Preparation,Structure Characterization And Antioxidant Activity Of Burdock Polysaccharide-Chlorogenic Acid Complex

Burdock is rich in polysaccharides and chlorogenic acid.Burdock polysaccharide has various physiological activities such as antioxidant,hypoglycemic,immune regulation and intestinal flora regulation.Besides,it is easy to prepare,safe and stable,and can be used as a carrier to deliver active substances.Chlorogenic acid has a variety of biological activities,such as antioxidant,antibacterial and anti-inflammatory,antiviral,regulating blood sugar and blood pressure balance,but its poor stability limits the play of biological activities.In this study,burdock polysaccharide-chlorogenic acid complex was prepared and its structure characterization,physical and chemical properties and antioxidant activity were studied to promote the bioactivity of chlorogenic acid,and to study whether there is synergistic antioxidant effect,so as to provide theoretical basis and technical support for the research and development of new antioxidant products.The main research contents and results are as follows:(1)Construction of burdock polysaccharide-chlorogenic acid complexAfter the burdock root was crushed and sieved,the polysaccharide was extracted by hot water extraction method.After degreasing and protein removal,the burdock polysaccharide was obtained by dialysis and freeze drying.According to the different mass ratios of burdock polysaccharide and chlorogenic acid,sample solutions with different concentrations were prepared,and the complex ratio with the strongest antioxidant effect was selected as burdock polysaccharide:chlorogenic acid=1:3 by constructing metronidazole-induced oxidative damage model of zebrafish,and the antioxidant activity of complex at this ratio was 1.1 to 1.9times that of other ratios.(2)Structure characterization of burdock polysaccharide-chlorogenic acid complexThe structure of the complex was characterized by ultraviolet spectrum,infrared spectrum,particle size,zeta potential,scanning electron microscopy,X-ray diffraction and thermogravimetric analysis.The results showed that most of the size distribution of burdock polysaccharide-chlorogenic acid complex was 50?60 nm,and the zeta potential was-6.36±0.80 m V,showing an amorphous sheet structure with different sizes,rough surface and relatively compact texture.No new double bond was formed during the combination between polysaccharide and chlorogenic acid,which was mainly the result of hydrogen bonding.(3)Physical and chemical properties of burdock polysaccharide-chlorogenic acid complexThe storage stability,thermal stability,light stability and in vitro digestion characteristics of burdock polysaccharide-chlorogenic acid complex were studied.The low-temperature storage effect of burdock polysaccharide-chlorogenic acid complex was better than normal temperature storage,and the content of chlorogenic acid did not change significantly within15 days,indicating that the complex had good storage stability in a short time.After heat treatment at 40,60,80 and 100?,the particle size,polydispersity index(PDI),zeta potential and chlorogenic acid content of the complex only had small changes,which indicated that it had good thermal stability.After light treatment,the particle size,PDI,zeta potential and chlorogenic acid content of the complex changed significantly,indicating that light affected the stability of the complex.The digestibility of the complex was more than 55%after simulated gastric digestion in vitro,and as high as 85%after simulated intestinal digestion in vitro.(4)Antioxidant activity of burdock polysaccharide-chlorogenic acid complexIn vivo antioxidant study results showed that the activities of total superoxide dismutase(T-SOD)and catalase(CAT)in zebrafish treated with the complex increased by 1.45 and 3.92times,and the malondialdehyde(MDA)content decreased by 2.53 times,respectively,compared with the model group,which could effectively inhibit the oxidative damage of the body.In vitro antioxidant study results showed that the complex showed good scavenging ability on DPPH,ABTS⁺,OH^-,and O₂^-free radicals,with IC₅₀ values of 0.095,0.35,1.06 and0.73 mg/m L,respectively,which were close to chlorogenic acid.