Isolation of C-29 oxygenated oleanane triterpenoids and a (+)-muurolene type sesquiterpenoid from the fruiting bodies of Fuscoporia torulosa and their bioactivities

Basidiomycetes with a wide variety of skeletons of secondary metabolites can be expected to be the source of new interesting biological compounds. During our research on basidiomycetes, two new C-29 oxygenated oleanane-type triterpenes (1 and 2) and torulosacid (3), a muurolene type sesquiterpenoid with a five-membered ether ring along with nine known compounds (4–12), were isolated from the MeOH extract of the fruiting bodies of Fuscoporia torulosa. The structures of 1–3 were determined by NMR and HREIMS analysis. Further studies on the stereochemistry of 3 were conducted using X-ray crystallographic analysis and comparison of experimental and calculated ECD spectra. In the antimicrobial assay of isolates, 1, 7, and 9 showed growth inhibitory activity against methicillin-resistant Staphylococcus aureus and other gram-positive strains. Isolation of oleanane type triterpenes from fungi including basidiomycetes, is a unique report that could lead to further isolation of new compounds and the discovery of unique biosynthetic enzymes.