title: Binding of the bioactive compound 5,7,4'-trihydroxy-6,3',5'-trimethoxyflavone to human serum albumin.
abstract: 5,7,4'-trihydroxy-6,3',5'-trimethoxyflavone is one of the bioactive components isolated from Artemisia plants possessing antitumor therapeutic activities. In this paper, its binding properties and binding sites located on human serum albumin (HSA) have been studied using UV absorption spectroscopy, fluorescence spectroscopy and Fourier transform infrared (FT-IR) spectra. The results of fluorescence titration revealed that 5,7,4'-trihydroxy-6,3',5'-trimethoxyflavone could strongly quench the intrinsic fluorescence of HSA by static quenching and there was only one class of binding sites on HSA for this drug. The binding constants at four different temperatures (289, 298, 310, and 318 K) were 1.93, 1.56, 1.22, and 0.93x10(5) L mol-1, respectively. The FT-IR spectra evidence showed that the protein secondary structure changed with reduction of alpha-helices about 27.6% at the drug to protein molar ratio of 3. The thermodynamic functions standard enthalpy change (DeltaH0) and standard entropy change (DeltaS0) for the reaction were calculated to be -18.70 kJ mol-1 and 36.62 J mol-1 K-1 according to the van't Hoff equation. These results and the molecular modeling study suggested that hydrophobic interaction was the predominant intermolecular force stabilizing the complex, and 5,7,4'-trihydroxy-6,3',5'-trimethoxyflavone could bind to the site I of HSA (the Warfarin Binding site).
authors.affiliation: Department of Chemistry, Lanzhou University, Lanzhou 730000, PR China. tangjh03@st.lzu.edu.cn
authors.forename: Jianghong
authors.initials: J
authors.lastname: Tang
authors.forename: Weiping
authors.initials: W
authors.lastname: Wang
authors.forename: Feng
authors.initials: F
authors.lastname: Luan
authors.forename: Xingguo
authors.initials: X
authors.lastname: Chen
mesh_terms: D001665:Binding Sites; D001688:Biological Products / Q000737:chemistry*; D005419:Flavonoids / Q000737:chemistry*; D006801:Humans; D006860:Hydrogen Bonding; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008956:Models, Chemical; D008958:Models, Molecular; D011485:Protein Binding; D017433:Protein Structure, Secondary; D012709:Serum Albumin / Q000737:chemistry*; D013053:Spectrophotometry; D017550:Spectroscopy, Fourier Transform Infrared; D055672:Static Electricity; D013696:Temperature; D013816:Thermodynamics; D014466:Ultraviolet Rays
chemical_list: C432985:5,7,4'-trihydroxy-6,2',3'-trimethoxyflavone; D001688:Biological Products; D005419:Flavonoids; D012709:Serum Albumin