A bioassay-guided study of Pulicaria gnaphalodes from the Asteraceae (Compositae) family led to the isolation of luteolin (1), quercetin (2), 4 – methoxy benzoic acid (3), and quercetin-3-O-b-D-glucuronide (4). Their structures were recognized based on spectroscopic analyses. The cytotoxicity of methanol extract of aerial parts and five fractions (n-hexane, CHCl3, EtOAc, n-BuOH, and H2O) of the plant was tested against MCF-7 and DU- 145 by MTT assay. Also, the ability of extract and fractions to act as free radical scavengers were measured by DPPH radical scavenging assay. As a result, the EtOAc fraction was selected for phytochemical analysis based on the half-maximal inhibitory concentration (IC50 ¼ 107.99 ± 2.89 mg/ml) and antioxidant activity (IC50 ¼ 10.64 ± 1.45 mg/ml). Finally, three flavonoid compounds 1, 2, 4, and one phenolic compound 3 were isolated from the EtOAc fraction and all isolated compounds were tested for their cytotoxicity. Both compounds 1 and 2 exhibited remarkable inhibitory activity on MCF-7 and DU-145 cell lines. Regarded to the above results, it could be concluded that Pulicaria gnaphalodes can be considered a natural source of biological compounds for further research.
