Polyaniline tannate (PANI-TA) solid microspheres were synthesized by the external-template-free oxidative polymerization of aniline with ammonium peroxydisulfate (APS) in aqueous solution of tannic acid (TA). Syntheses were performed using fixed mole ratio [TA]/[aniline] and varying [APS]/[aniline] mole ratios and polymerization times. PANI-TA materials were characterized by scanning and transmission electron microscopies, FTIR and Raman spectroscopies, elemental microanalysis and conductivity measurements, and their structure and properties were compared. The ability of PANI-TA microspheres to act as antioxidants was investigated by cyclic voltammetry using the electrocatalytical reduction of O-2 to the superoxide anion radical (O-center dot(2)-) and analyzing the evolution of the electrochemical response upon successive addition of PANI-TA as a radical scavenger. All synthesized materials showed very good O-center dot(2)- scavenging activity. It was shown that the scavenging activity of PANI-TA can be tuned by the conditions of its synthesis, thus leading to the material showing higher antioxidant activity than pure TA. Observed differences in radical scavenging activities of PANI-TA materials were discussed. (C) 2014 Published by Elsevier Ltd.