Binding of isofraxidin to bovine serum albumin

The binding of isofraxidin to bovine serum albumin (BSA) was studied under physiological conditions with BSA concentration of 1.5×10^-6 mol · L^-1 and drug concentration in the range of 1.67×10^-6 mol · L^-1 to 2.0×10^-5 mol · L^-1. Fluorescence quenching spectra in combination with uv absorption spectroscopy, Fourier transform infrared (FTIR) spectroscopy, and CD spectroscopy was used to determine the drug-binding mode, binding constant, and the protein structure changes in the presence of isofraxidin in aqueous solution. The linearity of Scatchard plot indicates that isofraxidin binds to a single class of binding sites on BSA and the values given for the binding constants agree very closely with those obtained by the modified Stern-Volmer equation. The thermodynamic parameters, enthalpy change ((delta)H) and entropy change ((delta)S), were calculated to be -17.63 kJ · mol^-1 and 51.38 J · mol^-1 · K^-1 according to the vanʹt Hoff equation, which indicated that hydrophobic interaction played a main role in the binding of isofraxidin to BSA.