Study on simultaneous binding of resveratrol and curcumin to β-lactoglobulin: Multi-spectroscopic, molecular docking and molecular dynamics simulation approaches

Worldwide popularization of natural polyphenol urges preparation of multi-ligand protecting and transporting system. Simultaneous binding of resveratrol (RES) and curcumin (CUR) with bovine β-lactoglobulin (β-LG) was investigated using multi-spectroscopic, molecular docking and molecular dynamics simulation approaches. Fluorescence quenching experiment indicated that both ligands existed simultaneously and quenched fluorescence intensity of β-LG in static mode. The sequence in which the ligands were added affected binding affinity of each polyphenol. Binding of RES and CUR to β-LG gave uniform ternary complexes with high stability at size scale below 100 nm and zeta potential at around −20 mV. Interacting with RES and CUR did not change secondary structure content of β-LG significantly (p > 0.05). Fourier-Transform Infrared Spectroscopy (FT-IR), X-ray diffraction (XRD) and Differential scanning calorimeter (DSC) results confirmed that RES and CUR were successfully encapsulated in β-LG concurrently. Combination of β-LG with RES and CUR improved the ABTS savaging ability of small molecules significantly (p < 0.05) and remained relatively constant during irradiation for 160 min. Molecular docking indicated that RES and CUR attached differently on β-LG depending on addition sequence. Molecular dynamics simulation revealed that both RES and CUR showed smallest space between start structure and equilibrium structure in ternary system with addition sequence of CUR and then RES. Data may provide useful information for application of β-LG as effective co-delivery of bioactive polyphenol compounds with different hydrophobicity and molecular weight.