Tannins and Related Polyphenols of Melastomataceous Plants. III. Nobotanins G, H and I, Dimeric Hydrolyzable Tannins from Heterocentron roseum.

Abstract

Three new hydrolyzable tannin dimers, nobotanins G (6), H (12) and I (13), have been isolated from the leaves of Heterocentron roseum (Melastomataceae), and their structures were elucidated on the basis of chemical degradations and nuclear magnetic resonance spectral analyses. Nobotanin I (13) is a novel dimer possessing a depsidone-forming valoneoyl group in the molecule. Five known tannins, casuarictin (1), strictinin (2), geraniin (3), and nobotanins B (4) and F (5), were also isolated.