Tetra-, penta-, and hexa-nor-lanostane triterpenes from the medicinal fungus Ganoderma australe

Chemical investigation on the medicinal fungus Ganoderma australe led to the identification of ten new nor-lanostane triterpenes, namely two hexa-nor ones, ganoaustratetraenones A ( 1 ) and B ( 2 ), five penta-nor ones, ganoaustraldehydes A–E ( 3 – 7 ), and three tetra-nor ones ganoaustrenoic acids A–C ( 8 – 10 ). The chemical structures along with the absolute configurations were determined by extensive spectroscopic analysis of 1D & 2D NMR and HRESIMS data. The postulated biosynthesis pathways of these compounds were proposed. Ganoaustraldehydes A ( 3 ) and B ( 4 ) showed moderate inhibition against nitric oxide production in RAW264.7 macrophage cells with the respective IC 50 values of 32.5, 34.2 µ M (the IC 50 of positive control pyrrolidine dithiocarbamate was 20.0 µ M). Graphical Abstract