Strategies for conventional cancer treatment including chemotherapy and radiation therapy decrease the bulk of tumor cells but a population of cancer stem cells (CSCs) remains. CSCs comprise a very small population in many cancers with ability of self-renewal and differentiation. Drug resistance of CSCs lead to their survival after treatment which finally result in cancer recurrence. It has been shown that many phytochemicals and plant extracts are able to target CSCs and may be a true therapeutic strategy for eradicating cancer. In this study, we evaluated the in vitro cytotoxic activity of methanol extracts of four medicinal plants against P19 embryonal carcinoma cell which is considered as a CSC. Trypan Blue exclusion assay and MTT assay were used for evaluation of plant extract cytotoxicity. Morus alba showed the highest cytotoxic effect on P19 cells which is followed by Eucalyptus camaldulensis and Zataria multiflora and the least cytotoxicity was found in Circhorium intybus. Although Morus alba methanol extract showed the most potent anti-proliferative activity and could be investigated for finding pure anticancer compounds, but IC50 values> 100 of mentioned plant extracts after 48, 96 and 144 h incubation period indicates their weak cytotoxicity against P19 cells.
Key words: Circhorium intybus, Zataria multiflora, Morus alba, Eucalyptus camaldulensis, Cytotoxicity, MTT, P19 cell line, Plant extract