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

ABSTRACT: 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 µM (the IC(50) of positive control pyrrolidine dithiocarbamate was 20.0 µM). GRAPHICAL ABSTRACT: [Image: see text] SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s13659-022-00356-x.