Binding properties and structure–affinity relationships of food antioxidant butylated hydroxyanisole and its metabolites with lysozyme

Considering the harmful impact of food antioxidants on human bodies, thoroughly exposing their potential effects at the molecular level is important. In this study, the binding interactions of butylated hydroxyanisole (BHA), a phenolic antioxidant, and its different major metabolites tert -butylhydroquinone (TBHQ) and tert -butylbenzoquinone (TBQ) with lysozyme were examined via fluorescence, three-dimensional fluorescence, circular dichroism (CD), and ligand–protein docking studies. The three compounds caused strong quenching of lysozyme fluorescence by a static quenching mechanism but with different quenching efficiencies and different effects on the α-helix content of the lysozyme. The order of binding affinity of lysozyme for all test compounds is as follows: BHA   >   TBQ   >   TBHQ. Thermodynamic parameters indicated that hydrogen bonding and van der Waals forces perform dominant functions in the binding between these compounds and lysozyme. Furthermore, structure–affinity relationships between the model compounds and lysozyme were established on the basis of computational analyses.