The interaction on HSA and the antibacterial activity from four polyoxometalate hybrids based on berberine

Four organic-polyoxometalate hybrids BR4[SiW12O40] (BR-SiW), BR3[PMo12O40] (BR-PMo), BR4K[EuSiW11O40]& BULL;2H(2)O (BR-EuSiW) and BR6Na3[EuW10O36] (BR-EuW) were fabricated by the polyoxometalates (POMs) anions and berberine cations (BR) noted for the alkaloids in traditional Chinese herbal medicine. These hybrids have been characterized and confirmed. The interaction between hybrids and human serum albumin (HSA) was investigated in a buffer solution (pH 7.4) using ultraviolet-visible light absorption and fluorescence techniques. The classical Stern-Volmer equation was used to analyze the fluorescence quenching at three temperatures (296, 303 and 310 K), and the static quenching mechanism for interaction was proposed. The Thermodynamic parameters, enthalpy, entropy change, and Gibbs free energy of hybrids interacting on HSA were calculated by Scatchard equation. The results indicated that therewas one binding site on the protein and BR-POMs all showed stronger binding force than that of raw materials. Synchronous fluorescence results showed that the binding sites of BR-POMs and HSA were not effectively affected the surrounding microenvironment. The following antibacterial experiments implied that inhibitory effect of hybrids were synergistic effect from organic active ingredient and POMs but the simple combination. All these data were prepared for further research on biology.