New Squalene Triterpenes From the Fungus <i>Irpex laceratus</i>

Six undescribed squalene triterpenes, named irpelacerins A-F (1-6), together with three known lanostane triterpenoids (7-9) were isolated from the solid fermentation of the endophytic fungus Irpex laceratus, which was collected from the medicinal plant Casuarina equisetifolia L. Compounds 1-6 were a group of uncommon chain triterpenoids, which existed in the form of acyclic or monocyclic structures. Their chemical structures were determined by extensive analyses of NMR spectroscopic data, high-resolution electrospray ionization mass spectrometry, and comparison with literature analogs. Moreover, all these compounds were evaluated for their biological activities, and the results clarified that compounds 3, 6, 8, and 9 showed notable inhibitory activity against LPS-induced NO production with IC₅₀ values of 32.5, 48.0, 76.8, and 58.8 µM, respectively.