Tannins and related compounds. Part 37. Isolation and structure elucidation of elaeocarpusin, a novel ellagitannin from Elaeocarpus sylvestris var. Ellipticus

A new hydrolysable tannin, elaeocarpusin, isolated from the leaves of Elaeocarpus sylvestris var. Ellipticus, has been characterized on the basis of chemical, spectroscopic, and X-ray analyses to be a novel ellagitannin in which a unique acid ester group probably derived by a condensation of a hexahydroxydiphenoyl group and dehydroascorbic acid is attached to the 2,4-positions of 1-O-galloyl- 3,6-(R)-hexahydroxydiphenoyl-D-glucopyranose (corilagin). This structural feature suggests the pos- sibility of the participation of dehydroascorbic acid as a co-enzyme in oxidative metabolism of the hexahydroxydiphenoyl group to the corresponding dehydro group.