Antioxidant activity and mechanism of action of ferulic and caffeic acids in different lipid systems

摘要

The antioxidative properties of ferulic and caffeic acids were studied in the concentration range 0.02 - 0.20 % (1.03 x 10~(-3) -11.12 x 10~(-3) M) during autoxidation of triacylglycerols of olive oil (TGOO),triacylglycerols of sunflower oil (TGSO),and triacylglycerols of soybean oil (TGSBO) at 100 deg C.The stabilization factor (F) as a measure of the effectiveness,the oxidation rate ratio (ORR) as a measure of the strength,and the activity (A) which combines the above two factors were determined.The effectiveness of ferulic and caffeic acids increased in the following sequence for the investigated lipid substrates: TGSO < TGSBO < TGOO.Caffeic acid was a much more effective antioxidant in comparison with ferulic acid.The complex kinetic parameter A for the two phenolic acids was one order of magnitude higher in TGOO than in TGSO and TGSBO.In the three lipid systems,the activity of caffeic acid was two orders of magnitude higher than the activity of ferulic acid.Kinetic interpretation of the results enabled clarifying the mechanism of the antioxidative action of the inhibitors.The molecules of ferulic and caffeic acid participated in one side reaction of inhibited oxidation,i.e.reaction with the hydroperoxides: InH + LOOH -> products.The rate constant of this reaction was much lower in TGOO than in TGSO and TGSBO.The radicals of ferulic acid in TGOO and in TGSBO,and the radicals of caffeic acid in TGOO,TGSO and TGSBO participated in one side reaction of chain propagation,i.e.reaction with the lipid substrate: In~* + LH ->InH + L~*.Ferulic acid participated in the initiation reactions with a much higher rate than caffeic acid did .Besides,the rate of participation of phenolic acids in initiation reactions increased with increasing the oxidizability of the lipid systems: TGOO < TGSO < TGSBO.Keywords,antioxidants,ferulic acid,caffeic acid,triacylglycerols,olive oil,sunflower oil,soybean oil