Stability And Antioxidant Activity Of Bovine Serum Albumin And Blueberry Anthocyanin Complex

The water-soluble pigment anthocyanin riched in blueberry as the research object was selected in this experiment,and the anthocyanin content was determined under different factors by pH differential method,the kinetic equation was simulated,and the anthocyanin degradation rate and half-life was analyzed.UV-Vis,Fluorescence,Circular Dichroism,and molecular docking were used to explore the interaction and the mechanism between BSA and Malvidin-3-galactoside?MG?.ABTS,TAOC and pH differential method were used to investigate the antioxidant capacity and stability of blueberry anthocyanin before and after adding BSA under different conditions,which provided a theoretical basis for the application of blueberry anthocyanin in processing and production.The main findings are as follows:1.Degradation kinetics and stability of anthocyanins in blueberryThe thermal degradation of anthocyanins conformed to the first-order kinetics equation under different pH values.Under strong acid conditions,the thermal stability of anthocyanins was stronger than that of weak acids and neutrals.The thermal stability of anthocyanins was poor.As the temperature increased,the anthocyanin degradation rate k increased,the half-life t1/2 and D values decreased significantly,and the activation energy Ea was the lowest at pH6.0,which was 44.77 kJ/mol.The maximum activation energy Ea was 83.73 kJ/mol at pH 1.0.The thermal degradation reaction is an endothermic non-spontaneous reaction.Light and H2O2 could increase the degradation of anthocyanins,and the anthocyanins degradation complied with first order kinetics,the rate of degradation and the half-life in the light conditions was 0.0148 d-1 and 47 d,respectively.The rate increased significantly with increasing H2O2 concentration.In addition,0.2%Na₂SO₃ inhibited the degradation of anthocyanins,while 0.05%,0.1%,and 0.15%Na₂SO₃ promoted the anthocyanin degradation reaction.2.Mechanism of the interaction between MG and BSAThe interaction of MG with BSA was studied,and the fluorescence spectra showed that MG and BSA emitted a static quenching,and the binding site was approximately one.The thermodynamic analysis showed that the interaction between MG and BSA was a spontaneous process with the electrostatic interaction as the main force.The transfer between molecules can occur with the distance of 3.5 nm.Synchronous fluorescence spectra showed that the hydrophobicity of the microenvironment of Try residues and Tyr residues decreased,and the polarity increased.CD spectra showed that the secondary structure of BSA would be changed by MG,in which?-helix content was increased,?-sheet,turn angle,and irregular curling content was decreased.The results of molecular docking showed that MG was mainly bound in the II and III domains of BSA by hydrogen bonds and electrostatic interaction.The hydroxy group on the B ring of MG was bound to BSA,resulting in the non-expressed antioxidant activity of MG.3.Effect of BSA on the stability and antioxidant activity of anthocyanins in bluberryThe effect of different concentrations of BSA on blueberry anthocyanins content under light,Vc+light and sucrose+light conditions was studied by pH differential method.The effect of 0.15 mg/mL BSA on the antioxidant capacity of anthocyanins was measured by ABTS and TAOC methods under the three treatment conditions.The conclusions were as follows:under all three conditions,blueberry anthocyanins was degraded to varying degrees.The degradation of anthocyanins under sucrose and Vc treatments was higher than that under only light treatment.The stability of anthocyanins under the three treatment conditions was protected after adding BSA.When the concentration of BSA was 0.15 mg/mL,the protective effect was best.The result of antioxidant activity tests showed that the antioxidant capacity of anthocyanins was inhibited after binding to BSA.However,when there were unfavorable factors of anthocyanins stability,BSA could retain the antioxidant capacity of anthocyanins by protecting the stability of anthocyanins.