Comparison of Various Assays of Antioxidant Activity/Capacity: Limited Significance of Redox Potentials of Oxidants/Indicators

  • Int J Mol Sci. 2025 Jul 23;26(15):7069. doi: 10.3390/ijms26157069.
Paulina Furdak  1  2 ,  Kacper Kut  1 ,  Grzegorz Bartosz  1 ,  Izabela Sadowska-Bartosz  1
Affiliations
  • 1. Laboratory of Analytical Biochemistry, Institute of Food Technology and Nutrition, Faculty of Technology and Life Sciences, University of Rzeszow, 4 Zelwerowicza Street, 35-601 Rzeszów, Poland.
  • 2. Doctoral School, University of Rzeszow, 16C Rejtana Street, 35-959 Rzeszów, Poland.
PMID: 40806202 DOI: 10.3390/ijms26157069
Abstract

Assays of total antioxidant capacity (TAC) of complex Materials bring no information on the composition of Antioxidants present in a sample. As the thermodynamic condition for a redox reaction is that redox potential of the oxidant must be higher than that of a reductant (Antioxidants), it seemed to be of interest whether it is possible to estimate the content of Antioxidants of various ranges of redox potentials using a set of assays employing oxidants/indicators of different values of redox potentials. Antioxidant activities of nine Antioxidants and TAC of an aqueous garlic extract were estimated using nine assays of Eo' of oxidants/indicators ranging from 0.11 to 1.15 V. The antioxidant activities were expressed in mol Trolox equivalents/mol compound. The thermodynamic conditions made some Antioxidants unreactive with indicators of sufficiently low Eo', but otherwise, no dependence between the antioxidant activities and redox potentials of oxidants/indicators and reactivities of Antioxidants was observed. TAC of the garlic extract did not show any regular dependence on the redox potential of the oxidant/indicator, being the highest in the test of 2,2'-azinobis-(3-ethylbenzothiazoline-6-sulfonate) radical (ABTS•) decolorization. These results indicate that kinetic factors play a primary role in determining the antioxidant activities of Antioxidants and TAC in various assays.

Keywords
2,6-dichlorophenolindophenol; ABTS; Cupric Ion Reducing Antioxidant Capacity; Ferric Reducing Antioxidant Power; Oxygen Radical Absorbance Capacity; TAC; Trolox; antioxidants; ferricyanide; o-phenanthroline.
Products