Multi-spectroscopic studies on the interaction of human serum albumin with astilbin: Binding characteristics and structural analysis

Five spectroscopic techniques were used to investigate the interaction of astilbin (ASN) with human serum albumin (HSA). UV–vis absorption measurements prove that ASN–HSA complex can be formed. The analysis of fluorescence spectra reveal that in the presence of ASN, quenching mechanism of HSA is considered as static quenching. The quenching rate constant kq, KSV and the binding constant K were estimated. According to the vanʹt Hoff equation, the thermodynamic parameters enthalpy change (ΔΗ) and entropy change (ΔS) were calculated to be −12.94 kJ mol−1 and 35.92 J mol−1 K−1, respectively. These indicate that the hydrophobic interaction is the major forces between ASN and HSA, but the hydrogen bond interaction cannot be excluded. The changes in the secondary structure of HSA which was induced by ASN were determined by circular dichroism (CD), Fourier transform infrared spectroscopy (FT-IR) and Raman spectroscopy.