Phytochemical studies on the dichloromethane fraction of Pterospermum truncatolobatum collected in Lang Son province has led to the isolation and structural elucidation of four secondary metabolites, including one rare triterpene possessing E:B-friedo-hopane-type triterpenoid: simiarenol (1), two sterols: β-sitosterol (2), stigmasterol (3) and one sterol glycoside: stigmasterol glycoside (4). Their structures were identified by spectroscopic analyses. In addition, the structure of 1 was confirmed by X-ray crystallographic analysis. Furthermore, simiarenol (1) showed moderate cytotoxicity against three cancer cell lines such as Hep-G2, Lu-1, and MCF-7 with its IC50 values of 38.47 ± 2.68
48.37 ± 3.05 and 46.85 ± 3.6 g\mL, respectively. All four compounds were isolated from this plant for the first time.