title: Major water-soluble polyphenols, proanthocyanidins, in leaves of persimmon (Diospyros kaki) and their alpha-amylase inhibitory activity.
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.
authors.affiliation: Department of Food Science, Niigata University of Pharmacy and Applied Life Sciences.
authors.forename: Kayoko
authors.initials: K
authors.lastname: Kawakami
authors.forename: Saiko
authors.initials: S
authors.lastname: Aketa
authors.forename: Mitsuhiro
authors.initials: M
authors.lastname: Nakanami
authors.forename: Shinzo
authors.initials: S
authors.lastname: Iizuka
authors.forename: Masao
authors.initials: M
authors.lastname: Hirayama
mesh_terms: D000818:Animals; D001786:Blood Glucose / Q000378:metabolism; D002851:Chromatography, High Pressure Liquid; D029788:Diospyros / Q000737:chemistry* / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000737:chemistry* / Q000378:metabolism / Q000494:pharmacology*; D005419:Flavonoids / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D008297:Male; D010636:Phenols / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D010936:Plant Extracts / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D018515:Plant Leaves / Q000737:chemistry* / Q000378:metabolism; D059808:Polyphenols; D044945:Proanthocyanidins / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D012621:Seasons; D012995:Solubility; D013213:Starch / Q000008:administration & dosage; D014867:Water / Q000737:chemistry*; D000516:alpha-Amylases / Q000037:antagonists & inhibitors*
chemical_list: D001786:Blood Glucose; D004791:Enzyme Inhibitors; D005419:Flavonoids; D010636:Phenols; D010936:Plant Extracts; D059808:Polyphenols; D044945:Proanthocyanidins; D014867:Water; C013221:proanthocyanidin; D013213:Starch; D000516:alpha-Amylases