Correlation Between Acrylamide And Melanoidins And Primary Investigation On Toxicity Metabolism In Vitro

Acrylamide(AA) results from the Maillard reaction between asparagine(Asn)/reducing sugars in heat-processed food,which is known to be a neurotoxic,genotoxic compound and probable carcinogen. Formation of melanoidins has also been found in the complex Maillard reaction,which exhibited remarkable antioxidant,antimutagenic and scavenging active oxigen properties.It was well known that AA catalyzed by P450 2E1 in vivo was converted into glycidamide(GA),which attacked as electrophile guanine in DNA to produce N-7-(2-carbamoyl-2-hydroxy-ethyl) guanine.Exogenous antioxidant can inhibit acrylamide toxicity by controlling epoxidation process of converting into glycidamide and holding back aggression of glycidamide such as Vitamine C,Methionine,Allicin,etc.Melanoidins which exhibited significant antioxidant capacity,antimutagenic capacity and scavenging active oxygen properties are closed to food antioxidants such as Butylated hydroxyanisole,Dibutylhydroxytoluene,Vitamine C,etc.It is worth to be explored urgently on the relationship between the formation of melanoidins and AA,which aims to further investigation on melanoidins inhibiting toxic metabolism of AA.This study was to attempt to model the formation of acrylamide in a glucose/asparagines(Glu/Asn) reaction system at various conditions,in order to investigate the relations between the formation of acrylamide and melanoidins.Furthermore,primary investigation was taken to model melanoidins inhibiting toxic metabolism of AA.To sum up,the thesis obtained the main conclusions as follows.First,acrylamide as product was determined by reversed-phase high performance liquid chromatography-diode array detection (RP-HPLC-DAD) in Glu/Asn model system.The concentration of AA in model reaction was investigated at various conditions.The formation of AA intensity increased with an increase of temperature(120～180℃) and heating time(0～6min).A steady increase of acrylamide level was observed at 120℃.The higher level of acrylamide was obtained at 140℃for 20min(1.46μg/mL),150℃for 10min(2.55μg/mL),160℃for 6min(3.05μg/mL),180℃for 2min(2.01μg/mL),and then reduced. Except for lactose,The Maillard reaction the other sugars and Asn prouduced AA.In fructose model,more AA was formed(relative yield of fructose/the other sugars,2～4).Fructose and sucrose accelerate the formation of AA in Glu/Asn model system,whereas xylose and maltose inhibit he formation of AA in Glu/Asn model system.The effect of sugars on the concentration of acrylamide in Glu/Asn reaction is positive and significant.The formation of AA increased with an increase of concentration of Glu at 0.0～0.3mol/L.There exists obvious correlation between AA and pH(R~2=0.9670) at pH6～8.AA increases with pH.2.The relations between the formation of acrylamide and melanoidins under various conditions were investigated in model Maillard reaction.Equimolar solution(0.2mol/L) of Glu and Asn were heated at different temperatures(120～180℃).A steady increase of melanoidins level was observed at 120℃for 60min.At higher temperatures(140,150,160,180℃),the higher level of melanoidins was obtained at 20min(175mmol/L),15min(131mmol/L),6min(137mmol/L), 2min(120 mmol/L).The formation of melanoidins increased steadily with an increase of concentration of Glu at 0～0.2mol/L.The concentration of AA increased with concentration of melanoidins at 0～140mmol/L,and then reduced above140mmol/L.A clear correlation between formation melanoidins and AA were observed in model Maillard reaction.3.Melanoidins is obviously correlative with AA,which exhibited remarkable antioxidant,antimutagenic and scavenging active oxygen properties.Therefore,it was concluded that melanoidins as endogenous antioxidantcan inhibit acrylamide toxicity metabolism by controlling epoxidation process and glycidamide aggression to guanine in DNA.The vitro metabolism model was investigated primarily.P450 2E1 in SD rats hepatic microsomal froaction was induced by 5%acetone.The microsomal froaction was prepared with Calcium sediment and was separated with cryogenic highspeed centrifugation.Concentration of protein in rat hepatic microsomal froaction determinated by the dying method with coomassie brilliant blue was 19.45mg/mL.AA chromatograph peak wasn't found after increasing AA and P450 2E1 concentration,prolonging incubation time and so on.It was conclude that the other AA metabolism enzyme in organism and cell microenvironment were lost in rat hepatic microsomal froaction.AA couldn't were epoxidized by single P450 2E1.