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The microbial transformation of leucosceptrine ( 1 ), the first member of class leucosesterterpenes, by Rhizopus stolonifer afforded two metabolites, 1α-hydroxyleucosceptrine ( 2 ), and 8α-hydroxyleucosceptrine ( 3 ).

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.

Part of tre work was carried out under the H.E.J. Institute Karachi-University of Sussex Link Scheme. We thank Professor Atta-ur-Rahman. Dr. D.R.M. Walton and the British Council for establishing this link. We also thank the Spanish Ministry of Education for a grant.

Incubation of methyl ent-15-oxokaur-16-en-19-oate with Rhizopus stolonifer and Mucor plumbeus gave methyl ent-7β,11α-dihydroxy-15-oxokauran-19-oate and methyl ent-7β,16β-dihydroxy-15-oxokauran-19-oate, respectively.

Microbial transformation of ent-kaur-16-en-19-oic acid was carried out with R. stolonifer. After seven days of incubation, two metabolites, ent-7 alpha-hydroxy-kaur-16-en-19-oic acid and ent-12 beta-hydroxy-kaur-9(11),16-dien-19-oic acid, were isolated as a result of hydroxylation and hydroxylation/dehydrogenation, respectively. Incubation for 15 days also afforded ent-16 beta,17-dihydroxy-kauran-19-oic acid. The metabolites were identified by spectroscopic methods.