Inhibition of fungal and mammalian sterol biosynthesis by 2-aza-2,3-dihydrosqualene.

2-Aza-2,3-dihydrosqualene (I) and a quaternary ammonium derivative (II) inhibited ergosterol biosynthesis in cells and cell-free extracts of the pathogenic yeast Candida albicans as measured by incorporation of radiolabelled precursors. The compounds inhibited squalene epoxidase and 2,3-oxidosqualene cyclase to varying degrees in microsomes from C. albicans and from rat liver. The rat liver epoxidase was 50% inhibited by I at 2.4 microM. In C. albicans cells, but not in cell-free extracts, I also inhibited lanosterol demethylation and led to accumulation of an unidentified polar product.