Tannins and Related Polyphenols of Melastomataceous Plants. II. Nobotanins B, C and E, Hydrolyzable Tannin Dimer and Trimers from Tibouchina Semidecandra COGN.

Abstract

The structures of three new hydrolyzable tannin oligomers, nobotanins B (7), C (20) and E (21), which were isolated from the leaves of Tibouchina semidecandra COGN. (Melastomataceae), have been elucidated on the basis of spectral and chemical evidence. Nobotanin B is an isomer of a co-existing dimer, nobotanin F, and nobotanins C and E are trimers possessing the nobotanin B moiety as a partial structure.