Synergistic Antiproliferative Effects of Garcinia cowa Ethyl-Acetate Fraction Combined with Paclitaxel in T47D Breast Cancer Cells

Breast cancer therapy is often faces drug resistance and chemotherapeutic side effects with agents, -such as paclitaxel. A combination approach with natural agents may enhance therapeutic efficacy and reduce toxicity. This study aimed to assess the cytotoxic activity of the ethyl acetate fraction of Garcinia cowa leaves (EAGCL) against T47D breast cancer cells and to quantify the synergistic interaction between EAGCL and paclitaxel. T47D cells were treated with various concentrations of the ethyl acetate fraction of Garcinia cowa leaves (EAGCL; 0.1–100 µg/mL) and paclitaxel (0.001–1 µg/mL), either individually or in combination. Viability was assessed using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. The IC50 was determined, and interactions were analysed using the Chou–Talalay method with CompuSyn software to obtain the Fraction Affected (Fa), Combination Index (CI), and Concentration Reduction Index. The IC50 of EAGCL and paclitaxel against T47D were 14.83 µg/mL and 0.014 µg/mL, respectively. The sub-IC50 combination (EAGCL 15–30 µg/mL + paclitaxel 0.00175 µg/mL) produced Fa 0.68–0.82 and CI 0.28–0.59, indicating moderate to strong synergism. Concentration (Dose) Reduction Index showed the potential for a 17-fold reduction in paclitaxel concentration in the optimal combination and a 3–4-fold reduction in EAGCL concentration. The combination of EAGCL with paclitaxel demonstrated significant synergism in vitro in T47D cells, suggesting the potential to reduce the paclitaxel concentration. Further studies are needed such as apoptosis assays, cell cycle analysis, and evaluation of apoptosis/survival-related protein expression—to confirm the mechanism of action and safety.