Structural Elucidation And Activity Studies Of Fucosylated Chondroitin Sulfate From Intestinal Wall Of Sea Cucumber Stichopus Japonicas

The utilization rate of sea cucumber intestines is low,the study of physiological activity is not valued,and the structure of polysaccharides and other components is not clear.In fact,polysaccharides and other components in sea cucumber intestines have good activities such as antioxidant.The metal in food industry is facing the problem of antisepsis,so safe,non-toxic and side-effect corrosion inhibitor is needed.The purpose of this study is to analyze the structure of sea cucumber intestinal wall polysaccharides to fill the gap in structure,to study the antioxidant activity of sea cucumber intestinal wall polysaccharides to develop natural and non-toxic antioxidants,and to study the corrosion inhibition performance of sea cucumber intestinal wall polysaccharides to develop food corrosion inhibitors.A fucosylated chondroitin sulfate was isolated from the Intestinal wall of sea cucumber Stichopus japonicus(FCSiw)),whose structure was characterized by NMR spectroscopy.Two fucosyl residues were found:2,4-disulfated-fucose(Fuc2,4S),4-sulfated-fucose(Fuc4S),which were only linked to the O-3 of glucuronic acid residues(Glc A).Besides mono-fucosyl moieties,di-fucosyl branches,namely Fuc2,4S?(1?3)Fuc4S,were also found to be attached to the O-3 of Glc A.The DPPH method and the ABTS method were used to detect the antioxidant activity of FCSiw,the results showed that FCSiw had certain scavenging ability to these two free radicals,and the scavenging ability increased with the increase of FCSiw's concentration,but its scavenging abiliity was lower than Vc's scavenge abiliity.FCSiw was evaluated as a potential inhibitor using weight loss test,electrochemical investigations,SEM and AFM methods.Weight loss measurement exhibited the percentage inhibition efficiency of96.03%for FCSiw and in the optimum concentration of 625 mg/L at 35?.Polarization diagrams revealed that the FCSiw behaved as a mixed type inhibitor and mainly inhibited the anodic process.The inhibition performance of FCSiw was optimized by factorial experimental designs,the optimized conditions for the minimum corrosion rate were C FCSiw=625 mg/L,t=7 h,T=35?.Surface morphology by SEM and AFM confirmed the effectiveness of the inhibitor.Density functional theory(DFT)disclosed that the electron donor(E_HOMO)and electron acceptor(E_LUMO)of FCSiw forms strong chemical bonds with the vacant d-orbital of mild steel surface.These results indicate that FCS_iw can be used as corrosion inhibitor for low carbon steel and other materials,and it has potential application value in the field of metal corrosion prevention of stored food due to its advantages of non-toxicity,high efficiency,environmental friendliness and edible.In conclusion,FCS_iw has a similar structure to the polysaccharide in the body wall of sea cucumber Stichopus japonicus,and has certain antioxidant at the same time.FCSiw itself as a mixed corrosion inhibitor has a good corrosion inhibition performance,which can be used in food field of metal corrosion.