Abstract
Four polymeric tannins prepared from young fruits of persimmon, banana, carob bean and Chinese quince were shown, in addition to having some properties of condensed tannins, to produce precipitate in methanolic solution by addition of K2HPO4, to form anthocyanidins on acid treatment, and to release the thioethers of flavan-3- ols by means of toluene-α-thiol treatment. It is suggested from these results that each tannin is a proanthocyanidin polymer and should be called flavanan or flavonan tannin instead of condensed tannin. Among the fruit tannins tested, loquat-tannin was an exception; it appeared to be a proanthocyanidin oligomer.
Three methylated tannins from young fruits of banana, carob bean and Chinese quince were similar in molecular size (Mw=1.4-1.0×104, Mn=0.7-0.2×104), while methylated kaki-tannin is thought to be a slightly higher polymer.
In comparison with kaki-tannin which mainly consists of catechin, catechin-3-gallate, gallocatechin and gallocatechin-3-gallate with the ratio of about 1:1.2:2.1:2.2, banana-tannin consists of catechin and gallocatechin with the ratio of about 1 to 1.3 and carob bean-tannin consists of catechin-3-gallate, gallocatechin and gallocatechin-3-gallate with the ratio of about 1:3.3:4.6. Chinese quince- and loquat-tannin appear to be composed of only catechin.
