Effect of lipid oxidation products on the formation of 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) in model systems

Ternary mixtures of creatinine, phenylalanine and lipids (or carbohydrates) were heated at 200 degrees C for 1 h to determine the potential contribution of lipids to the formation of 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP). Although unoxidised lipids did not contribute to PhIP formation, their oxidation produced many compounds that significantly increased the formation of PhIP. Among the different lipid oxidation products (LOPS) studied, which included omega-6 and omega-3 derived lipid hydroperoxides, 2,4-alkadienals, 2-alkenals, 4,5-epoxy-2-alkenals, 4-oxo-2-alkenals, and 4-hydroxy-2-nonenal, 4-oxo-2-nonenal was the most reactive compound. It produced 32.48 pmol of PhIP/mu mol of creatinine in comparison with the 7.92 pmol of PhIPh/mu mol of creatinine produced by the control phenylalanine/creatinine reaction mixture. 4-Oxo-2-nonenal reactivity was similar to that of most carbohydrates; although ribose and arabinose produced more PhIP (44-46 pmol of PhIP/mu mol of creatinine). In addition to single LOP, the addition of oxidised soybean oil for 24-144 h at 60 degrees C also increased PhIP formation. All these results pointed out to a potential contribution of LOP to the formation of PhIP in food products. This contribution will depend on the lipid content of the food product and its easiness to be oxidised. (C) 2012 Elsevier Ltd. All rights reserved.