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Optimization of extraction conditions for determination of Oxygen Radical Scavenging Activity in amaranth

Amaranth is one of the few plants that produce significant amount of edible 'cereal-like' grain crop. In addition to its high protein and iron content, recent studies on amaranth antioxidant potential have not yielded consistent results. The objective of this study was to analyze factors that can contribute to the extraction of antioxidants in order to provide recommendations for optimal extraction conditions for achieving accurate amaranth Oxygen Radical Absorbance Capacity (ORAC- FL). In addition, total phenolic content was also investigated in all conducted experiments. We used ORAC- FL assay with respect to its area-under- the- curve technique for antiradical evaluation and Golden software <<Grapher>> for its illustration and quantification. Among all investigated reaction mixtures acidified 30 % methanol extract (pH 1.4) reached the highest ORAC- FL activity (275.39 μmol TE/g DM). On <<Grapher>> plot images, observed shape and decay of the amaranth’s curve showed similarity to the published ORAC-FL curves of pure phenolics. Therefore, using the Folin-Ciocalteu analysis, phenolics were evaluated and correlated with ORAC- FL activity. Significant correlation was found, suggesting that total phenolic content increases amaranth’s antioxidant activity (r = 0.5338, p = 0.0404) but that major role in antioxidant defense still remains to the other non- phenolic compounds. In conclusion, due to the variety of radical scavenging activity assays and inconsistent data on literature amaranth antioxidant potential, our study for the first time provided recommendations for the higher efficiency of antioxidant extraction in order to inspire more detailed amaranth antioxidant research.

Amaranth; solvent extraction; ORAC- FL assay; Antioxidant activity

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