Dammarane-type triterpene glycosides from Oncoba manii active against methicillin-resistant Staphylococcus aureus.

Drug-resistant bacteria are becoming more prevalent both in the community and in hospitals. In a search for new antibiotic leads, we used a high-throughput natural products chemistry approach to isolate one new (1) and two known (2, 3) dammarane-type triterpenes with mass-limited material from the African plant Oncoba manii. The new compound was determined by spectroscopic methods to be 1beta,2alpha,3beta,20(R)-tetrahydroxydammar-24-ene 3-O-alpha-L-rhamnopyranosyl-(1 --> 2)-beta-D-glucopyranoside. Compounds 1 and 2 inhibited the growth of methicillin-resistant Staphylococcus aureus (MRSA).