Antioxidant activity and kinetics studies of quercetin, epicatechin and naringenin in bulk methyl linoleate

Abstract

The objective of this work was to evaluate the antioxidant action of flavonoids with specific differences in chemical structure, namely, quercetin (Q), epicatechin (E) and naringenin (N), in bulk methyl linoleate (ML) under different oxidation conditions at 60 °C, in an oven and in a Rancimat apparatus. The oxidation kinetics were studied by direct and concomitant analysis of primary and secondary oxidation compounds. Addition of 200 mg/kg of E or Q to ML increased about tenfold the oxidative stability of ML. The protective effect was significantly higher for E, independent of the oxidation conditions used. However, N showed no effect. Results obtained were attributed to differences in structural features and polarity. Thus, the presence of the ortho-dihydroxy structure in the B ring and the 3-hydroxyl group in the C ring of E and Q seemed to be determinant and the comparatively higher polarity of E may have enhanced its antioxidant efficiency.