New azasteroidal antifungal antibiotics from Geotrichum flavo-brunneum. II. Isolation and characterization.

A novel group of antibiotics, comprising microbiologically-active structurally-related factors A25822A, B, D, H, L, M and N, produced by culturing Geotrichum flavo-brunneum NRRL 3862 under submerged aerobic fermentation conditions was isolated by extraction. The individual factors were separated and purified by chromatography and crystallization. The major factor, A25822B, a 15-aza-24-methylene-D-homocholestadiene is a white crystalline compound, C25H45NO. The antibiotics are highly active against fungi and marginally active against bacteria.