Study of the interaction between icariin and human serum albumin by fluorescence spectroscopy

The interaction between icariin and human serum albumin (HSA) in physiological buffer (pH 7.4) was investigated by fluorescence and UV–Vis absorption spectroscopy. Results obtained from analysis of fluorescence spectrum and fluorescence intensity indicated that icariin has a strong ability to quench the intrinsic fluorescence of HSA through a static quenching procedure. The thermodynamic parameters, ΔHθ and ΔSθ, were calculated to be 12.29 kJ mol−1 > 0, and 47.08 J mol−1 K−1 > 0, respectively, which suggested that hydrophobic force plays a major role in the reaction of icariin with HSA. The binding constants of icariin with HSA were determined at different temperatures by fluorescence quenching method. The distance r between donor (HSA) and acceptor (icariin) was calculated to be 4.18 nm based on Förster’s non-radiative energy transfer theory. The results of synchronous fluorescence spectra and three-dimensional fluorescence spectra showed that binding of icariin to HSA can induce conformational changes in HSA.