Calotropis gigantea (Linn) and Amoora rohituka (Roxb.) have long been used in folkloric medicine for the treatment of various ailments in Bangladesh. The present study was designed to investigate the cytotoxicity of isolated compounds from these two plants. Two compounds, named β-boswellic acid (compound-1) and 2-methoxy-14-calamenenone (compound-2) were isolated from the flowers of Calotropis gigantea and stem bark of Amoora rohituka, respectively. The structures of these compounds were confirmed on the basis of IR, Mass and NMR spectroscopy, and their cytotoxic activity against A431 (human vulval-derived epidermoid carcinoma) cell line was examined. When compared with standard drug doxorubicin (IC50: 0.31 ± 0.02 μg/mL), compound-1 exhibited significant cytotoxic activity against A431 cell line with IC50 value of 0.36 ± 0.07 μg/mL whereas the IC50 of compound-1 was 0.56 ± 0.05 (μg/mL). On comparison with ampicillin trihydrate (IC50: 7.21 ± 0.47 μg/mL), compound-1 also showed moderate cytotoxicity against brine shrimp nauplii with IC50 value of 15.26 ± 0.57 μg/mL.