Abstract
This communication describes the in situ combination of Al(III) and Zn(II) with resveratrol, and evaluation of the antioxidant power of the novel species via DPPH• assay. The formation of the complexes in aqueous medium was verified by Job's method, using fluorescence spectroscopy. The metal / ligand stoichiometry for the Zn(II) / resveratrol complex was found to be 1:2 and, for the Al(III) / resveratrol complex two preferential species were formed with 1:1 and 3:1 stoichiometries. The compounds were also studied by 1H and 13C NMR spectroscopy. Their antioxidant activity, evaluated by a scavenging assay using DPPH• (1,1-diphenyl-2-picrylhydrazyl), demonstrated that the combined species are more effective free radical scavengers than free resveratrol. The electrochemical behavior of the complexes revealed the occurrence of irreversible oxidation processes, which take place at a lower potential than that observed with free resveratrol. These results indicate that metallic complexes of this natural product have a higher antioxidant power than resveratrol alone.