Studies On The Interactions Between Serum Albumins And Small Molecules Of Flavonoid Compounds Using Spectral Technology

Serum albumin is the most abundant protein in the circulatory system in the body of man or animal, which stores and carries a plenty of drugs to all place of the body, including endogens and exogens. Studies on the interactions between bioactive small molecules (especially such as drugs) and biomacromolecules (such as serum albumin) are of important reference value for pharmacodynamics and pharmacokinetics,biochemistry, pharmaceutics and clinic medicine, which can provide an important physical parameters and pharmaceuticals standard. Fluorescence spectrum is of high sensitivity, good selectivity, easy controlling and minimum quantity of used reagent, at the meantime, which can gives the messages of the molecular structure and the changes of molecular conformation. In this paper, the interactions between myricetine, chrysin and puerarin and bovine serum albumin using fluorescent spectra, UV-Vis absorption spectra and circular dichroism(CD) spectra were researched,The interaction mechanism,binding constants,thermodynamic binding parameter,separation distance and reaction force between molecules and the effect of the other factors(for instance,pH,ionic strength,metal ion and surfactants et. al)on the interactions were studied in detail. In this essay,the bioactive groups and bioactive sites of drugs were obtained from above conclusions,too. It is worth noting that the conclusions obtained from the researches on the interactions between drugs and protein are of great values on biochemistry ,pharmaceutical chemistry,clinical medicine and pharmaceutical activity。The studies were performed on five ports as such follow.1. The interactions of myricetine, chrysin and puerarin and bovine serum albumin using UV-Vis absorption spectra were researched. According to the changes of the site and intensity of band of system, it was found that the drug-protein complexes were formed between drug and protein. 2. The interactions of myricetine,chrysin and puerarin and bovine serum albumin using fluorescent spectra were studied. It was found that the fluorescence of BSA was efficiently quenched by these drugs by using the protein as an intrinsic fluorescence probe. The binding sites of the drugs in protein were discussed, the binding constants of drugs and BSA and the association force (hydrophobic interactions and electrostatic interactions) and the binding modes were determined between drugs and BSA.3. The key and outbreak point is that the effects of other conditions on the binding were fully investigated such as pH value,ionic strength,metal ion and surfactants. On one hand, the effect of these factors on the associations was observed, on another hand, the binding forces of the association between three flavonoid drugs and BSA were proved once again.4. The change of microenvironment of tryptophan residues in protein and the secondary structure conformation of protein in the absence and presence of three drugs were investigated by using synchronized fluorescence and CD spectra. It was found that the microenvironment of tryptophan residues and contents of alpha helices in the secondary structure of protein were all changed. The polar of microenvironment of tryptophan residues increased, but the hydrophobic decreased. For the binding of Myricetin or Chrysin and protein, contents of alpha helices reduced; while for Puerarin contents of alpha helices increased.5. The another outstand point was especially arranged alone, the apprehensive comparisons of the binding between three flavonoids and BSA on the fluorescence quenching, binding constants, association forces, the effect of pH value and surfactants were discussed, respectively. Then by comparison and analyses on the structure of these drugs, the bioactive groups and sites of these drugs were determined. Hydroxyl groups at the position of 5, 7 of ring A in the three flavonoids were key determining groups, at the same time, the hydroxyl groups of structure B were also important bioactive groups, which are bound to protein by electrostatic interactions. It was also concluded that the ring B is a bioactive group, and the ring B which is a hydrophobic bioactive group is associated with protein by hydrophobic interaction.