were unique proanthocyanidin oligomers consisting of four heterogeneous extension units, including epigallocatechin-3-O-gallate. Persimmon leaf tea also contained similar proanthocyanidins with similar compositional units. Oral administration of starch with polyphenol concentrate of persimmon leaf tea resulted in a significant and dose-dependent decrease in the blood glucose level in Wistar rats. This effect is considered to be due to inhibition of pancreas α-amylase. These results indicate that persimmon leaf tea containing peculiar proanthocyanidins has a significant role in suppressing blood glucose elevation after starch intake, and that the best harvest time is June.

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© 2010 by Japan Society for Bioscience, Biotechnology, and Agrochemistry
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