Synthesis, Characterization and Interaction of Rare Earth Complexes of Rutin with HSA and BSA

The complexes of La, Pr, Gd and Dy rare earth element with rutin were synthesized. On the basis of elemental analysis, thermogravimetric analysis, IR spectra and molar conductance, the general formula of the complexes, NamRELCln·6H2O (L=C27H29O16, RE=La, Pr, n=10, m=8; RE=Gd, n=7, m=5; RE=Dy, n=5, m=3), is given. At the same time, under the imitated physiological pH condition of animal body, the binding of complexes to HSA and BSA was studied by fluorescence spectroscopy. It is shown that this compound has a quite strong ability to quench the fluorescence launching from HSA and BSA. According to Stern-Volmer equation and Scatchard equation, it is found that HSA and BSA have reacted with rutin-Pr and formed two systems: rutin-Pr-HSA and rutin-Pr-BSA, respectively. The quenching belongs to static fluorescence quenching, with non-radiation energy transfer within a molecule. According to Scatchard equation, the binding constants KA (for rutin-Pr-HSA, 295 K: 5.577 × 105 L·mol-1; 310 K: 1.828 × 105 L·mol-1; for rutin-Pr-BSA, 295 K: 2.330 × 105 L·mol-1; 310 K: 7.640 × 104 L·mol-1) and the number of binding sites n (for rutin-Pr-HSA, 295 K: 0.94; 310 K: 1.2; for rutin-Pr-BSA, 295 K: 0.93; 310 K: 1.1); at different temperatures and the thermodynamic parameters (for rutin-Pr-HSA, ΔH=-56.54 kJ·mol-1, 295K: ΔG=-32.45kJ·mol-1 and ΔS=-81.66 J·K-1; 310 K: ΔG=-31.23 kJ·mol-1 and ΔS=-81.65 J·K-1; for rutin-Pr-BSA, ΔH=-56.53 kJ·mol-1, 295 K: ΔG=-30.31 kJ·mol-1 and ΔS=-88.88 J·K-1; 310 K: ΔG=-28.98 kJ·mol-1 and ΔS=-88.87 J·K-1) at correspondence temperatures were obtained. H-bond and Van der Waals are two main reactions between complexes and HSA (BSA). The effect of complexes on the conformation of HSA and BSA was analyzed by circular dichroism (CD) and synchronous fluorescence spectra.