Vibralactone D

Extracts obtained from liquid mycelial fermentations of the Chilean fungus Stereum hirsutum (Sh134-11) showed antifungal activity against Botrytis cinerea. Two types of extracts were obtained: EtOAc-extract (liquid phase) and MeOH-extract (mycelial phase). Plate diffusion assay showed that EtOAc-extracts were more active than MeOH-extracts. A large-scale fermentation of Sh134-11 and chromatographic methods allowed to isolated four compounds: MS-3, Vibralactone, Vibralactone B and Sterenin D. Only Sterenin D showed antifungal activity against B. cinerea in the tests performed. Effects on the mycelial growth of B. cinerea showed that Sterenin D showed inhibition at 1000-2000 μg/mL reaching 67% and 76% respectively. Sterenin D was more effective to control the sporogenesis, inhibiting in 96% the sporulation at 500 μg/mL. Assays showed that Sterenin D exhibited a minimal fungicidal concentration (MFC) of 50 μg/mL and minimal inhibitory concentration (MIC) at 20 μg/mL. Our study indicated that submerged fermentations of Chilean S. hirsutum (Sh134-11) produced extracts with antifungal activity and Sterenin D is responsible for this activity, which could be used as possible biofungicides alternative to synthetic fungicides.

Three new metabolites, vibralactones D-F (1-3) were isolated from cultures of the basidiomycete Boreostereum vibrans. The relative configuration of 1 was established on the basis of X-ray diffraction analysis, while the absolute configurations of 1-3 were assigned using a modified Mosher's method. Compound 1 showed weak inhibitory activities against isozymes of 11beta-hydroxysteroid dehydrogenases (HSD) with IC(50) values of 85.7 microM (human HSD1), 295.2 microM (mouse HSD1), and 87.1 microM (human HSD2).