Antioxidative Activity of Non-Enzymatically Browned Proteins by Reaction with Lipid Oxidation Products

Summary Three oxidized lipid/amino acid reaction (OLAARP): (1-methyl-4-pentyl-1,4-dihydropyridine-3,5-dicarbaldehyde, 1-(5′-amino-1′-carboxypentyl)pyrrole, and N -(carbobenzyloxy)-1(3)-(1′-(formyl(methyl)-hexyl)-L-histidine dehydrate), and two browned proteins (the monomer and the dimmer produced in the reaction between BSA and 4,5( E )-epoxy-2- E )-hepatenal) were prepared and tested for antioxidative activity in a microsomal system in order to investigate the antioxidative function of OLAARP and non-enzymatically browned proteins in biological systems. The microsomal sytem consisted fo freshly prepared trout muscle microsomes, which were oxidized with Cu 2+ , Fe 3+ /ascorbate, or Cu 2+ /H 2 O 2 at 37 °C and in the presence of the compound to be tested as antioxidant. The three OLAARP (tested at 50 μM) and the two browned proteins (tested at 40 μg/mL) efficiently protected against lipid peroxidation, assessed by the formation of thiobarbituric acid-reactive substances, and protein damage, determined by amino acid analysis. These results suggest that the formation of non-enzymatically browned proteins by reaction with lipid oxidation products may constitute an antioxidative defense mechanism, which could play a significant role in vivo .