Pyridinones Are Not Antioxidants As Shown by Kinetics of Free Radical Autoxidation, but They Prevent Radical Oxidations Catalyzed by Toxic Heavy Metals

Three 2-methyl-3-hydroxypyridinones, 1-methyl-, 1; 1-(4-methoxy)phenyl-, 2; and 1-(4-dimethylamino)phenyl-, 3, were discovered not to possess strong antioxidant properties contrary to literature reports. These pyridinones were not active chain-breaking antioxidants toward peroxyl radicals generated from styrene or methyl oleate initiated by azobis-2-methylpropylnitrile (AIBN) in solution compared to known phenolic antioxidants, 2,2,5,7,8-pentamethyl-6-hydroxychroman (PMHC) or 2,6-di-tert-butyl-4-methoxyphenyl (DBHA). Pyridinone 2 exhibited weak antioxidant activity in cumene, kinh = 1.3 × 103 M–1 s–1, compared to 2,6-di-tert-butyl-4-methylphenol (BHT), kinh = 4.3 × 103 M–1 s–1. The pyridinones were not active antioxidants during lipid peroxidation initiated by azobis-2-amidinopropane·2HCl (ABAP) in aqueous–lipid dispersions of 0.50 M sodium dodecyl sulfate (SDS) micelles where 2 did not inhibit peroxidation of methyl oleate at pH 7.0 or 4.0, while BHT exhibited effective suppression of oxygen uptake. In a...