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Based on the chromatographic survey which revealed wide distribution of dehydroellagitannins, geraniin (1) and mallotusinic acid (2), in Euphorbia, Mallotus, Aleurites, Sapium and Phyllanthus species of Euphorbiaceous plants, and also on the isolation of euphorbins A (3) and B (4), dimeric hydrolysable tannins, having the geraniin structure as a part of their molecules, from Euphorbia hirta, a further search of oligomers of novel structural units was carried out. Three new dimers, euphorbins C (5), D (6) and E (21) were isolated from the same plant and their structures were elucidated. Euphorbins C and D are dimers of new class which possess, in addition to the geraniin structure in their molecules as in 3 and 4, a unique new tetrameric galloyl (euphorbinoyl) group which is biogenetically regarded as the product of C-O oxidative couplings between two galloyl groups in a monomer and hexahydroxydiphenoyl group in the another monomer. Euphorbin E is the first example of the dimeric hydrolyzable tannins having a dehydroeuphorbinoyl group as a linking unit between two monomers. Euphorbin A (3) and an analogous new dimer, euphorbin F were also isolated from E. tirucallii, the latter of which was found to have structure (26). E. prostrata was found to contain a different type of hydrolyzable tannin oligomers, rugosins D (27), E (28) (dimers) and G (29) (trimer).
