Biotransformation of clerodane diterpenoids by Rhizopus stolonifer and antibacterial activity of resulting metabolites

Microbial transformation of clerodane lactone ( 1 ) by a plant pathogen fungus, Rhizopus stolonifer , resulted in the production of metabolites 3 and 4 . While incubation of clerodane methyl ester ( 2 ) by R. stolonifer yielded metabolites 5 – 8 . The structures of the transformed products were determined by the spectroscopic techniques and compounds 4 , 7 and 8 were found. The antibacterial activity of clerodane diterpenoids 1 and 2 and their metabolites 3 – 8 were also studied. The metabolites 3 – 7 showed moderate activities against both Gram-positive and Gram-negative organisms. While metabolite 8 showed a moderate activity against Gram-positive organisms and a good activity against Gram-negative organisms.