Characterization of phytoconstituents in the 70% methanolic extract of Cissus rotundifolia (Forssk.) Vahl. was performed using high-performance liquid chromatography coupled with electrospray ionization mass spectrometry. Furthermore, tandem mass spectrometry (MS/MS) was performed to assist in the structural elucidation of compounds. Twenty-seven compounds were identified. The identified compounds were four acids, sixteen phenolics, two steroidal saponins, two coumarins, two stilbenoids and one triterpene. Astragalin 1, β-amyrin 2 and 1β-hydroxy-kryptogenin-1-O-α-L-rhamnopyranosyl-(1→2)-α-L-arabinopyranoside 3 were isolated by column chromatography and their structures were identified by spectral analysis including 1D and 2D NMR. The plant extract and the isolated compounds 1-3 were evaluated for their radical scavenging activity. Compounds 1 and 2 showed significant activity relative to that of ascorbic acid as a standard. The cytotoxicity of the plant extract, the isolated compounds and the standard doxorubicin was evaluated using the three human tumor cell lines HT116, MCF-7 and PC-3. The plant extract exhibited significant cytotoxicity against MCF-7 while showing no activity against the other cell lines. The isolated compounds 1-3 showed no activity against the used cell lines. پرونده مقاله