Sterostreins F-O, illudalanes and norilludalanes from cultures of the Basidiomycete Stereum ostrea BCC 22955

► Ten illudalane and norilludalane triterpenoids were isolated from cultures of Stereum ostrea BCC 22955. ► Their structures were elucidated on the basis of NMR spectroscopic and mass spectrometry data. ► Sterostreins M, N, and O are pyridine-containing illudalanes.