ANTIOXIDATIVE ACTIVITY OF PHENOLIC-ACIDS ON TRIACYLGLYCEROLS AND FATTY-ACID METHYL-ESTERS FROM OLIVE OIL

The autoxidation of kinetically pure triacylglycerols and methyl ester s of olive oil (TGOO and MEOO) in the presence of four different conce ntrations of p-coumaric, ferulic and caffeic acids at 100 degrees C wa s studied. It was established that effectiveness and strength of the p henolic acids were greater in MEOO than in TGOO. In both lipid substat es the molecules of phenolic acids participate in one side-reaction (w ith hydroperoxides). The rate constants of this reaction in TGOO and i n MEOO are practically the same. The phenolic acids take part in chain initiation. The rate of this reaction for ferulic and caffeic acids h as equal values in TGOO and in MEOO, whereas for p-coumaric acid it is twice as high in TGOO than in MEOO. The radicals of the phenolic acid s participate in one reaction of chain propagation (with the lipid sub strate) both in triacylglycerols and in methyl esters of olive oil. Co mparison with the data published recently for sunflower oil triacylgly cerols and methyl esters demonstrates the strong influence of the unsa turation type and degree of the lipid system on the kinetics and mecha nism of the antioxidative action of the phenolic acids. Copyright (C) 1996 Elsevier Science Ltd