Direct current polarographic (DCP) antioxidant assay based on the decrease of anodic limiting current of HydroxoPerhydroxoMercury(II) Complex [Hg(O2H)(OH)] (HPMC) upon addition of antioxidants (AOs) was verified. Here, influence of several common AOs on DCP cathodic currents of both HPMC and Hg2+ was followed. Amperometric titrations of HPMC and Hg2+ with AOs and potentiometric titrations of Hg2+ were performed. The changes of DCP i-E curves and limiting currents decrease during amperometric titrations, as well as end points of amperometric and potentiometric titrations for each AO used as titrant proved the occurrence of Hg2+ reduction, either from complex (HPMC) or salt (HgCl2) solution. Constant H2O2 reduction current during amperometric titration of HPMC further confirmed the participation of Hg2+ as the oxidant species in reaction with AOs. The possibility of determining AO activity of flavonoids, phenolic acids, ascorbic acid and Trolox based on the decrease of Hg2+ reduction current was demonstrated. Strict correlation (R-2 = 0.96) between a new AO assay named MRAP (Mercury Reduction Antioxidant Power) and HPMC assay was found. Total AO capacity of real samples was measured by the proposed fast, simple and inexpensive MRAP assay as well. (C) 2015 Elsevier Ltd. All rights reserved.