Antioxidative activity of pyrrole, imidazole, dihydropyridine, and pyridinium salt derivatives produced in oxidized lipid amino acid browning reactions

The antioxidative activity of several models of nonenzymatic browning reaction products was evaluated to determine if the Lipid peroxidation process in the presence of amino acids is always accompanied by formation of products with antioxidative properties. 1-Methylpyrrole (1), 1,2,5-trimethylpyrrole (2), 2-(1-hydroxyethyl)-1-methylpyrrole (3), 2-acetyl-1-methylpyrrole (4), 1-methyl-4-pentyl-1,4-dihydropyridine-3,5-dicarbaldehyde (5), 1-(2-hydroxyethyl)-2-hexyl-3,5-dipentylpyridinium chloride (6), 1-(1-ethyl-2-formylethyl)-4-methylimidazole (7), and 1-(1-ethyl-3-hydroxypropyl)-4-methylimidazole (8) were added at two levels of concentration (100 and 200 ppm) to soybean oil which was oxidized under air in the dark at 60 degrees C. Oil peroxidation was evaluated by using the thiobarbituric acid-reactive substances assay. Compounds 2-8 significantly decreased TEARS formation on soybean oil (p < 0.05) and showed diverse activity as compared among them and with synthetic antioxidants. The order of effectiveness obtained at 200 ppm was 1 < 2 < 3 < 4 approximate to 6 < 7 approximate to 5 < 8 < butylated hydroxytoluene < propyl gallate. These results suggest that reactions between oxidized Lipids and amino acids produce many compounds with antioxidative properties that may contribute to the stability of foods.