fig3

Figure 3. The influence of quercetin on cytotoxic effect of curcumin in HL-60 cells. Cells were incubated with curcumin in concentration of 10 (A) or 20 μmol/L (B) and/or increased concentrations of quercetin for 20 h. Cytotoxicity was investigated by using propidium iodide staining and analyzed in flow cytometer. Interaction between investigated compounds was analyzed by Calcusyn software (C). Quercetin increased significantly the cytotoxic effect of curcumin at the concentrations of 20-100 μmol/L (A) and (B) but the interactions between these two compounds were mostly antagonistic. For most combinations, the value of the combination index (CI) was greater than 1 (C). However quercetin at concentrations of 5 μmol/L induced additive effect with 20 μmol/L of curcumin (CI = 1), (C) but the effect of this two compounds was not significant compared to curcumin alone. Values are means ± SEM, *P < 0.05, **P < 0.01, ***P < 0.001 vs. control; ^###P < 0.001 vs. Cur; ⁺⁺P < 0.01, ⁺⁺⁺P < 0.001 vs. appropriate Q group (Mann-Whitney test). Cur: curcumin; Q: quercetin; CI: combination index, × combination of investigated compounds