Tannins and Related Polyphenols of Euphorbiaceous Plants. XIV. Euphorbin I, a New Dimeric Hydrolyzable Tannin from Euphorbia watanabei.

A new dimeric dehydroelalgitannin, euphorbin I (3), was isolated together with twenty-eight known polyphenols including dimeric ellagitannins, euphorbins A (1) and B (2), from the fresh leaves of Euphorbia 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...