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-(carbo benzyloxy)-L-histidine (Z-His) and N-2-(carbobenzyloxy)-L-lysine (Z-Ly s), and their products of reaction with (E)-2-octenal, enzyloxy)-1(3)[ 1'-(formylmethyl)hexyl]-L-histidine dihydrate (1), 3'-carboxy-2'-(E)-p ropen-1'-yl]-4-pentylpyridinium betaine (2), and carbobenzyloxy)-L-lys yl]-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 initiat ed peroxidative process in a vegetable oil. All of these compounds wer e added at two levels of concentration (100 and 200 ppm) to partly oxi dized soybean oil which was further oxidized under air in the dark at 60 degrees C. Oil peroxidation was evaluated by using the thiobarbitur ic acid-reactive substances (TEARS) assay. Compounds 1-3 significantly delayed new TEARS formation on soybean oil (p < 0.05) and showed dive rse activity as compared with synthetic antioxidants. The order of eff ectiveness obtained was Z-His < Z-Lys < 1 < 2 approximate to BHT appro ximate 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 th at they are being produced.