Interaction of artemisinin and its derivatives with human serum albumin studied using spectroscopies and molecular modeling methods.

The interactions of artemisinins including artemisinin, dihydroartemisinin, artemether and artesunate with human serum albumin (HSA) were studied by fluorescence spectroscopy, UV-Vis absorption spectroscopy, synchronous fluorescence, three-dimensional fluorescence, circular dichroism (CD) and molecular modeling. Results obtained from analysis of fluorescence spectrum and fluorescence intensity indicated that the artemisinins had a strong ability to quench the intrinsic fluorescence of HSA through a static quenching procedure. Furthermore, the association constants K a and the corresponding thermodynamic parameters ΔH, ΔG and ΔS at various temperatures were also calculated. Based on the mechanism of Förster's non-radiative energy transfer theory, the distance between the acceptors and HSA were found. In addition, alteration of the secondary structure of HSA in the presence of the artemisinins was tested by CD spectroscopy. Molecular modeling revealed that the artemisinins were bounded in the large hydrophobic cavity of the site I of HSA.