Tannins and related polyphenols of euphorbiaceous plants. XIV. Euphorbin I, a new dimeric hydrolyzable tannin from Euphorbia watanabei

Abstract

A new dimeric dehydroellagitannin, euphorhin I (3), was isolated together with twenty-eight known polyphenols including dimeric ellagitannins, euphorhins A (1) and B (2), from the fresh leaves of Euphoria watanabei. The structure of 3 which has a macaranoyl group as a linking unit between the monomers was established based on spectroscopic methods and chemical correlation with 1. The structure of euphorbin B (2c), previously assigned as a dimer having the valoneoyl group as the linking unit, was revised to 2 having a tergalloyl group.