Enhancing the Oxidative Stability of Linoleic Acid by Esterification with Hydroxytyrosol

Abstract

This work aimed to evaluate the effect of covalent binding of an antioxidant, hydroxytyrosol, on the oxidative stability of linoleic acid. Hydroxytyrosol was bound to linoleic acid through an ester bond to produce hydroxytyrosol linoleate. The results of 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical-scavenging activity and ferric reducing antioxidant power (FRAP) assays indicated that hydroxytyrosol linoleate retained the main antioxidant activity of hydroxytyrosol. Linoleic acid, hydroxytyrosol linoleate, and linoleic acid with 0.2 mg/g 2,6-di-tert-butyl-4-methylphenol (BHT) were stored under accelerated oxidation conditions (37 °C or illumination) for 9 days. Adding BHT only inhibited the oxidation of linoleic acid for 5 days. In contrast, hydroxytyrosol linoleate inhibited oxidation for 9 days. After 9 days, the peroxide, conjugated diene, thiobarbituric acid reaction substance values, and degradation rate of hydroxytyrosol linoleate were less than 26% of those of linoleic acid. The findings indicate that esterification with hydroxytyrosol can significantly improve the oxidative stability of linoleic acid.