Evaluation of Cytotoxic Activity and Combination Index of Stem Bark Ethyl Acetate Extract of <I>Garcinia cowa</I> and Doxorubicin in T47D Cells

Breast cancer continues to be one of the major causes of cancer-related mortality worldwide, underscoring the need for therapeutic strategies that are both effective and less toxic. Natural products are increasingly explored as potential adjuvants to chemotherapy due to their diverse bioactive compounds. This study evaluated the cytotoxic effect of the stem bark ethyl acetate extract of Garcinia cowa (SBEAE-GC) on T47D breast cancer cells and its potential to enhance the activity of doxorubicin. The cytotoxicity of SBEAE-GC and doxorubicin, alone and in combination, was assessed using the MTT assay, with absorbance measured at 550 nm using a microplate reader. The half-maximal inhibitory concentration (IC50) values were calculated, and drug interaction was analyzed using the Chou–Talalay method to determine the Combination Index (CI). Both SBEAE-GC and doxorubicin exhibited concentration-dependent cytotoxic effects on T47D cells, with IC50 values of 38.71 µg/mL and 0.030 µg/mL, respectively. The combination treatment demonstrated synergistic cytotoxicity, indicated by a CI value of 0.9, suggesting that SBEAE-GC potentiates the effect of doxorubicin. The findings reveal that SBEAE-GC possesses notable cytotoxic activity and can synergistically enhance the effect of doxorubicin against T47D breast cancer cells, supporting its potential role as an adjuvant candidate in breast cancer therapy.