Metabolism of androst-4-en-3,17-dione by the filamentous fungus Neurospora crassa

Microbial transformation of androst-4-en-3,17-dione (AD; I) using Neurospora crassa afforded six metabolites; 6β,14α-dihydroxyandrost-4-en-3,17-dione (II), 6β,9α-dihydroxyandrost-4-en-3,17-dione (III), 7α-hydroxyandrost-4-en-3,17-dione (IV), 9α-hydroxyandrost-4-en-3,17-dione (V), 14α-hydroxyandrost-4-en-3,17-dione (VI), and androst-4,6-dien-3,17-dione (VII). The steroid products were assigned by interpretation of their spectral data such as 1H NMR, 13C NMR, FTIR, and mass spectroscopy. The characteristic transformations observed were C-6β, C-7α, C-9α, C-14α hydroxylations, and C6-C7 dehydrogenation. The best fermentation condition was found to be 6-day incubation at 25 °C and pH value of 5.0-6.5 according to TLC profiles. Time course study showed the accumulation of V and VI from the third day and IV from the fourth day of the fermentation. Optimum concentration of the substrate, which gave maximum bioconversion efficiency, was 3.5 mM in one batch. Biotransformation was completely inhibited in a concentration above 7.0 mM.