Study on the interaction of tussilagone with human serum albumin (HSA) by spectroscopic and molecular docking techniques

Abstract

Tussilagone is a sesquiterpenoid which exhibits a variety of pharmacological activities. The interaction of tussilagone with human serum albumin (HSA) was investigated using fluorescence spectroscopy, UV–vis absorption, fluorescence probe experiments, synchronous fluorescence, circular dichroism (CD) spectra, three-dimensional spectra and molecular docking techniques under simulative physiological conditions. The results clarified that the fluorescence quenching of HSA by tussilagone was a static quenching process as a result of HSA-tussilagone (1:1) complex. Tussilagone spontaneously bound to HSA in site I (subdomain IIA), which was primarily driven by hydrophobic forces and hydrogen bonds (ΔH° = −13.89 kJ mol−1, ΔS° = 16.39 J mol−1 K−1). The binding constant was calculated to be 2.182 × 103 L mol−1 and the binding distance was estimated to be 2.07 nm at 291 K, showing the occurrence of fluorescence energy transfer. The results of CD, synchronous and three-dimensional fluorescence spectra all revealed that tussilagone induced the conformational changes of HSA. Meanwhile, the study of molecular docking also indicated that tussilagone could bind to the site I of HSA mainly by hydrophobic and hydrogen bond interactions.