Abstract
Stachys pilifera (S. 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 S. pilifera has not been yet reported. Here, we examined the cytotoxic effect and cell death mechanisms of methanolic extract of S. pilifera and its alkaloid and terpenoid fractions on the HT-29 colorectal cell line. HT-29 cells were cultivated and then incubated in the methanolic extract of S. pilifera and its fractions at various concentrations for 24 h. Cell viability was measured by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Morphology of cells was evaluated by contrast microscopy. Furthermore, effects of the tested extract and fractions were tested on some regulators of cell death and proliferation such as caspase-8, caspase-9, nuclear factor-κB (NF-κB), and nitric oxide (NO). Cisplatin was used as positive control. The estimated IC(50) values of the methanolic extract, alkaloid and terpenoid fractions, and cisplatin against HT29 cell after 24 h were determined to be 612, 48.12, 46.44, and 4.02 μg/mL, respectively. Morphological changes such as plasma membrane blebbing, cell size reduction, and apoptotic bodies were observed in cells faced with the extract and fractions. S. pilifera extract and its fractions induced apoptosis through inhibition of NF-κB, NO, and activation of caspase-8 and caspase-9. Data showed considerable cytotoxic and antiproliferative effects of S. plifera on colorectal cell line through induction of apoptosis. These findings provide a basis for the therapeutic potential of S. pilfera in the treatment of colon cancer.