Synthesis, Characterization of a Baicalin-Strontium(II) Complex and Its BSA-Binding Activity

Baicalin is one of the major bioactive constituents of Scutellaria baicalensis Georgi, possessed anti-inflammation, antimicrobial and anticancer activity, has been attained extensive attention. In the present work, a new baicalin-Sr(II) complex (Sr[baic] center dot 3H(2)O) was synthesized to enhance its biological activity. A series of experiments were carried out to give the satisfying reaction conditions: pH=8.3 and the molar ratio of L:M <= 1:1. The obtained complex Sr[baic]center dot 3H(2)O was characterized by IR, ES-MS UV-vis, atomic absorption, elemental analysis and thermogravimetric analysis. The interactions between baicalin/Sr[baic] and bovine serum albumin were also researched through fluorescence spectrum, which accord with the static quenching mechanism, Sr[baic] has higher binding ability than baicalin. Thermodynamic parameters Delta G degrees < 0, Delta H degrees< 0 and Delta S degrees > 0, indicated that electrostatic forces is the major interaction forces in Sr[baic]-bovine serum albumin system. Furthermore, the synchronous fluorescence experiments were carried out. The studies revealed that both baicalin and Sr[baic] quench the intrinsic fluorescence of bovine serum albumin, and the possible binding site is located on Trp residues. In circular dichroism spectrum, the binding of baicalin and Sr [baic] to bovine serum albumin lead to a loss in helical stability, by contrast, Sr[baic] increases baicalin's binding ability.