Microbial conversion of pregnenolone by some filamentous fungi

Abstract

In this work, biotransformations of pregnenolone 1 by Ulocladium chartarum MRC 72584, Cladosporium sphaerospermum MRC 70266 and Cladosporium cladosporioides MRC 70282 have been reported. U. chartarum MRC 72584 only hydroxylated 1 at C-7β and hydroxylated 1 at either C-7β or C-14α, accompanied with a concurrent epoxidation from the β-face. The same fungus hydroxylated a small amount of 1 at both C-7 and C-14α, accompanied with a subsequent oxidation at C-7. 3β,14α-Dihydroxy-5β,6β-epoxypregnan-20-one 4 and 3β,7β-dihydroxy-5β,6β-epoxypregnan-20-one 5 obtained from the incubation of 1 with this fungus were determined as new metabolites. C. sphaerospermum MRC 70266 converted most of 1 into a 3-keto-4-ene steroid and independently hydroxylated it at C-6α, C-6β and C-7β. This fungus also hydroxylated 1 at C-7 and C-11α and then oxidized it at C-7. C. cladosporioides MRC 70282 converted almost half of 1 into a 3-keto-4-ene steroid. The same fungus reduced some of this 3-keto-4-ene steroid by a 5α-reductase activity while it hydroxylated the rest at C-6α and C-6β.