Variation of the antimicrobial activity of Pseudognaphalium vira vira (Asteraceae): isolation and X-ray structure of ent-3 beta-hydroxy-16-kauren-19-oic acid

The antimicrobial properties of the resinous exudate from twigs and leaves of a population of Pseudonaphalium vira vira were re-examined against five Gram positive bacteria. The observed decrease in the antimicrobial activity might reflect a change in the diterponoid composition of the exudate. The title compound 2 was isolated in substantial amount, together with ent-16-k auren-19-oic acid (I), and its structure determined by X-ray diffraction an alysis. (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.