| Methylglyoxal(MGO)is an active carbonyl compound that can be produced in vivo and in food processing and increases with increasing reactive oxygen species.In the Maillard reaction pathway,MGO acts as an intermediate active product and then continues to react with protein amino acid residues to produce AGEs.Accumulation of AGEs in vivo can easily lead to oxidative stress in humans and may induce diabetes,nephropathy,atherosclerosis,immunity Defects,aging,inflammation and Alzheimer's disease and other diseases.In this paper,the food additive propyl gallate(PG)was selected to examine the inhibitory effect of PG on MGO,and the inhibitory mechanism of PG inhibiting MGO was analyzed by LC-MS/MS and was furtherverified in the actual oil roasted pork chop,beef cake and other systems.The main research is as follows:1.The synthetic reaction between PG and MGO was constructed,and the product of MM-PG was obtained.MM-PG was isolated and purified by ODS column chromatography and TLC.The purity was more than 98%.The structures were identified by high performance liquid chromatography(HPLC),high resolution mass spectrometry(TOF)and nuclear magnetic resonance(NMR).It was the first time to synthesize MM-PG,a new compound.2.The control PG to examine the biological activity of MM-PG(1)Both PG and MM-PG have good antioxidative ability to scavenge free radicals.Both MM-PG and PG had some reducibility,and increased with the elevated sample concentration,with significant difference(p<0.05).The reducibility of MM-PG is slightly lower than that of PG,except for the concentration of 0.005 mmol/L,at which the reducibility is higher than that of Vc.MM-PG and PG both scavenged DPPH activity at room temperature,and the inhibition rate was positively correlated with the concentration.At 0.5 mmol/L,the DPPH radical scavenging activities of MM-PG and PG were both greater than 90%.Besides,the oxidative stability of Rancimat oil was also studiedandthe results showed that MM-PG could still inhibit the oxidation under high temperature,the induction time was 4.5 times lower than that of PG and higher than that of BHA..(2)Both PG and MM-PG have the ability of eliminating carbonyl free radicals.Both MM-PG and PG could dwindle the content of MGO.When the concentration of MMO was 0.5 mmol/L,MM-PG and PG could both clean over 74%MGO.When MGO/GO co-existed,the clearance rate of MGO/GO by MM-PG could reach more than 55%when MM-PG was 0.5 mmol/L.The inhibition rates of MGO and GO by MM-PG were 27.95%and 70.19%respectively at 120 min after heating.In Lys-glucose system,the inhibitory rates of MM-PG to MGO/GO and AGEs were 45.9%,43.53%and 51.96%respectively when the dosage was 100 p.mol/L.In the soybean 7s protein-glucose system,the inhibitory rates of MM-PG on MGO/GO and AGEs were 62.08%,57.96%and 59.50%respectively when the concentration of the sample reached 1.0 mmol/L.MM-PG still retains the ability of inhibiting MGO/GO and AGEs when the amount of MM-PG added is 0.2 g/kg.The inhibition efficiency can reach 47.9%,38.6%and 50.1%in the roast pork system.The above experimental results show that:After PG captures the adduct formed by MGO,PG still maintain the antioxidation and inhibits the functions of MGO/GO and AGEs.(3)Using LC-MS/MS technology to track and monitor the changes of PG and MM-PG in different systems to speculate the course of action,the results show that:(1)MM-Continue to react with MGO to form a double adduct DM-PG.In(MM-PG)-GO system,MM-PG can still react with GO to form MMMG-PG,a product of PG-MGO-GO.(2)MM-PG,DM-PG,MG-PG,DG-PG and MMMG-PG were formed in PG-MGO-GO system in which PG and MGO/GO coexisted.Here we demonstrate for the first time that PG can capture one molecule of MGO or GO to form MM-PG,MG-PG,capture two molecules of MGO or GO to form DM-PG,and PG-PG can also capture both MGO and GO to form PG PG-MGO-GO adduct.(3)The product of PG was analyzed by LC-MS/MS.The MGO addition product of MM-PG and f DM-PG produced in the system was detected while none GO adducts was found.However,when PG products were analyzed by LC-MS/MS,it was found that PG could conjugated with MGO and GO separately to form MG-PG and MG-PG,or both to form MMMG-PGThe above results clarify the reaction pathway and mechanism of MGO/GO in PG inhibition system,laying a solid theoretical foundation for the application of PG in food. |
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