Formation And Reduction Mechanism Of Heterocyclic Aromatic Amine (PhIp) In Model System Reaction

Heterocyclic aromatic amines(HAAs), produced in meats cooked at the high temperature, is a risk factor for certain human cancers. In view of their potent mutagenic activity and the fact that they can be formed even during ordinary household cooking. More than 25 HAAs have been isolated and identified from food and model systems. Among all of them, the thermic 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine(PhIP) is one of the most abundant HAA produced in foods. The International Agency for Research on Cancer(2004) collated the studies on PhIP as probably carcinogenic to humans. Therefore, PhIP has attracted wide attention in the field of food. In this paper, this study explained the ways in which glucose are involved or not involved in the formation of PhIP in model system. This study is suggested to be the role of methylglyoxal on the formation of PhIP in model system. Moreover, a systemic research was carried out to indicate the effect of the metal cations, sugarcane molasses, SCA and waxy rice starch on the formation of PhIP in model system. The main results and conclusions are as follows:In this experiment, phenylacetaldehyde is detected using derivatization, and tested by a high performance liquid chromatography with a diode array detector(HPLC-DAD), synthesis and characterization of 2-PB that are produced by phenylacetaldehyde derivatization. A new method for the detection of phenyl acetaldehyde is developed, this method demonstrated high resolution and satisfied sensitive with respect to the prior routine methods in simultaneous analysis of phenylacetaldehyde. A detect method for the study of the change of phenylacetaldehyde in model system is provided.A pathway of methylglyoxal inhibited the formation of PhIP is proposed. This pathway is suggested to be the role of methylglyoxal on the formation of PhIP. An intermediate product of model reaction will react with methylglyoxal to produce the compound(9), thus would suppress the formation of PhIP. In addition, in the creatinine/phenylalanine reaction system, when the glucose content reached half the concentration of creatinine, the formation of PhIP was maximum. This result may be explained by the balance between the promoting strecker degradation and inhibition of PhIP formation by methylglyoxal.This study aimed to investigate in detail the changes to PhIP and its precursors in the presence of some cations(i.e., K+, Na+, Ca2+, Mg2+, Fe2+ and Fe3+) in a creatinine/phenylacetaldehyde model system. The study showed that PhIP yields not changed when K+ and Na+ were added to a mixture of phenylacetaldehyde and creatinine. Because K+ and Na+ cannot disturb the reaction of phenylacetaldehyde and creatinine, not influence aldol condensation product formation. The study found that PhIP yields decreased when Fe2+and Fe3+ were added to a mixture of phenylacetaldehyde and creatinine. This decrease may be attributed to the fact that Fe3+ can form complexes with various properties with creatinine and accelerate creatinine degradation. This pathway can disturb the reaction with phenylacetaldehyde, influence aldol condensation product formation, and suppress PhIP formation. Furthermore, Ca2+and Mg2+ enhanced PhIP contents. Such enhancement may be attributed to the fact that CaCl2 and MgCl2 promote aldol and aldol condensation product reactions with ammonia and formaldehyde. A possible mechanism of the cations during PhIP formation in the model system is also proposed.In this study, sugarcane molasses extract was investigated for its total phenolic content and in vitro antioxidant capacity. Chemical model system showed that the sugarcane molasses extract effectively reduced the formation of phenylacetaldehyde and the aldol condensation product, meanwhile the amount of 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine(PhIP) also decreased. Probablely because the reaction between the phenolic compounds of sugarcane molasses extract and the carbonyl group of phenylacetaldehyde inhibited the aldol condensation product formation, and then would suppress the formation of PhIP. A pathway that phenolic compounds inhibited the formation of PhIP is proposed. This pathway also suggested the mechanism that how the sugarcane affect the formation of PhIP. The results of the current study would be useful in producing an effective additive to minimize PhIP formation in cooked meats, the sugarcane molasses extract suggest a great potential for practical application in daily cuisine.In this study, the effects of waxy rice starch and short chain amylose(SCA) from debranched waxy rice starch on the formation of PhIP in model system were investigated and compared. The results showed that addition of waxy rice starch and SCA significantly decreased PhIP, and the effect of SCA was more pronounced than that of waxy rice starch. This decrease may be attributed to the fact that the glucose residues of starch condense with amino group of creatinine formed N-Glycosyl conjugate. But the main components of waxy rice starch and SCA are different. Waxy rice starch is known as composed of highly polymerized amylopectin. In this study SCA is composed of the short chain amylose. Amylose has an essentially unbranched α[1â†'4] linked glucan, and amylose chains can form double helices. The glucosyl hydroxyl groups of α[1â†'4] glucose chains are located on the outer surface of the helix. This characteristic structure of amylose may easily produce to reaction of SCA with creatinine. However, the structure of amylopectin is very complex, and amylopectin has chains of α[1â†'4] linked glucoses arranged in a highly branched structure with α[1â†'6] branching links. Meanwhile, the complex spatial structure of amylopectin disturbs the reaction of glucosyl hydroxyl groups of glucose with amino group of creatinine in model reaction. So the effect of SCA was more pronounced than that of waxy rice starch on suppressing PhIP formation.