Antioxidant activity and mechanism of action of thymol and carvacrol in two lipid systems

The autoxidation of purified triacylglycerols of lard and sunflower oil (TG L and TGSO) containing 0.02, 0.05, 0.10 and 0.20% thymol and carvacrol was studied at ambient temperature. The results obtained with the inhibited lip id systems (thymol - TGL; carvacrol - TGL; thymol - TGSO and carvacrol - TG SO) showed that thymol had the highest antioxidant effectiveness and activi ty during TGSO oxidation. Thymol and carvacrol participated in one side rea ction during inhibited TGL oxidation, and thymol took part in two side reac tions during TGSO oxidation. Carvacrol molecules did not participate in sid e reactions during TGSO oxidation. Thymol and carvacrol contributed to chai n initiation to a higher degree during TGSO oxidation than during TGL oxida tion. Thymol radicals did not participate in chain propagation during TGL a nd TGSO oxidation. Carvacrol radicals took part in one reaction of chain pr opagation in both lipid systems. In general, during autoxidation of lipids at ambient temperature, thymol is a more effective and more active antioxid ant than carvacrol. Both antioxidants differ in the mechanism of their inhi biting action which depends on the character of the lipid medium. Thymol is a better antioxidant in TGSO than in TGL, whereas the activity of carvacro l in the two lipid systems does not differ significantly. (C) 1998 Elsevier Science Ltd. All rights reserved.