Sesquiterpenoids with PTP1B Inhibitory Activity and Cytotoxicity from the Edible Mushroom Pleurotus citrinopileatus

One new perhydrobenzannulated 5,5-spiroketal sesquiterpene, pleurospiroketal F (1), as well as six new modified bisabolene sesquiterpenes pleurotins A–F (2–7) were isolated from solid-state fermentation of Pleurotus citrinopileatus. The structures of compounds 1–7 were determined by NMR and MS spectroscopic analysis. The absolute configuration of 1 was determined by X-ray diffraction analysis, while the absolute configurations of 3–7 were assigned using the in situ dimolybdenum circular dichroism method and circular dichroism data comparison. Protein tyrosine phosphatase 1B plays a crucial role as a negative regulator of the insulin-dependent signal cascades. Therefore, the protein tyrosine phosphatase 1B inhibitor can be used for treating type 2 diabetes mellitus and obesity. Compounds 2 and 6 showed moderate inhibitory effects on protein tyrosine phosphatase 1B with IC50 s of 32.1 µM and 30.5 µM, respectively. The kinetic study confirmed compound 2 to be a noncompetitive inhibitor. Compounds 1–7 did not show cytotoxic activity against cancer cell lines (IC50 > 50 µM).