Interaction Mechanism between α-Lactalbumin and Caffeic Acid: A Multispectroscopic and Molecular Docking Study

Caffeic acid (CA) is a phenolic acid found in a varietyof foods.In this study, the interaction mechanism between alpha-lactalbumin(ALA) and CA was explored with the use of spectroscopic and computationaltechniques. The Stern-Volmer quenching constant data suggesta static mode of quenching between CA and ALA, depicting a gradualdecrease in quenching constants with temperature rise. The bindingconstant, Gibbs free energy, enthalpy, and entropy values at 288,298, and 310 K were calculated, and the obtained values suggest thatthe reaction is spontaneous and exothermic. Both in vitro and in silicostudies show that hydrogen bonding is the dominant force in the CA-ALAinteraction. Ser112 and Lys108 of ALA are predicted to form threehydrogen bonds with CA. The UV-visible spectroscopy measurementsdemonstrated that the absorbance peak A(280nm) increasedafter addition of CA due to conformational change. The secondary structureof ALA was also slightly modified due to CA interaction. The circulardichroism (CD) studies showed that ALA gains more alpha-helicalstructure in response to increasing concentration of CA. The surfacehydrophobicity of ALA is not changed in the presence of ethanol andCA. The present findings shown herein are helpful in understandingthe binding mechanism of CA with whey proteins for the dairy processingindustry and food nutrition security.