The microbial transformation of racemic diisophorone was investigated using the plant pathogen Aspergillus niger as a biocatalyst. Incubation of diisophorone with Aspergillus niger gave 8alpha-hydroxydiisophorone, 10-hydroxydiisophorone and 17-hydroxydiisophorone on the basis of their spectroscopic data including two-dimensional NMR analysis, nOe and an X-ray crystallographic study. The antifungal activity of diisophorone against Aspergillus niger was also examined. (C) 2004 Society of Chemical Industry