Evaluation of the antioxidant activity of vegetable oils based on luminol chemiluminescence in a microemulsion

Abstract

AbstractA flow injection analysis (FIA) methodology has been developed for the estimation of the radical scavenging activity (RSA) of edible oils as a measure of their antioxidant activity. The RSA determination was based on the inhibition of the luminol chemiluminescence (CL) induced by the Fenton's reagent in a microemuslion (n‐hexane in water). At the optimum operational conditions, the RSA of gallic acid and buthylhydroxylanisol, usually employed as antioxidant in vegetable oils, as well as corn, sunflower, olive, soybean and sesame oils, were measured in terms of the IC50 (the concentration required to reduce in 50% the CL emission measured in the absence of antioxidants in the organic phase). For this purpose, the percentage of the CL inhibition (%Inh) against the sample concentration was plotting. Virgin oils of sesame and olive showed the greatest RSA, which was associated to their elevated concentration of natural antioxidants, such as phenols, tocopherols and lignans. The refined soybean oil also has an important antioxidant activity due to the addition of synthetic antioxidants after the refining process, while the lower RSA activities were found in the refined corn and sunflower oils. The results of the proposed method showed good agreement with those obtained by the DPPH test, which suggests that it could be used as a complementary method for the evaluation of hydrophobic substances with antioxidant properties.