Studies on the interaction between homological proteins and anthocyanins from purple sweet potato (PSP): Structural characterization, binding mechanism and stability

The protein-bound anthocyanin complexes are naturally existed in food systems by their spontaneous interaction. In this study, the interaction mechanism of homological proteins (p-PSP) and anthocyanins (FAC-PSP) was investigated to explore the binding characteristic of native protein-bound anthocyanins from purple sweet potato (p-BAC-PSP). The structural characterization, stability and anti-ultraviolet property of p-BAC-PSP were also evaluated. Results revealed that hydrophobic interaction is dominant binding force for forming p-BAC-PSP. The binding resulted in protein secondary structure changes with more β-sheet and lower β-turn, random coil structures. Fluorescence spectroscopy demonstrated that FAC-PSP quenched p-PSP fluorescence in a combination of static and dynamic mode (static dominant) with a binding constant of 105 L/mol reflecting strong affinity of FAC-PSP to p-PSP. Moreover, the complex form exhibited better protective effects on anthocyanins for pH, light, thermal stabilities and higher anti-ultraviolet activity. These findings further expanded the application of anthocyanins as stable, functional food and cosmetic ingredients.