title: Inhibition of oxidation of methyl linoleate in solution by vitamin E and vitamin C.
abstract: The oxidation of methyl linoleate in solution initiated with azo compounds has been studied in the absence and presence of vitamin E and vitamin C. Both vitamin E and vitamin C acted as a chain-breaking antioxidant and they suppressed the oxidation and produced an induction period. The inhibition rate constant for the scavenging of peroxy radical was calculated at 37 degrees C as kinh = 5.1 X 10(5) M-1 s-1 and 7.5 X 10(4) M-1 s-1 for vitamin E and vitamin C, respectively. It was suggested that each vitamin E could trap two peroxy radicals, whereas vitamin C could trap only one peroxy radical under the reaction conditions employed in this study. When both vitamin E and vitamin C were present, the oxidation was suppressed quite efficiently and the apparent inhibition rate constant was obtained as kinh = 4.0 X 10(5) M-1 s-1. Furthermore, vitamin E remained almost unchanged and only vitamin C was consumed at the initial stage and vitamin E was consumed after vitamin C was exhausted. It was concluded that vitamin E trapped the peroxy radical and the resulting alpha-chromanoxy radical reacted with vitamin C to regenerate vitamin E.
mesh_terms: D001205:Ascorbic Acid; D055598:Chemical Phenomena; D002621:Chemistry; D005609:Free Radicals; D007700:Kinetics; D008041:Linoleic Acids; D010084:Oxidation-Reduction; D012996:Solutions; D014810:Vitamin E
chemical_list: D005609:Free Radicals; D008041:Linoleic Acids; D012996:Solutions; D014810:Vitamin E; C005575:methyl linoleate; D001205:Ascorbic Acid