Acrocalysterols A and B, two new steroids from endophytic fungus Acrocalymma sp

Two new steroids, named acrocalysterols A (1) and B (2), together with five known compounds were isolated and characterized from an endophytic fungus Acrocalymma sp., isolated from the tender stems of Sinomenium acutum. The structures of the isolated metabolites were identified based on UV, IR NMR (1D and 2D), HR-ESI-TOF-MS, single-crystal X-ray diffraction experiment using Cu K alpha radiation and CD spectra associated with TD-DFT calculation. The bioassay showed that compound 2 displayed potent cytotoxicity against three cancer cell lines HeLa, HCC-1806, and RKO with IC50 values ranging from 18.37 to 19.64 mu M.