Preparation, Characterization and Antioxidant Evaluation of Cu(II) and Zn(II) Tannates

The interest in the antioxidant materials increased due to their free radical scavenging properties avoiding various pathologies. Tannic Acid (TA) is known to have high free radical scavenging activity, but its application is still limited. This paper had the objective of synthesis, characterization and evaluation of free radical scavenging activity of TA associated with Cu (II) and Zn (II) ions, in a buffered aqueous medium. Techniques of FTIR, simultaneous TG-DSC characterized the obtained compounds, and the evaluation of free radical scavenging activity was made using 2,2–diphenyl–1–picrylhydrazyl (DPPH) radical. The FTIR analysis of the compounds showed significant displacement of the main bands in the TA spectrum (νC=O, δO-H, σO-H), suggesting an association of metal ions with the oxygen of the hydroxyl group of TA. TG-DSC curves showed information about the thermal stability, stoichiometry, hydration water, and residues formation. The TA association with the metal ions Cu(II) and Zn(II) decreased the antioxidant activity of the molecule significantly, showing that these compounds could be potentially used as pro-oxidant agents.