FLAVAN AND PROCYANIDIN GLYCOSIDES FROM THE BARK OF BLACKJACK OAK

The bark of blackjack oak contains (+)-catechin, (-)-epicatechin, (+)- 3-O-[beta-D-glucopyranosyl]catechin, catechin-(4 alpha-->8)-catechin, epicatechin-(4 beta-->8)-catechin as well as the novel 3-O-[beta-D-glu copyranosyl]catechin-(4 alpha-->8)-catechin and a-L-rhamnopyranosyl-(1 -->6)-beta-D-glucopyranosyl] -catechin, as major components. The latte r rutinoside of catechin is especially interesting because of the exce ptionally small J(2,3) C-ring coupling. The glucoside of catechin-(4 a lpha-->8)-catechin is only the second proanthocyanidin found in nature in which a 3-O-glycoside is present in the upper 'extender unit' of a dimer.