Tannins and related compounds. CVII. Structure elucidation of three new monomeric and dimeric ellagitannins, flosin B and reginins C and D, isolated from Lagerstroemia flos-reginae Retz.

Abstract

Further chemical work on tannins in the leaves of Lagerstroemia flos-reginae RETZ. (Lythraceae) has resulted in the isolation of new monomeric (flosin B) and dimeric ellagitannins (reginins C and D), together with pterocarinin A (1) and 5-desgalloylpterocarinin A (2). On the basis of chemical and spectroscopic evidence, the structure of flosin B was determined to be a C-glycosidic ellagitannin (3) possessing a valoneic acid dilactonyl group, while reginins C and D were characterized as dimeric ellagitannins (6 and 10, respectively), in which a pedunculagin moiety is connected to pterocarinin A and casuarinin [the C-1 epimer of stachyurin (5)] moieties, respectively, through a carbon-to-oxygen bond.