Bouvardin (C40H48N6O10) and deoxybouvardin (C40H48N6O9), both of which show high antitumor activity in the 3PS, B1, and KB systems, were isolated from the methanol extract of Bouvardia ternifolia (Rubiaceae). An x-ray study on bouvardin containing a methanol of crystallization (P212121, a=9.009 (3), b=12.623 (4), c=42.970 (19) Å, Z=4) and hydrolytic studies showed it to be Ia, a cyclic hexapeptide composed of two L-alanines, a D-alanine, and three modified N-methyl-L-tyrosines. The most unusual feature is a 14-membered ring formed by oxidative coupling of the phenolic oxygen of one tyrosine with a carbon ortho to the phenolic hydroxyl group of an adjacent tyrosine. Spectral comparison with bouvardin indicated deoxybouvardin to be Ib, identical with bouvardin except for the lack of a β-hydroxyl group on one of the tyrosines.
ASJC Scopus subject areas
- Colloid and Surface Chemistry