Probing the interaction of tert-butylhydroquinone and its β-cyclodextrin inclusion complex with bovine serum albumin

Tert-butylhydroquinone (TBHQ) is a synthetic antioxidant found widely in foods such as cooking oil, fried baked goods and meat products, however, if consumed in excessive quantities, it may cause nutritional problems and chronic diseases. The binding of TBHQ to transport protein before and after β-cyclodextrin (β-CD) encapsulation was investigated by multiple spectroscopies and molecular docking technology. At 298 K, the binding constant, enthalpy, and entropy of bovine serum albumin (BSA) with TBHQ were (1.18±1.50) × 104 M-1, (-110.11±15.29) kJ mol-1 and (-293.36±50.87) J mol-1 K-1 at 298 K, respectively. By forming a stable complex with BSA through van der Waals forces and hydrogen bonds, TBHQ altered BSA's secondary structure and microenvironmental polarity. However, the binding affinity of TBHQ with BSA decreased after encapsulation by β-CD, but the binding distance increased. Because of the encapsulation of β-CD, the interference of TBHQ with the BSA conformation was also inhibited. Fourier transform infrared spectroscopy, X-ray diffraction, and scanning electron microscope study confirmed the formation of an inclusion complex between CD and TBHQ. According to UV spectroscopy, TBHQ and β-CD have a binding constant of (1.21±0.03) ×103 M-1. The formation of TBHQ–β-CD inclusion complex inhibited the binding of TBHQ and BSA, possibly because the inclusion of β-CD prevented TBHQ from entering the hydrophobic cavity of BSA, which prevented TBHQ from binding to BSA, alleviating the negative effects of TBHQ on BSA conformation. The 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging results showed that the antioxidant activity of TBHQ was not affected by β-CD encapsulation.