Tannins and Related Compounds. XXXI. Isolation and Characterization of Proanthocyanidins in Kandelia candel (L.) Druce

Together with propelargonidin dimers (14,15 and 16), and procyanidin trimers (23, 24 and 25) of common types, two novel proanthotyanidin dimers, kandelins A-1 (12) and A-2 (13), and four trimers, kandelins B-1 (19), B-2 (20), B-3 (21) and B-4 (22), which all contain a phenylpropanoid substituent in the upper flavan unit, have been isolated from the bark of Kandelia candel (L.) DRUCE(Rhizophoraceae). Spectroscopic evidence combined with chemical studies involving acid-catalyzed thiolytic degradation permitted the assignment of their structures. The presence in this plant source of flavan-3-ols, (+)-afzelechin (2), (+)-catechin (3), (—)-epicatechin (4) and (-b)-gallocatechin (5), known proanthocyanidins B-1 (8), B-2 (9), C-1 (17) and trimer (18), and cinchonains la (6), lb (7), Ila (10) and lIb (11) was also demonstrated.