Background and Objective: Plant polyphenols are natural sources of antioxidants that can help prevent many diseases, including cancer. Silymarin (SLM) and Ellagic acid (ELG) are two natural polyphenols, and in this study, for the first time, their cytotoxic effects and antioxidant activity were investigated individually and in combination in breast cancer cells.

Methods: The cytotoxicity of Silymarin and Ellagic acid, alone and in combination, was investigated in the 4T1 breast cancer cell line using the MTT assay. Their antioxidant activity was also evaluated through the Ferric Reducing Antioxidant Power (FRAP) and 2,2-diphenyl-1-picrylhydrazyl (DPPH) methods, both alone and in combination.

Results: The findings revealed that Ellagic acid resulted in a more significant reduction in cell growth compared to Silymarin. The combined application of Silymarin and Ellagic acid demonstrated superior efficacy in inhibiting cancer cell proliferation compared to either compound used alone. Silymarin exhibited more antioxidant activity in the FRAP assay than Ellagic acid, while Ellagic acid outperformed Silymarin in the DPPH assay. Notably, the combination of these two substances enhanced antioxidant properties in both tests, particularly at molar ratios of 8:1 (p < 0.001) and
4:1(p < 0.05), as well as 50:6.25 and 50:12.5 SLM: ELG, indicating significant synergistic inhibitory effects.

Conclusion: The results underscore Silymarin and Ellagic acid's cytotoxic effects and antioxidant activity. Furthermore, their combined use leads to a synergistic effect, suggesting that this combination treatment could represent a promising candidate for further research in breast cancer studies.