Most effective anticancer drugs normally generate considerable cytotoxicity in normal cells; therefore, the preferential activation of apoptosis in cancer cells and the reduction of toxicity in normal cells is a great challenge in cancer research. Natural products with selective anticancer properties used as complementary medicine can help to achieve this goal. The aim of the present study was to analyze the effect of the addition of bee products [propolis (PR) or royal jelly (RJ) or propolis and royal jelly (PR+RJ), 2-10%] to thyme (TH) and chestnut honeys (CH) on the differential anticancer properties, mainly the cytotoxic and pro-apoptotic effects, in normal and cancer hepatic cells. The cytotoxic effects of samples were analyzed using the MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay (0-250 mg/mL) and the effects on apoptosis were analyzed using cell cycle analysis, TdT-dUTP terminal nick-end labeling (TUNEL) assay, DR5 (Death Receptor 5) and BAX (BCL-2-Associated X) activation, and caspases 8, 9, and 3 activities. Both honey samples alone and honey mixtures had no or very little apoptotic effect on normal cells. Antioxidant honey mixtures enhanced the apoptotic capacity of the corresponding honey alone via both extrinsic and intrinsic pathways. Of all the samples, chestnut honey enriched with 10% royal jelly and 10% propolis (sample 14, CH+10RJ+10PR) showed the highest apoptotic effect on tumor liver cells. The enrichment of monofloral honey with bee products could be used together with conventional anticancer treatments as a dietary supplement without side effects. On the other hand, it could be included in the diet as a natural sweetener with high added value.
Keywords: antioxidant honey mixtures; apoptosis; bee products; cancer; cytotoxicity; honey; propolis; royal jelly.