Studies on the binding of isoalantolactone to human serum albumin by molecular spectroscopy and modeling

1547-1554The interactions between isoalantolactone (IAL) and human serum albumin (HSA) under simulative physiological conditions have been investigated by fluorescence, absorption and circular dichroism spectra. Fluorescence data reveal that the fluorescence quenching of HSA by IAL is the result of formation of the IAL–HSA complex. The thermodynamic parameters, enthalpy change and entropy change for the reaction are calculated to be -34.317 kJ mol–1 and -7.522 J mol–1 K–1, respectively, indicating that the hydrogen bonds and hydrophobic interactions play a dominant role in the binding of IAL to HSA. The conformational investigation shows that the presence of IAL decreases the -helical content of HSA and induces the remarkable unfolding of the polypeptides of protein. Furthermore, displacement experiments using warfarin and ibuprofen indicate that IAL could bind to site I of HSA, which is in agreement with the results obtained from molecular modeling