Evaluation of solvent effects on the DPPH reactivity for determining the antioxidant activity in oil matrix

Reactivity of 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical in methanol, ethanol, isopropanol, isooctane, and ethyl acetate, was evaluated to assess the antioxidant capabilities in medium chain triacylglycerol. DPPH loss values were obtained over 30 min, with sampling every 5 min. Even the same concentration of antioxidants showed different DPPH reactivity depending on solvent. In methanol, 5 min was enough for alpha-tocopherol to react with DPPH, whereas BHT did not react with DPPH even after 30 min. Gallate series showed higher DPPH reactivity than TBHQ, sesamol, or BHA in methanol, while lower reactivity in isooctane. Antioxidants in ethanol and isopropanol reacted with DPPH less efficiently compared to those in methanol, the exception being sesamol. DPPH reactivity of gallate series in isooctane was lower than that of sesamol, TBHQ, and alpha-tocopherol. Combinatorial usage of methanol and isooctane for DPPH reactivity could provide reliable information on the antioxidant capacities of chemicals in edible oils.

Automated summary

This study evaluated the reactivity of 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical in five different solvents to assess the antioxidant capabilities in medium chain triacylglycerol. The results showed that antioxidants exhibited varying reactivity with DPPH depending on the solvent used, with a combination of methanol and isooctane providing reliable information on antioxidant capacities in edible oils.