ADDITION OF OXIDIZED LIPID/AMINO ACID REACTION-PRODUCTS DELAYS THE PEROXIDATION INITIATED IN A SOYBEAN OIL

The antioxidative activity of 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, N-(carbobenzyloxy)-1(3)[1'-(formylmethyl)hexyl]-L-histidine dihydrate (1), 1-[N-2-(carbobenzyloxy)L-lysyl]-2-[3'-carboxy-2'-(E)-propen-1'-yl]-4-pentylpyridinium betaine (2), and bis[1-(N-2-carbobenzyloxy)-L-lysyl]-2-(3'-carboxy-2'-propene- 1',2'-diyl)-4-pentylpyridinium betaine (isomeric mixture) (3), mere studied to evaluate if some oxidized lipid/amino acid reaction products might play a role in delaying an initiated peroxidative process in a vegetable oil. All of these compounds were added at two levels of concentration (100 and 200 ppm) to partly oxidized soybean oil which was further oxidized under air in the dark at 60 degrees C. Oil peroxidation was evaluated by using the thiobarbituric acid-reactive substances (TEARS) assay. Compounds 1-3 significantly delayed new TEARS formation on soybean oil (p < 0.05) and showed diverse activity as compared with synthetic antioxidants. The order of effectiveness obtained was Z-His < Z-Lys < 1 < 2 approximate to BHT approximate to 3 < propyl gallate. These results suggest that some oxidized lipid/amino acid reaction products might be,playing an antioxidative role in foods by delaying the peroxidative process at the same time that they are being produced.