Cornusiin A, a dimeric ellagitannin forming four tautomers, and accompanying new tannins in Cornus officinalis.

Abstract

Cornusiin A (4), a dimeric ellagitannin which forms four anomeric isomers, have been isolated from Cornus officinalis fruits, along with cornusiin B (5) and related compounds. Their structures and the ratio of tautomers in the equilibrium mixture of 4 were determined. Oenothein C (8), which was produced by partial hydrolysis of 5, has been isolated also from Oenothera erythrosepala leaves.