Antimicrobial activity of kaurenoic acid derivatives substituted on carbon-15.

The antibacterial and antifungic activities of two kaurenic acids, ent kaurenoic acid and cinnamoylgrandifloric acid isolated from a hexane extract of aerial parts of Mikania laevigata, were investigated and compared with the activities of other kaurenic acid derivatives substituted on carbon-15. Only acetylgrandifloric acid (ent-kaur-16-en-15 alpha-acetyloxy-19-oic) and its epimer xylopic acid (ent-kaur-16-en-15 beta-acetyloxy-19-oic) displayed significant antibacterial activity at concentrations greater than or equal to 250 micrograms/ml, the 15 alpha epimer being the most active.