Abstract: The interaction between bovine serum albumin(BSA) and berberine chloride(BC) extracted and purified from coptis chinensis franch was studied by using UV and fluorescence spectroscopy. The phenomenon that fluorescence spectra of BSA splitted and shifted from a simple peak to double peaks in the presence of BC was explained, and the double peaks responding to tyrosine and tryptophan residues respectively was prospected. Fluorescence quenching was thought to be deduced by combining static quenching with nonradiative energy transfer. The values of the apparent association constant(K_A) at 30 ℃ and 37 ℃ are 8.66×10⁴ L·mol^-1 and 8.72×10⁴ L·mol^-1 respectively, and the binding sites of BC molecules on BSA(n) are (3.1±0.2). The stereo-distance(r) between BC and fluorescent amino acid residues of the BSA is 3.75 nm at 30 ℃ and 3.62 nm at 37 ℃, which affirms that part of BC segments have inserted into the hydrophobic pockets of BSA. Binding BC to BSA is a spontaneous supramolecular interaction in which entropy increases and Gibbs free energy decreases, and the main driving force of the above interaction is hydrophobic force.

Key words: Fluorescence spectroscopy, Active component of Chinese herbs, Coptis chinensis franch, Berberine chloride, Bovine serum albumin