Two phenylethanoid glycosides, acteoside and forsythoside B, were first isolated from the traditional Chinese herb Callicarpa peii H.T. Chang. The interaction between the two phenylethanoid glycosides and bovine serum albumin (BSA) was investigated by fluorescence, UV-vis absorbance and circular dichroism (CD). The results showed that the quenching mechanism in the drug-BSA binary systems was a combination of static quenching and non-radiative energy transfer. Displacement experiments confirmed that the drug bound to the site I of BSA. UV-vis and CD measurements indicated that the binding of the drug to BSA induced conformational changes in BSA.
Keywords: BSA; Fluorescence quenching; Phenylethanoid glycosides; Site competitive binding.