Major Water-Soluble Polyphenols, Proanthocyanidins, in Leaves of Persimmon (<i>Diospyros kaki</i>) and Their α-Amylase Inhibitory Activity
Kayoko Kawakami, Saiko Aketa, Mitsuhiro NAKANAMI, Shinzo IIZUKA, Masao Hirayama
Bioscience Biotechnology and Biochemistry
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 alpha-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.
Extracted Claims
2 claims extracted from this paper into the knowledge graph
proanthocyanidin oligomers inhibit pancreas alpha-amylase
“This effect is considered to be due to inhibition of pancreas alpha-amylase.”
persimmon leaf tea decreases blood glucose level
“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.”