Four in vitro activities of apigenin to human colorectal carcinoma cells susceptible to air-oxidative and heating treatments

Flavonoids as the important natural phytochemicals have been widely assessed for their healthcare functions in recent years. Apigenin, one member of the flavonoid family, was dissolved in aqueous solution, and subjected to respective air-oxidative and heating treatments in this study to result in partial apigenin degradation. Impacts of the two treatments on apigenin's four in vitro activities to a human colorectal carcinoma line (HCT-116 cells) were assessed, in terms of growth inhibition, apoptosis induction, mitochondrial membrane potential (MMP) loss, and generation of intracellular reactive oxygen species (ROS). The results indicated that apigenin in dose-time-dependent manner inhibited the growth of the cells, and showed stronger anti-proliferation at 160 mmol/L than the air-oxidized or heated apigenin (67.4% versus 65.1% or 50.1%) at same dose level. Apigenin was also more powerful than the air-oxidized or heated apigenin to cause the cells with death morphology and MMP loss. In comparison with the air-oxidized or heated apigenin, apigenin at 160 mmol/L conferred the treated cells with more apoptotic cells (29.3% versus 28.3% or 8.3%) and much enhancement of the intracellular ROS (300.7% versus 247.3% or 201.7%), demonstrating that the treated apigenin had weaker apoptosis induction and pro-oxidation than the untreated apigenin. It is thus concluded that the four anti-cancer properties of apigenin in terms of anti-proliferation, MMP loss, death or apoptosis induction, and pro-oxidation were all susceptible to (i.e. weakened by) the air-oxidative and especially heating treatments.