Tannins and Related Compounds. LXXXIV. Isolation and Characterization of Five New Hydrolyzable Tannins from the Bark of Mallotus japonicus

Abstract

A chemical examination of the bark of Mallotus japonicus (thunb.) mueller-A rg. (Euphorbiaceae) has led to the isolation of five new hydrolyzable tannins (16—20), together with fourteen known tannins (1—14). On the basis of chemical and spectroscopic evidence, the structures of compounds 16 and 17 were established as l,2-di-0-galloyl-3,6-(/?)-hexahydroxydiphenoyl-^-D-glucose and l-0-digalloyl-3,6-(/?)-hexahydroxydiphenoyl-/?-D-glucose, respectively, while compounds 18 (mallojaponin) and 19 (mallonin) were shown to be l-0-galloyl-2,4-elaeocarpusinoyl-3,6-(J?)-valoneayl-/J-D-glucose and l-0-galloyI-2,4-elaeocarpusinoyI-/?-D-glucose. Compound 20 (mallotusinin) was characterized as a novel ellagitannin which possesses a unique l,l/-(3,3/,4,4/-tetrahydroxy)dibenzofurandicarboxyl group. On the other hand, examination of the leaves revealed the presence of hydrolyzable tannins (8—10, 12—15) all containing a 0-D-glucopyranose core with 1 C4-conformation. Furthermore, the orientation of the valoneayl group in mallotinic acid (13) and mallotusinic acid (14), which had remained unclarified, was determined on the basis of 1H-13C shift correlation spectral analysis and chemical correlations. © 1989, The Pharmaceutical Society of Japan. All rights reserved.