ANTIOXIDATIVE ACTIVITY OF (E)-2-OCTENAL AMINO-ACIDS REACTION-PRODUCTS

The effects of several compounds, previously identified in nonenzymatic browning reactions between oxidized lipids and amino acids, on protecting bulk vegetable oils against oxidation were evaluated to investigate if these naturally formed products may contribute to the overall antioxidative activity of foods. Two amino acid residue analogs, N-(carbobenzyloxy)-L-histidine (Z-His) and N-2-(carbobenzyloxy)-L-lysine (Z-Lys), and their products of reaction with (E)-2-octenal, the Michael adduct 1 and two pyridinium salts, 2 and 3, were added at three levels of concentration (50, 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 (TBARS) assay. Compounds 1-3 significantly decreased TBARS formation on soybean oil (p < 0.05) and showed diverse activity as compared with synthetic antioxidants. The order of effectiveness obtained was 1 much less than 2 approximate to butylated hydroxytoluene approximate to 3 < propyl gallate. These results suggest that some reactions between oxidized lipids and amino acids may contribute to the antioxidant activity of foods in addition to the development of color and fluorescence.