Background & aim: Stachys pilifera Benth (Lamiaceae) is used in traditional medicine to treat a variety of diseases. Despite some reports on the antitumor effects of some species of this genus, anticancer activity of Stachys pilifera has not been yet reported. In the present study, the researchers examined the cytotoxic effect and cell death mechanisms of methanolic extract of Stachys pilifera and its alkaloid and terpenoid fractions on the HT-29 colorectal cell line.

Methods: In the present study, HT-29 cells were cultivated and afterwards incubated in the methanolic extract of Stachys pilifera and its fractions at various concentrations for 24 hours. Cell viability was measured by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. The effects of the extract and the tests performed on cell death mechanisms such as fragmentation of DNA and apoptosis were performed by flow cytometry. Cisplatin was used as the positive control. The collected data was analyzed by ANOVA and Tukey test.

Results: The results of IC50 of methanolic extract, alkaloid, tropenoid, and cisplatin on HT-29 cells after 24 hours were 612.8, 46.4, 46.8 and 4.06 μg / ml, respectively. The results indicated that the inhibition of cell proliferation was dose-dependent. The methanolic extracts of Stachys and cisplatin resulted in DNA fragmentation. The results of apoptosis test revealed that the highest percentage of apoptosis was observed in cisplatin (30.8%) and methanolic extracts (23.2%) than the control (untreated) group (P <0.05).

Conclusion: These findings provide a basis for the therapeutic potential of S. pilfera in the treatment of colon cancer.