Selective Cytotoxicity of Portuguese Propolis Ethyl Acetate Fraction towards Renal Cancer Cells

Renal cell carcinoma is the most lethal cancer of the urological system due to late diagnosis and treatment resistance. Propolis, a beehive product, is a valuable natural source of compounds with bioactivities and may be a beneficial addition to current anticancer treatments. A Portuguese propolis sample, its fractions (n-hexane, ethyl acetate, n-butanol and water) and three subfractions (P1–P3), were tested for their toxicity on A498, 786-O and Caki-2 renal cell carcinoma cell lines and the non-neoplastic HK2 kidney cells. The ethyl acetate fraction showed the strongest toxicity against A498 (IC(50) = 0.162 µg mL(−1)) and 786-O (IC(50) = 0.271 µg mL(−1)) cells. With similar toxicity against 786-O, P1 (IC(50) = 3.8 µg mL(−1)) and P3 (IC(50) = 3.1 µg mL(−1)) exhibited greater effect when combined (IC(50) = 2.5 µg mL(−1)). Results support the potential of propolis and its constituents as promising coadjuvants in renal cell carcinoma treatment.