Research On The Mechanism Of The Formation Of PhIP And The Inhibition Of PhIP By Flavonoids

Heterocyclic amines(HAAs)are an important class of mutagenic and carcinogenic substances produced in the hot processing of food.In this study,we research the thermal degradation mechanism of creatinine which is an essential precursor of 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine(PhIP)formation.On this basis,we also study the mechanism of the formation of PhIP and the inhibition of PhIP by flavonoids.These results can provide a theoretical basis and new direction for exploring the control and reduction of heterocyclic amine during food thermal processing.Formamide,N-methylformamide,5-Methylhydantoin and 1-methyl-1,3-diazinane-2,4-dione have been identified as the thermal degradation products of creatinine,and N-methylformamide can further produce·NHCHO.According to these results,we suggest the mechanism of creatinine thermal degradation and find that formamide could be the nitrogen source for the formation of PhIP.Then,the effects of formamide and N-methylformamide on the yield of PhIP and the aldol condensation product are studied in the model system of creatinine and phenylacetaldehyde.The experimental results show that the amount of PhIP increased and the amount of the aldol condensation product decreased following the addition of formamide and N-methylformamide.Therefore,formamide/-NHCHO,as the thermal degradation products of creatinine,could react with the aldol condensation product to form PhIP by cyclization reaction.Based on this,a potential concrete pathway for PhIP formation is suggested.And this pathway of PhIP formed from formamide and the aldol condensation product is computed in theory by Gaussian program.The intermediate of this pathway can also be identified by IT-TOF-MS.Both of these results verify the mechanism that formamide can participate in the formation of PhIP with the aldol condensation product.Quercetin and catechin are selected as the representatives of flavonoids,and the specific process of their scavenging free radicals involved in the generation of PhIP is calculated by quantum chemistry.And calculation results show that the inhibitory ability of flavonoids on the formation of PhIP may be related not only to the free radical scavenging ability,but also to the position of scavenged free radicals in the chain reaction to generate PhIP.The earlier the chain reaction that generates PhIP is interrupted,the less the amount of PhIP produced as a product will be.Therefore,the further the free radicals are removed from the final product PhIP in the chain reaction for forming PhIP,the stronger the ability of the flavonoids to inhibit the formation of PhIP.