Inhibitory effects of methylglyoxal (MGO) on the formation of 2-amino-1-methyl-6-phenylimidazo [4,5-b] pyridine (PhIP) in model system

Methylglyoxal was produced by the degradation of glucose, and its role in producing 2-amino-1-methyl-6-phenylimidazo [4,5-b] pyridine (PhIP) was studied attempting to clarify the reaction pathways. The study showed that the PhIP yield was decreased when glucose was added to a mixture of phenylacetaldehyde and creatinine or when methylglyoxal was incorporated into a blend of phenylalanine (phenylacetaldehyde), creatinine and glucose in proportions of 1:1:0.5. PhIP yield was firstly increased and then decreased when glucose was incorporated into a blend of phenylalanine and creatinine. When methylglyoxal was added to the creatinine/phenylacetaldehyde/glucose mixture, methylglyoxal achieved around 83.2% inhibition of PhIP. However methylglyoxal achieved around 39% inhibition of PhIP in the creatinine/phenylalanine/glucose mixture. All of these results indicate that the addition of methylglyoxal to the phenylacetaldehyde/creatinine mixture inhibited the formation of PhIP. A pathway which the inhibitory effect of methylglyoxal on PhIP composition is proposed. Meanwhile, this study explained the ways in which glucose are involved in the composition of PhIP, and helped us better study the formation mechanism of PhIP.