The effect of flavonoids on the reduction of cupric ions, the copper-driven Fenton reaction and copper-triggered haemolysis
Abstract
Flavonoids are considered beneficial, but they may exhibit pro-oxidative effects likely due to metal reducing properties. For the first time, 24 structurally related flavonoids were compared for copper reduction, and modulation of the copper-triggered Fenton reaction and lysis of erythrocytes.
The vast majority of flavonoids reduced cupric ions; their behaviour ranged from progressive gradual reduction through bell-shaped, neutral, to a blockade of spontaneous reduction. Similarly, different behaviours were observed with the Fenton reaction.
Flavone was the only flavonoid that potentiated copper-triggered haemolysis (155 +/- 81 % at twice the amount of Cu2+), while 18 flavonoids were at least partly protective in some concentrations. Only 5-hydroxyflavone did not reduce Cu2+ and behaved as an antioxidant in both assays (reduction of 60 +/- 10 % and 88 +/- 1%, respectively, at an equimolar ratio with Cu2+).
In conclusion, relatively subtle structural differences resulted in very different anti/prooxidant behaviour depending on the model.