Inhibitory Effects Of Polyphenols From Black Chokeberry On Formation Of Advanced Glycation End-products

Advanced glycation end-products(AGEs)are formed as a result of nonenzymatic glycosylation which is a reaction between the carbonyl of reducing sugars and the free amino residues of proteins.However,elevated concentration of AGEs in vivo is closely related to many chronic diseases such as diabetes,angiocardiopathy and Alzheimer's disease.Many studies have shown that active substance such as flavonoids and polyphenols could inhibit AGEs formation.Black chokeberry,Aronia mlanocarpa(Michx.)Eliott,is abundant with nutrition,especially with polyphenols.This is also an important reason for its antioxidant,anticancer,bacteriostasis and other functions.This thesis,based on the black chokeberry as the raw material,the optimal extraction and purification conditions were studied by the methods of ultrasound assisted and AB-8 macroporous resin.And then polyphenols from black chokeberry was treated as the inhibitor to evaluate the inhibitory effects on reaction products during different reaction steps.The mechanism of inhibition was also studied.The main results were as follows:1.The optimal conditions for ultrasound assisted extraction were as follows:solid-liquid ratio was 1:40 g/mL,ultrasound time was 94 minutes,ultrasound temperature was 50 C.Under this condition,the yield of polyphenols of black chokeberry was 22.09 mg/g.2.The crude polyphenols was isolated and purified by using AB-8 macroporous resin.The static-dynamic adsorption and desorption conditions were studied to determine the best purification conditions:concentration of sample polyphenols was 4 mg/mL,pH was 2.0.The flow rate was 1 mL/min,the volumu of water was 8 BV,ethanol concentration was 70%and the elution rate was 2 mL/min.Under this condition,the purity of purified polyphenols was 64.54%,which was about 4.2 times higher than that before purification,15.37%.HPLC-MS was applied to analyze and preliminarily identify the components of polyphenols,11 monomers were identified.3.Polyphenols of black chokeberry had a good inhibitory effect on glycosylation reaction.Chlorogenic acid(CA)had the highest inhibition rate on fructosamine at the concentration of 200?g/mL within 7 d of incubation,it was 72.27%.At 14 d of incubation,gallocatechin gallate(EGCG)showed the strongest inhibitory effects on a-dicarbonyl compounds and AGEs generation both in the BSA/Glucose and BSA/Glucose/Cu2+systems,the inhibition rate were 84.47%and 70.14%in terms of a-dicarbonyl compounds,for AGEs,the inhibition rate were 48.54%and 54.44%respectively.Meanwhile,EGCG had a good inhibitory effect on BSA secondary structur e modification,and it could increase the amount of a-helix to 21.43%.Overall,EGCG is the primary reason in polyphenols of black chokeberry that had inhibitory effects on glycosylation reaction.And the inhibition mechanism is the result of scavenging free radicals,capturing mental ions and preventing secondary structure changes of proteins.