Structural And Biological Activity Analyses Of Short Peptide Chelated Complex From Channa Argus

The structure characteristics and biological activity of short peptide chelated complex from Channa Argus were investigated in several aspects to provide a novel method and theoretical analyses for deep processing the Channa argus: 1) optimizating the preparation procedure for chelating short peptide of Channa Argus with different metal ions; 2) the structural analysis of the chelating complexes; 3) establishing the in vitro digestion model and applying it in digestion and absorption ratios determination of the chelating metal ions; 4) evaluating the antioxidant activity of the different chelate metal ions. The main results of this paper are as follows:(1) Signal factor and response surface experiments were combined to optimize the process conditions for chelating the short peptide of Channa Argus with Ga2+, Fe2+, Zn2+, respectively. The optimal conditions for chelating calcium were: enzyme dosage=35000 U/g, p H = 6.0, the weight ratio of peptides/calcium chloride =5:1(W/W), reaction temperature = 40 oC, reaction time = 30 min. The chelating rate of 59.59% was achieved. The optimal conditions for chelating iron were: enzyme dosage =35000 U/g, pH = 6.0, the weight ratio of peptides/ iron chloride =3:1(W/W), reaction temperature = 25 oC, reaction time = 30 min. The chelating rate of 84.46% was achieved. The optimal conditions for chelating zinc were: enzyme dosage =35000 U/g, pH = 7.0, the weight ratio of peptides/ zinc chloride =2:1(W/W), reaction temperature = 70 oC, reaction time = 60 min. The chelating rate of 64.85% was achieved.(2) The chelating products were characterized by ultraviolet/infrared spectroscopy, SEM and other measurements. A obvious shift of the maximum peak was observed in the ultraviolet absorption spectrum of the short peptide after chelation. For chelating calcium and chelating zinc it was red shift, while, for chelating iron, it was purple shift. Besides, the position and the intensity of the short peptide’s characteristic absorption peak were varied in the infrared spectrum after chelation. These verified the chelating metal ions were formed and the reaction was happened between the metal ions and short peptide carboxyl and/or amino. The amino acid composition analysis implied acidic amino acid hydroxy participated in the chelating reaction since the glutamic acid and aspartic acid increased through the chelation process. The SEM images showed there were crystal grains at the surface of the chelating products, implying the adsorption between metal ions and short peptide. The particle size and viscosity measurements indicated the average particle sizes of the short peptides declined, while the viscosity increased.(3) The simulated digestion and absorption, and oxidative stability of the chelating products were studied. Under the simulated stomach environment, the metal ions in the chelating complex were released to free ions. However, under the simulated intestinal tract environment, the increase of pH led to the further chelation between metal ions and short peptide. Then, the hydrolyzation of the short peptide resulted in the release of the metal ions, again. The metal ions could be absorbed in the form of free ions or chelating complex, which improved its digestibility. Moreover, all these three kinds of chelating complex were able to remo ve DPPH, superoxide anion and H2O2, implying their antioxidant activity.