SPECTROSCOPIC INVESTIGATION OF THE BINDING INTERACTIONS OF NEW BERBERINE DERIVATIVES WITH BOVINE SERUM ALBUMIN

In this study, the binding interactions between bovine serum albumin (BSA) and the berberine derivatives A4, B4, and berberine (BBR) were determined using fluorescence spectra and ultraviolet (UV)-vis spectra. The results indicated that the fluorescence of BSA was strongly quenched by the binding of BBR derivatives to BSA. The quenching mechanism of the BBR derivatives was static according to the Stern-Volmer equation. The thermodynamic parameters implied that the interaction process was spontaneous and electrostatic interactions played an important role. According to Forster’s nonradioactive energy transfer theory, the binding distances between BSA and A4, B4, and BBR, were 3.38 nm, 3.27 nm, and 3.53 nm, respectively. The binding ability of B4 to BSA is the strongest among the tested BBR derivatives. Site marker competitive experiments indicated that the binding of BBR derivatives to BSA primarily took place at site II. Our data demonstrate that these fluorescence-quenching methods can be used to rapidly and sensitively determine the binding interactions between BBR derivatives and BSA.