New metabolites of drospirenone obtained in Mucorales fungi culture

Microbial transformation of 6,7,15,16-dimethylene-3-oxo-17-pregn-4-ene-2,17-carbo-lactone, the well-known contraceptive drospirenone (1), using fungal cells was carried out. Six fungal strains of different species of Order Mucorales were evaluated in this study, namely Absidia corymbifera BAFC 1072, Absidia corymbifera BAFC 1080, A. coerulea, Mucor plumbeus BAFC 2314, Rhizopus oryzae and Syncephalastrum racemosum. Four products were obtained by hydroxylation at C-11 and C-2 and epimerization at C-17 of drospirenone by A. corymbifera BAFC 1072, A. coerulea and S. racemosum. The structures were elucidated as 6β,7β,15β,16β-dimethylene-11α-hydroxy-3-oxo-l7α-pregn-4-en-21,17-carbolactone (2), 6β,7β,15β,16β-dimethylene-11α-hydroxy-3-oxo-l7β-pregn-4-en-21,17-carbolactone (3), 6β,7β,15β,16β-dimethylene-11β-hydroxy-3-oxo-l7α-pregn-4-en-21,17-carbolactone (4) and 6β,7β,15β,16β-dimethylene-2β-hydroxy-3-oxo-l7α-pregn-4-en-21,17-carbolactone (5), on the basis of extensive spectral data including 2D NMR spectroscopy and MS. Products 3, 4 and 5 were found to be new compounds. Several biotransformation parameters such as the employment of growing or resting cells, inoculum size, agitation speed, drospirenone concentration, temperature, pH and presence of co-solvent were seen to be important to the optimization of the process.