Simultaneous Scavenging Mechanism Of Amino Acids For Reactive Carbonyl Species And Cytotoxicity Of Their Products

Methylglyoxal(MGO),formaldehyde(FA)and acrolein(Acr)are reactive carbonyl species(RCS)which can produce simultaneously during processing,storage in foods,as well as biochemical metabolism in living organisms.The previous studies have shown that many diseases are closely related to RCS,making RCS scavengers as a hot topic in food safety and medicine.In addition to be important nutrients,amino acids exhibit various functions in humans.Our research team found that amino acids can efficiently scavenge single RCS,such as Acr,5-hydroxymethylfurfural and acrylamide,however,amino acids have not been used to simultaneously eliminate multiple RCS.Since various RCS co-exist in foods,in this research,the scavenging capacity and reaction mechanism of amino acids for FA along with MGO or FA along with Acr were investigated.The main results are as follows:1.Scavenging mechanism of amino acids for MGO along with FA as well as the cytotoxicity of their productsThe scavenging capacity of 14 amino acids for MGO and FA were investigated.Three amino acids,γ-aminobutyric acid,serine and glycine,which expressed high scavenging capacity and produced stable scavenging products were selected to investigate the elimination mechanism and the cytotoxicity of the scavenging products.It was found that the addition of FA promoted the elimination of MGO by amino acids at three temperatures(37 ℃,80 ℃ and160 ℃);increase of temperature elevated the elimination of MGO and FA.On this basis,the reaction products of three amino acids with MGO along with FA were prepared and purified.The products were identified as imidazole salts with a nitrogen-containing five-membered ring and a maximum absorption peak at 220 nm.The reaction mechanism was nucleophilic addition reaction of two molecules of amino acids with one molecule of FA and one molecule of MGO.Imidazole salts can be detected in baked and fried food.Their formation markedly decreased the cytotoxicity of their precursors,MGO and FA.2.Scavenging capacity and mechanism of amino acids for FA along with AcrAmino acids not only have efficient elimination rate of Acr at various temperatures(37 ℃,80 ℃ and 160 ℃),among which the elimination rate of GABA is as high as 99%,but also a part of FA can be eliminated in the form of Acr-FA-AA products with a maximum absorption peak at 267 nm.The reaction mechanism is as follows: After one molecule of amino acid reacted with two molecules of Acr via the Michael addition reaction,the intermediate reacted with one molecule of FA via an aldol condensation reaction to form a pyridine ring compound with the basic structure of 5-formyl-3-methyl-1,2,3,6-tetrahydropyridine.The pyridine products can be detected in baked and fried food.3.Cytotoxicity and detoxification mechanism of Acr-FA-AA adductsThe cytotoxicity of Caco-2 and GES-1 cells incubated with six Acr-FA-AA adducts was lower than that of Acr or Acr along with FA(Acr-FA).Then,Acr-FA-GABA and Acr-FA-Thr were selected to investigate the detoxifying mechanisms,including ROS level,apoptosis,cell cycle and DNA damage.It was found that cells with the treatments of Acr and Acr-FA showed significantly abnormal ROS levels,cell cycle arrest,and DNA damage,resulting in massive cell apoptosis,while the reaction products can detoxify its precursor substances through prevention of ROS production,cell cycle arrest,and DNA damage.As a result,the apoptosis greatly decreased and and the cell viability increased.