Tannins and related compounds. LXI. Isolation and structures of novel bi- and triflavanoids from the leaves of Cassia fistula L.

Abstract

Together with (-)-epiafzelechin (1) and its 3-O-glucoside (4), (-)-epicatechin (2) and procyanidin B-2 (3), seven new biflavanoids (5-7, 9-12) and two triflavanoids (8, 13) have been isolated from the leaves of Cassia fistula L.(Leguminosae). On the basis of chemical and spectroscopic evidence, the structures of 5-8 were established to be proanthocyanidins each having (-)-epiafzelechin unit(s) in the molecule, while 9-13 were shown to consist of (2S)-7, 4'-dihydroxyflavan and (-)-epiafzelechin units.