The Chemical Structure of Kaki-tannin from Immature Fruit of the Persimmon (Diospyros kaki L.)

A partially purified tannin was prepared by a K2HP04-precipitation method from immature persimmon fruit (Diospyros kaki L., cv. “Hiratanenashi,” astringent type). The kaki-tannin gave delphinidin and eyanidin on acid hydrolysis. Its methylated derivative showed vmax 1720 cm−1 in IR spectrum and had the molecular weight of ca. 1.38 × l04 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 interflavan linkage from C–4 of one unit to C–6 or C–8 of another unit.