Investigation of binding interaction between bovine α-lactalbumin and procyanidin B2 by spectroscopic methods and molecular docking

• Procyanidin B2 complexation changed the spatial structure of α-lactalbumin. • The interaction was a spontaneous and exothermic process driven by hydrogen bonds. • Docking study showed α-lactalbumin had five binding sites for procyanidin B2. • α-Lactalbumin showed the great potential for binding and stabilizing procyanidin B2. The interactions between bovine α-lactalbumin and procyanidin B2 were fully investigated by spectroscopic methods and molecular docking. This study hypothesized that ALA could spontaneously interact with procyanidin B2 to form protein-based complex delivery carrier. Far UV CD and FTIR data demonstrated ALA’s secondary structures were altered and intrinsic fluorescence quenching suggested ALA conformation was changed with procyanidin B2. Calorimetric technique illustrated ALA-procyanidin B2 complexation was a spontaneous and exothermic process with the number of binding site (n, 3.53) and the binding constant (K b , 2.16 × 10 4 M −1 ). A stable nano-delivery system with ALA can be formed for encapsulating, stabilizing and delivering procyanidin B2. Molecular docking study further elucidated that hydrogen bonds dominated procyanidin B2 binding to ALA in a hydrophobic pocket. This study shows great potential in using ALA as protein-based nanocarriers for oral delivery of hydrophilic nutraceuticals, because procyanidin B2-loaded ALA complex delivery systems can be spontaneously formed.