Molecular mechanism of the protective effect of monomer polyvinylpyrrolidone on antioxidants - experimental and...

We previously developed a lutein-polyvinylpyrrolidone (PVP) complex with improved aqueous saturation solubility and stability, though the conjugation mechanism is still unclear. In this paper, experiments with astaxanthin-PVP complex and curcumin-PVP complex were carried out, which indicated that PVP could improve the solubility and stability of astaxanthin and curcumin. We aimed to construct a computational model capable of understanding the protective effect in complexes formed between PVP and antioxidants, through which the binding mode of PVP and antioxidants was investigated with molecular modelling in order to obtain the interactions, binding energy, binding site and surface area between PVP and antioxidants. Solubility enhancement was attributed to the H-bonds between PVP and antioxidants, and the saturation solubility was curcumin > lutein > astaxanthin. Binding energy, binding site and surface area were beneficial for the stability of complex, and the stability enhancement was lutein > astaxanthin > curcumin. The experimental results were in agreement with the computational results. Furthermore, we established a method for the exploration of a similar system with other polymer complexes. Additionally, the proposed PVP model could predict the interactions between PVP and various ligands, such as antioxidants and drugs.