Free radical scavenger and antioxidant capacity correlation of α-tocopherol and Trolox measured by three in vitro methodologies

The objective of this study was to correlate the free radical scavenging and antioxidant activity of two known substances (Trolox and alpha-tocopherol), using three in vitro methods (linoleic acid emulsion, brain homogenate and 2,2-diphenyl-1-picryl-hydrazyl [DPPH]). At steady state, alpha-tocopherol showed a greater inhibition of spontaneous oxidation of brain homogenate (59.42% +/- 1.91) than Trolox (38.50% +/- 2.38), while the latter showed a better antioxidant activity performance regarding inhibition of linoleic acid peroxidation (100% versus 84.02% +/- 1.98) and free radical scavenging activity (93.56% +/- 5.71 versus 66.72% +/- 6.28). When the IC50 value was used as a parameter, alpha-tocopherol presented greater antioxidant activity than Trolox evaluated in brain homogenate and DPPH, without a significant difference when using linoleic acid emulsion. Both compounds showed the same antioxidant efficiency measured by DPPH kinetics (0.37 mM). Antioxidant activity significantly changed according to the substrate, the parameter adopted to compare the substances in the same method and the form used to express antioxidant concentration.