Analysis of binding properties and interaction of thiabendazole and its metabolite with human serum albumin via multiple spectroscopic methods.

Thiabendazole (TBZ), which is oxidized into 5-hydroxythiabendazole (5-OH-TBZ) in vivo, is a commonly used food preservative. Interactions of TBZ and 5-OH-TBZ with human serum albumin (HSA) were comprehensively studied via multiple spectroscopic methods and molecular docking. This study focussed on the mechanistic and structural information on binding of TBZ and 5-OH-TBZ to HSA to evaluate the impact of the food additive on HSA. H NMR spectra of the two ligands showed the binding exists. ITC and fluorescence spectroscopy results revealed that TBZ was a stronger ligand, with a binding constant of 10l/mol and formed a more stable complex with HSA than did 5-OH-TBZ via electrostatic interaction. Spectroscopic results (UV-vis, FT-IR, and CD) showed that TBZ and 5-OH-TBZ caused conformational changes in HSA, in which α-helix and β-turn transformed into β-sheet, causing HSA structure to loosen. Docking programs showed that both TBZ and 5-OH-TBZ bound to HSA via IB.