Ring B aromatic steroids from an endophytic fungus, Colletotrichum sp.

Abstract

The new (22E,24R)-3-acetoxy-19(10→6)-abeo-ergosta-5,7,9,22-tetraen- 3β-ol (1) and the known (22E,24R)-19(10→6)-abeoergosta-5,7,9,22- tetraen-3β-ol (2), two interesting ergosteroids with rare aromatized ring B, together with seven known derivatives, namely (22E,24R)-ergosta-5,7,22-trien- 3β-ol (3), (22E,24R)-ergosta-4,7, 22-trien-3-one (4), (22E,24R)-ergosta-4, 6,8(14),22-tetraen-3-one (5), (22E,24R)-5α,8α-epidioxyergosta-6,22- dien-3β-ol (6), (22E,24R)-ergosta-7,22-dien-3β,5α,6β-triol (7), (22E,24R)-6-acetoxy-ergosta-7,22-dien-3β,5α,6β-triol (8), and (22E,24R)-3,6-diacetoxy-ergosta-7,22-dien-3β,5α,6β-triol (9), were isolated from Colletotrichum sp., an endophytic fungus isolated from Ilex canariensis from Gomera. The structures of these compounds were elucidated by detailed spectroscopic analysis, comparison with reported data, and chemical interconversion. The isolation of these metabolites not only displays a beautiful array of chemical diversity, but also gives insight into the biosynthetic interconnections. Preliminary studies showed antimicrobial activity of these compounds against the fungus Microbotryum violaceum, the alga Chlorella fusca, and the bacteria Escherichia coli and Bacillus megaterium.