Stachyflin and acetylstachyflin, novel anti-influenza A virus substances, produced by Stachybotrys sp RF-7260 I.: Isolation, structure elucidation and biological activities

Two novel compounds, stachyflin and acetylstachyflin, have been isolated by solid-state fermentation of Stachybotrys sp. RF-7260. The structures of both metabolites, determined by detailed NMR analyses and X-ray crystallographic analysis, are novel with a pentacyclic moiety including cis-fused decalin. The absolute stereochemistry of stachyflins was determined by circular dichroism analysis. Stachyflin showed antiviral activity against influenza A virus (H1N1) in vitro with an IC50 value of 0.003 mum. Acetylstachyflin was about 77-fold less active than stachyflin.