Cytotoxicity and redox-associated responses to the methanolic fraction of Ocimum sanctum in MCF-7 breast cancer cells

Plant-derived preparations continue to attract interest as sources of bioactive molecules with potential relevance to cancer research. Ocimum sanctum has been investigated for antioxidant, cytotoxic, and pharmacological activities, but the cellular responses associated with its solvent fractions require further characterization. Because cellular redox balance is closely linked to survival and stress adaptation, examining redox-associated responses alongside cytotoxicity may provide useful preliminary information on the biological activity of plant fractions. This study investigated the cytotoxic effects and redox-associated biochemical responses to the methanolic fraction of Ocimum sanctum leaves (OSMF) in MCF-7 human breast cancer cells. The cytotoxic effects of hexane (OSHF), ethyl acetate (OSEAF), and methanolic (OSMF) fractions of Ocimum sanctum leaves were assessed using the WST-8 assay. Apparent IC 50 values were estimated from concentration-response curves. OSMF produced the strongest reduction in WST-8 metabolic signal among the tested fractions and was used for the subsequent experiments. MCF-7 cells were exposed to 50% and 100% of the apparent OSMF IC 50 for 24 and 48 h. Malondialdehyde (MDA), reduced glutathione (GSH), superoxide dismutase (SOD), catalase (CAT), glutathione S-transferase (GST), glutathione peroxidase (GPx), and nitric oxide-associated responses were determined using biochemical assays. Cellular morphology was examined microscopically. Putative constituents of OSMF were characterized by GC-MS using spectral-library matching. Assays were performed in triplicate; data were analyzed by ANOVA with Tukey’s post-hoc test. OSMF exhibited the greatest cytotoxic activity among the three fractions examined, although the apparent IC 50 was relatively high (736.7 µg/mL) and the highest-dose WST-8 response was non-monotonic. OSMF exposure was associated with reduced MDA and increased GSH, SOD, CAT, GST, and GPx values relative to untreated cells. Nitrite-associated NO levels showed a more limited response, with the clearest increase observed at one treatment condition. Treated cells displayed shrinkage, rounding, membrane blebbing, and detachment, consistent with apoptotic-like morphological changes. GC-MS analysis identified several putative constituents, including 2, 4-di-tert-butylphenol and dodecane, 2, 6, 10-trimethyl-. OSMF produced cytotoxic/metabolic effects in MCF-7 cells and was associated with changes in redox-related biochemical parameters and apoptotic-like morphology. The present findings do not establish direct ROS generation, iNOS-dependent signalling, or molecularly confirmed apoptosis. Direct ROS measurements, molecular cell-death markers, orthogonal viability assays, and studies in non-tumorigenic breast cells are required to define the mechanism and selectivity of the observed response.