Tannins and Related Compounds. XXXVIII.₁₎ Isolation and Characterization of Flavan-3-ol Glucosides and Procyanidin Oligomers from Cassia Bark (Cinnamomum cassia Blume)

A chemical examination of the bark of Cinnamomum cassia: Lauraceae) has led to the isolation of three flavan-3-ol glucosides (1—3) and three oligomeric procyanidins (4—6) named cinnamtannins A₂-A₄, together with (—) -epicatechin(7), procyanidins B-2 (8), B-5 (9) and C-l (11), and a doubly-linked proanthocyanidin (10). On the basis of chemical and spectroscopic evidence, compounds 1—3 were characterized as (—) -epicatechin 3-O-, 8-C- and 6-C-b-D-glucopyranosides, respectively, while compounds 4—6 were shown to be tetrameric, pentameric and hexameric procyanidins, respectively, consisting exclusively of (—) -epicatechin units linked linearly through C(4b)-C(8) bonds.