Fungal transformation of dydrogesterone and inhibitory effect of its metabolites on the respiratory burst in human neutrophils.

The biotransformation of the synthetic hormone dydrogesterone (1) by a number of fungal strains - including Cephalosporium aphidicola, Rhizopus stolonifer, Cunninghamella elegans, and Fusarium lini - afforded ten different metabolites, compounds 2-11. From a structural point of view, these transformations involved a combination of hydroxylation, oxidation, reduction, and/or epoxidation. The pregnane-based metabolites 10 and 11 are new compounds. All the known compounds were obtained for the first time from 1 by fungal transformation. The metabolites 3, 5, and 8 showed more-potent respiratory-burst inhibitory activity than the substrate 1 in a neutrophil-based cellular assay (Table 3).