Background and purpose: Papaver rhoeas L (family: Papaveraceae) is commonly known as corn poppy. Recent studies have revealed that Papaver rhoeas L extract has cytotoxic, genotoxic, and antioxidant effects. The present study aimed at evaluating the cytotoxic effect and antioxidant activity of Papaver rhoeas L. methanolic extract on monkey kidney carcinoma cell lines (Vero).

Materials and methods: Methanolic extract of Papaver rhoeas L. was prepared by maceration method. Cultivated cell line Vero was incubated with different concentrations (0, 10, 50, 100, 500, and 1000µg/ml) of the extract for 72 hours and cell growth inhibition was determined using MTT assay. The antioxidant capacity was assessed using two methods: DPPH and ferric reducing ability of plasma (FRAP). The total phenolic and flavonoid contents were also determined.

Results: The IC50 of cisplatin, as a common drug, is significantly lower than that of the Papaver rhoeas L. (IC50= 15.96±0.26 μg/ml). Our results showed that Papaver rhoeas L. extract caused a significant decrease in proliferation in monkey kidney cancer cell line (IC50=80.07 μg/ml). The scavenging effect of the extract on DPPH^• radical was found to be 5.74 μg/ml. The extract’s ferric reducing ability of plasma was 2.663 ± 0.002 μg/ml. Also, the extract had more total phenolic content rather than flavonoid contents.

Conclusion: This study showed that methanolic extract of Papaver rhoeas L. has potent cytotoxic effect on cancer cell line Vero and considerable antioxidant activity. But further investigations are required to identify efficient compounds and molecular mechanism of this extract so that effective steps could be taken towards finding new drugs in treatment of diseases.