Multi-spectroscopies and molecular docking insights into the interaction mechanism and antioxidant activity of astaxanthin and β-lactoglobulin nanodispersions

In this study, interaction mechanism of astaxanthin (AST) with beta-lactoglobulin (beta-La) nanodispersions that were prepared by emulsification-evaporation method was investigated using multi-spectroscopies and molecular docking. Further, the antioxidant activity of the resultant nanodispersions was evaluated. The AST was successfully bound to the beta-La and spontaneous interaction between beta-La and AST complex was established. Hydrophobic interactions between beta-La and AST were the dominant force that maintained the binding affinity. The nanodispersions were characterized by a static quenching of intrinsic fluorescence of the beta-La, an increased particle size of beta-La and AST complex and a decreased surface hydrophobicity of beta-La. Molecular docking investigation of the nanodispersions elucidated that a linear molecule of AST was partly inserted into the hydrophobic core of beta-La, which located at the internal cavity of beta-barrel of beta-La and encompassed by hydrophobic amino acid residues. The binding between beta-La and AST significantly (P < 0.05) enhanced 2,2'-azino-bis-3-ethylbenzthiazoline-6-sulphonic acid (ABTS) radical scavenging activity and intracellular reactive oxygen species scavenging ability of AST. The ABTS scavenging ability of AST in beta-La/AST nanodispersion was almost fourfold higher than that of the individual AST. This study provided evidence that suggests the incorporation of AST in dairy products could have great potential to enhance the functionality of the dairy products and convey better activity than the individual components.

Automated summary

This study investigated the interaction mechanism between astaxanthin and beta-lactoglobulin nanodispersions, finding that hydrophobic interactions played a dominant role. The resultant nanodispersions showed changes in the properties of beta-lactoglobulin and enhanced antioxidant activity of astaxanthin. The molecular docking investigation revealed the potential for improved functionality in dairy products by incorporating astaxanthin.