Multispectroscopic and molecular modeling studies on the interaction of bile acids with bovine serum albumin (BSA)

Bile acids (BAs) as the main components in two Traditional Chinese Medicine (TCM) of Calculus bovis (niu huang) and Bear bile (xiong dan) have been used for curing hepatic and biliary disorders for decades. However, their severe side effects as injections dramatically hampered their medical development. In this study, the interaction of BAs with bovine serum albumin (BSA) was investigated through multi spectroscopic and molecular docking techniques to primarily reveal the physiological effects of BAs at the molecular level. The Stern-Volmer analysis of fluorescence quenching data showed the presence of static quenching mechanism. Thermodynamic parameters of this interaction revealed that the predominant intermolecular force between BAs and BSA was the hydrogen binding or Vander walls interactions. The number of binding sites was calculated by Langmuir adsorption model of single molecule. The combination of BAs-BSA was moderate intensity because the binding constant KLB was lower than the combination of other drugs with BSA. This indicated the safety of BAs. Furthermore, the results from synchronous fluorescence technique and Fourier transform infrared spectroscopy represented that BAs had little effects on the structure of BSA. The diverse binding sites for various BAs with the protein BSA were substantiated by molecular docking studies. These results can contribute to the development and renovation of BAs drugs through revealing the interaction between BAs and BSA. (C) 2018 Elsevier B.V. All rights reserved.