Total antioxidant capacity assessment by a development of an antioxidant assay based on green synthesized MnO2nanosheets

Abstract The determination of total antioxidant capacity (TAC) as an integration activity of several antioxidants in samples is a significant parameter in the analysis of biological or food matrices. In this study, MnO2 nanosheets were for the first time employed for TAC measurements. Gum Arabic, a highly branched polysaccharide, was both the reducing and templating agent for the synthesis of MnO2 nanosheets. MnO2 nanosheets are a potent oxidizing agent to oxidize tetramethylbenzidine (TMB) in physiological pH to a blue product. Due to the redox reaction between MnO2 nanosheets and antioxidants, the color intensity of the MnO2 mixture in the presence of antioxidants decreased and the absorbance difference of the resulting suspension was measured at 652 nm. The trolox equivalent antioxidant capacity (TEAC) values of several antioxidant compounds were also measured using the new assay and conventional standard CUPRAC assay (r = 0.989). Under an optimal condition, linear concentration range, detection limit, precision and accuracy of the proposed assay were evaluated for the detection of various antioxidant compounds and represented the reliability and robustness of this assay. This assay was operated in physiological pH and could be applicable in the detection of TAC in the biological samples.