Preparation and Antioxidant Activities in Vitro of Two Cu (II) Complexes Containing Flavonoid Compounds

Two copper complexes containing Genistein and Kaempferol had been prepared according to the previously reported methods for study on the effect of the synergistic interaction between flavonoid compounds and copper ion on their antioxidant activity. The structure of the complexes was characterized by elemental analysis, complexometric titration, IR spectroscopy, Electronic absorption spectroscopy and TG, and then the antioxidant activities for the complexes were determined by the photoreduction of nitroblue tetrazolium (NBT) and salicylic acid method. The results suggested that the hydroxyl and carbonyl O atoms at A-ring and C-ring were coordinated to Cu (II) ion bidentately, the molar ratios between flavonoid compounds and Cu (II) were both 2:1, the possible formulae were as follows:Cu (Gen) ₂ (H₂O) ₂·3H₂O (1) andCu (Kae) ₂ (H₂O) ₂·1.5H₂O (2). The complexes exhibited the excellent scavenging ability for O₂^-·with IC₅₀ values of 0.250 and 0.646 μmol/L, respectively, in which Cu (II) played a vital role. The IC₅₀ values of complexes 1 and 2 for scavenging OH·were 158 and 129 μmol/L, respectively, in which the flavonoid compounds were crucial. Therefore, the complexes showed the positive synergistic effect between the flavonoid compounds and Cu (II) ion on the scavenging ability of O₂^-·and OH·.