Effects of phenolic propyl esters on the oxidative stability of refined sunflower oil

The oxidative stability of refined sunflower oil in the presence and in the absence of propyl caffeate (PC), propyl hydrocaffeate (PHC), propyl ferula te (PF), and propyl isoferulate (PI) has been evaluated according to the Ra ncimat method. The antioxidant activity of the phenolic derivatives was com pared with that obtained with native [alpha -tocopherol (alpha -TOH)] and s ynthetic [propyl gallate (PG)] antioxidants. The results allow the establis hment of a decreasing order of antioxidant power: PG > PHC > PC much greate r than alpha -TOH > PI > PF. The oxidative stability was improved neither b y the addition of PF nor by a supplement of alpha -TOH. Moreover, a positiv e antioxidant effect was obtained for PC that was placed between those of a lpha -TOH and PG. The antioxidant activity of PHC was higher than that of i ts analogue (PC). A dose-dependent effect was observed for PG, PHC, and PC. A chain-breaking mechanism was proposed for the antioxidant activity of pr opyl phenolic esters because the same ranking order of efficacy was obtaine d for their antiradical activities evaluated by using the 2,2-diphenyl-1-pi crylhydrazyl radical method.