Preparation And Stability Of Bighead Carp(Aristichthys Nobilis) Antioxidant Peptide And Its Nanoparticles

Fish-derived bioactive peptides have gained significant interest owing to their diverse range of activities.However,these peptides are susceptible to enzymatic degradation in the gastrointestinal tract and undergo reactions such as oxidation and hydrolysis when exposed to processing environments.To address these challenges,this study examined the impact of various environments on the bioactivity of bighead carp peptide and subsequently developed chitosan nanoparticles to enhance its stability during gastrointestinal transit and enable controlled release.These findings could have significant implications for the wider application of bioactive peptides in the food and pharmaceutical industries.The effects of different pH values,temperature,metal ions,food raw materials and simulated gastrointestinal digestion on antioxidant activity（ABTS free radical scavenging capacity,DPPH free radical scavenging capacity,reducing capacity）were investigated.Results revealed that the DPPH radical scavenging ability and reducing ability were inhibited by alkaline and high-temperature environments,while the ABTS radical scavenging ability remained high in an alkaline environment.Glucose was found to enhance antioxidant activity,while sucrose was beneficial to the enhancement of reducing power and DPPH radical scavenging ability,but not to ABTS radical scavenging ability.Na Cl was found to be beneficial to free radical scavenging of polypeptides but had an inhibitory effect on reducing power.Compared with K⁺and Cu²⁺,Mg²⁺has a significant inhibitory effect on reducing capacity.After simulated digestion,reducing power and ABTS radical scavenging capacity increased by 12.5%and 25%,respectively,while DPPH radical scavenging capacity decreased by 92%.Moreover,the secondary structure and microstructure also changed with the increase of fluorescence intensity.Using the encapsulation rate as the primary index and the polydispersity index（PDI）and Zeta potential as reference indices,the optimum preparation conditions for bighead carp peptide chitosan nanoparticles were selected through a single-factor test.The study also analyzed the retention rate of polypeptides before and after encapsulation in simulated.The results showed that the optimal preparation conditions for the nanoparticles were a chitosan molecular weight of 50 k Da,a chitosan solution pH value of 4,a chitosan solution mass concentration of 0.5 mg/m L,and a chitosan to sodium tripolyphosphate mass ratio of 6:1.Under these optimal conditions,the encapsulation rate was 79.6%,the particle size was 212 nm,the PDI was 0.411,and the Zeta potential was+30.8 m V.The FTIR spectra demonstrated that chitosan was crosslinked with sodium tripolyphosphate and that bighead carp peptide was enclosed within the chitosan nanoparticles.The study also found that the thermal stability of bighead carp peptide chitosan nanoparticles improved compared to unencapsulated peptides,and that the retention rate of peptides during simulated digestion increased.The optimized conditions,including a molecular weight of 5 k Da,a mass ratio of chitosan to flaxseed gum of 1:2,and a pH of 3.5,were found to produce nanoparticles with a diameter of 155.1 nm.The encapsulation efficiency of bighead carp peptide was found to be 60.3%.The nanoparticles were nearly uniformly spherical in shape,and FTIR spectra confirmed the existence of hydrogen bonding and electrostatic interactions among the components of the nanoparticles.Compared with bighead carp peptide,the thermal stability of the loaded nanoparticles was improved.In vitro release of the nanoparticles followed the first-order kinetic model,indicating that the release process is controllable.The present study investigated the effects of pH value,ionic strength,simulated digestion,and storage on two types of chitosan nanoparticles.Furthermore,Caco-2 cells were utilized as models to investigate the cytocompatibility,antioxidant capacity,and internalization capacity of the nanoparticles.The results showed that both types of nanoparticles exhibited high stability under acidic conditions.Moreover,Na⁺and Cl^-were found to weaken the electrostatic repulsion between droplets,leading to particle aggregation.Encapsulated of bighead carp peptide with chitosan nanoparticles improved the stability of the peptide.Cell experiments demonstrated that the both types of nanoparticles exhibited high biocompatibility and antioxidant ability in vivo.Furthermore,the nanoparticles improved the permeability of bighead crap peptide in vivo.