Microbial transformation of oral contraceptive ethisterone by Aspergillus niger and Cunninghamella blakesleeana.

Ethisterone (17α-ethynyl-17β-hydroxyandrost-4-en-3-one) (1) is a synthetic steroidal estrogen. It is extensively used as an oral contraceptive. The current study involves the structural transformation of ethisterone (1) by Aspergillus niger, and Cunninghamella blakesleeana. Fermentation of 1 with C. blakesleeana afforded two new polar metabolites, 17α-ethynyl-6β,15β,17β-trihydroxyandrost-4-en-3-one, and 17α-ethynyl-7β,15β,17β-trihydroxyandrost-4-en-3-one, while transformation of ethisterone with A. niger yielded a new metabolite, 17α-ethynyl-6α,17β-dihydroxyandrost-4-en-3-one, along with a known metabolite, 17α-ethynyl-11α,17β-dihydroxyandrost-4-en-3-one. Modern spectroscopic techniques were used to characterize the structures of all transformed products.