Temperature-Dependent Mechanism of Antioxidant Activity of o-Hydroxyl, o-Methoxy, and Alkyl Ester Derivatives of p-Hydroxybenzoic Acid in Fish Oil

The autoxidation of purified fish oil in the presence of different concentrations of o-hydroxyl, o-methoxy, and alkyl ester derivatives of p-hydroxybenzoic at 35-55 A degrees C was evaluated by different kinetic parameters including the stabilizing factor as a measure of effectiveness, the oxidation rate ratio as a measure of strength, and the antioxidant activity which combines the two parameters. Methyl gallate as the most reactive antioxidant participated only in the main reaction of chain termination (ROO center dot A + InH ROOH + In center dot). Gallic acid, ethyl protocatechuate, protocatechuic acid, vanillic acid, and syringic acid, were able to protect fish oil against oxidation in terms of the extent of their participation in the pro-oxidative side reactions of chain initiation (InH + ROOH In center dot A + RO center dot A + H2O and InH + O-2 In center dot A + HOO center dot) and the antioxidative side reactions of chain propagation (In center dot A + ROO center dot In-OOR and In center dot A + In center dot products).