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[References: 18 tit.]

A review of studies which evaluate intensity and mechanisms affecting the antioxidant activity (AOA) of humic acids(HAs) was conducted. Based on colorimetric assessment of HAs, high antiradical activity (ARA) of AO has beendetected. The mechanism of this action is most likely related to the ability of HAs to act as free radical “traps”. Accordingto EPR-spectroscopy results HAs contain stable semi-quinone type radicals in the matrix, which are “traps” for freeshort-living and stable radicals. The novel results of the nitro-blue tetrosol test (NBT-test) have revealed a directantiradical effect of HAs on superoxide anion radical in a wide range of concentrations, which enables to recommend aspecific biological test making use of NBT with non-enzymatic generation of superoxide anion radical for AOAevaluation in HAs. For all HAs samples, high levels of AOA were determined by the voltammetric method as well