Molecular characterization of capsaicin binding interactions with ovalbumin and casein

Abstract

Capsaicin (CAP) rich diets may help with a variety of human pathophysiological conditions; however, CAP administration is difficult due to its high pungency and limited water solubility. This study comprehensively explored the mechanism of CAP binding with ovalbumin (OVA) and casein (CAS) by multi-spectroscopic, thermodynamics, and molecular docking simulation at pH 7.4, as well as the prospect of employing these food proteins as CAP carriers. The findings demonstrated that CAP could interact with OVA/CAS and increase their fluorescence intensity, which was followed by specific protein conformational changes. According to the ITC data, the interaction between CAP and OVA/CAS proceeded spontaneously, with hydrogen bonding and hydrophobic interactions governing the binding process. The binding constant Ka for the CAP-OVA and CAP-CAS complexes was determined by ITC to be 1.07 ± 0.21 ⅹ 105 M−1 and 2.22 ± 0.14 ⅹ 105 M−1, respectively. Molecular docking analysis further indicated the existence of a high affinity CAP binding site on OVA and CAS, supporting the experimental findings. Moreover, the data demonstrated that CAP binding interactions with these proteins led to the formation of complexes with about 97% CAP encapsulation efficiency, contributing to a synergistic enhancement in their antioxidant activity. Therefore, this study implies that OVA and CAS have great potential for being utilized as edible delivery vehicles for lipophilic bioactive molecules such as CAP.