Binding of Catalpol to Bovine Serum albumin in vitro Examined by Spectroscopy and Molecular Modeling

This paper explores the interaction mechanisms between catalpol and bovine serum albumin (BSA) in vitro using the methods of fluorescence quenching, UV-vis absorption, synchronous fluorescence spectroscopy, and molecular modeling. The fluorescence quenching mechanism of BSA by catalpol was confirmed to be a dynamic process. In addition, the UV-vis absorption spectra of BSA in the absence and presence of catalpol provided further evidence for the quenching. Synchronous fluorescence spectra showed that the addition of catalpol did not obviously affect the microenvironment in BSA. This could be explained by the distance between catalpol and Trp residues in protein, which was deduced from the subsequent molecular docking. The theoretical results were further verified by molecular docking analysis. It showed that not only the hydrophobic force but also hydrogen bonds played a role in the interaction of catalpol with BSA.