Studies on the antagonistic action between chloramphenicol and quinolones with presence of bovine serum albumin by fluorescence spectroscopy

Chloramphenicol (CHL) and quinolone drugs like ofloxacin (OFLX), lomefloxacin (LMX) and ciprofloxacin (CPFX) can all quench the fluorescence of bovine serum albumin (BSA) in the aqueous solution of pH=7.40. This quenching effect becomes more significant when CHL and quinolone drugs coexist. Based on this, further studies on the interactions between CHL and quinolone drugs using fluorescence spectrum are established. The results showed that the interaction between the drugs would increase the binding constant and binding stability of the drug and protein, thus reducing the amount of drugs transported to their targets. Therefore, free drug concentration at targets would decrease, reducing the efficacy of the drugs. It indicated that there exists antagonistic action between drugs. The results also showed that the quenching mechanism of BSA by the drugs is a static procedure. The number of binding sites is 1 in various systems. Due to the existence of the antagonistic action between drugs, the binding distance r is reduced. Studies utilizing synchronous spectra showed that the antagonistic action between the drugs would affect the conformation of BSA, making protein molecules extend and hydrophobic decrease. The order of antagonistic action between CHL and quinolone drugs is: CPFX > OFLX > LMX with presence of BSA. Crown Copyright (C) 2009 Published by Elsevier B.V. All rights reserved.