Formation of a creatinine thermal degradation product and its role and participation in the radical pathway of forming the pyridine ring of 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP).

Creatinine, commonly found in muscle tissue, has been demonstrated as an essential precursor of 2-amino-1-methyl-6-phenylimidazo [4, 5-b] pyridine (PhIP) in thermally possessed foods. In this current study, formamide and N-methylformamide were identified as the main thermal degradation products of creatinine. The raised production of PhIP and the decreased level of aldol condensation product occurred simultaneously with the increased addition of formamide in the model system of creatinine and phenylacetaldehyde. It was demonstrated that formamide reacted with the aldol condensation product to close the pyridine ring to form PhIP. The radical pathway of PhIP formation was then proposed and verified by density functional theory (DFT) computation and an ion-trap time-of-flight mass spectrometer (IT-TOF-MS). This is the first report of the role of the creatinine thermal degradation product in the pathway of PhIP formation, which could facilitate potential strategies against the inhibition of PhIP formation in thermally processed foods.
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