Binding of berberine to bovine serum albumin: spectroscopic approach.

Fluorescence spectroscopy in combination with UV-vis absorption spectroscopy was employed to investigate the binding of an important traditional medicinal herb berberine to bovine serum albumin (BSA) under the physiological conditions. In the mechanism discussion, it was proved that the fluorescence quenching of BSA by berberine is a result of the formation of berberine-BSA complex. Fluorescence quenching constants were determined using the Stern-Volmer equation and Scatchard equation to provide a measure of the binding affinity between berberine and BSA. The results of thermodynamic parameters ΔG, ΔH, ΔS at different temperatures indicate that the electrostatic interactions play a major role for berberine-BSA association. Site marker competitive experiments indicated that the binding of berberine to BSA primarily took place in site II. Furthermore, the Effect of supramolecules to berberine-BSA system, and the distance r between donor (BSA) and acceptor (berberine) was obtained according to fluorescence resonance energy transfer (FRET).