An exploration of the interaction, structural characterization and anti-oxidative properties of proanthocyanidin and beta-lactoglobulin complex

Proanthocyanidin (PC) is with antioxidant, anticancer and neuroprotective effects. Cow’s milk beta-lactoglobulin (β-Lg) is reported with higher immunoregulatory activity but lower antioxidative function. In this study, a β-Lg-PC complex was prepared, and the interaction and structural characterization of β-Lg-PC complex were investigated by fluorescence spectral analysis, infrared spectroscopy and molecular docking, etc. PC quenched the intrinsic fluorescence and changed the conformation of β-Lg. The optimal ratio of β-Lg and PC (10:3, w/w) was determined by measuring the particle size and ζ potential. Molecular docking results implied that the covalent binding among complex was mainly concentrated on the binding of PC to amino acid residue ILE 71. Moreover, the antioxidant effects and mechanism of β-Lg-PC complex were explored using LPS-induced oxidative stress model of RAW264.7 cells. The results showed that β-Lg-PC could alleviate oxidative stress by slowing down the LPS-induced decline in SOD enzyme activity, increase in ROS level, loss of mitochondrial membrane potential and increase in apoptosis in RAW264.7 cells.