The chemical structure of kaki-tannin from immature fruit of the persimmon (Diospyros kaki L.).

Abstract

A partially purified tannin was prepared by a K2HPO4-precipitation method from immature persimmon fruit (Diospyros kaki L., cv. “Hiratanenashi, ” astringent type). The kaki-tannin gave deiphinidin and cyanidin on acid hydrolysis. Its methylated derivative showed vmax 1720cm-1 in IR spectrum and had the molecular weight of ca. 1.38×104 daltons in Mw. From the results of toluene-α-thiol treatment, it is suggested that the kaki-tannin consists of catechin, catechin-3-gallate, gallocatechin, gallocatechin-3-gallate and an unknown terminal residue, and belongs to proanthocyanidin B group with a carbon-carbon interfiavan linkage from C-4 of one unit to C-6 or C-8 of another unit.