Stereoselective protein binding of ketoprofen: Effect of albumin concentration and of the biological system

Abstract

Equilibrium dialysis was used to study in vitro the enantioselective binding of R, S, and racemic ketoprofen at physiological pH and temperature in human serum albumin (HSA) (1, 20, and 40 g/liter) and in plasma. The binding of enantiomers in a racemic mixture was studied to see the effect of each isomer on the other's interaction with the protein. The free fractions were determined by high-performance liquid chromatography. The binding of ketoprofen enantiomers to albumin was enantioselective, depending on both drug and protein concentrations. Enantioselectivity was observed in plasma too but was the opposite of that in HSA at 40 g/liter. The percentage of each isomer unbound was higher in the racemic mixture than with the isomer alone. The displacement of probes specific for HSA sites I and II, studied by spectrofluorimetry, suggests that all three preparations of ketoprofen are bound mainly to site I and secondarily to site II.

Stereoselective binding of mexiletine and ketoprofen enantiomers with human serum albumin domains

“…Ketoprofen bound extensively to HSA (above 99%) [18] in a stereoselective manner [34] , which may be related to the enantioselective disposition of ketoprofen in vivo [35,36] . Ketoprofen was reported to bind to HSA at site I and site II; the main binding site was site II (the high affinity binding site) in domain III [19][20][21] . In this study, the bound fraction for ketoprofen racemate was in accordance with the results of the study by Matsushita [14] (bound fraction of 64.0%±5.4% for the ketoprofen racemate).…”

“…However, contradictory results have been obtained under different experimental conditions. Dubois et al [19] found that the enantioselective binding of ketoprofen enantiomers to HSA depended on drug and protein concentrations. Enantioselectivity was observed in HSA at 1 g/L, but the opposite enantioselectivity was observed at 40 g/L.…”

“…Contradictory results for the binding of ketoprofen enantiomers to HSA have been obtained in several studies [17,19,24,30] . Zou et al [24] reported that the S-enantiomers bind to HSA more strongly than the R-enantiomers do.…”

“…Zou et al [24] reported that the S-enantiomers bind to HSA more strongly than the R-enantiomers do. According to Dubois et al [19] , R-ketoprofen bound more strongly than S-ketoprofen, whereas Guo et al [31] found that ketoprofen had little stereoselectivity with respect to binding to HSA. The binding of ketoprofen to DOM III showed remarkable stereoselectivity at the concentration of albumin found in plasma (5.2 µmol/mL), as R-ketoprofen exhibited a significantly higher binding affinity than S-ketoprofen (P=0.0209).…”

“…In 1990, Verbeeck et al determined that ketoprofen bound extensively to HSA (above 99%) [18] , and that this binding may be related to the enantioselective disposition of ketoprofen in vivo. In the past several decades, studies on the stereoselective binding of ketoprofen to HSA have reached a consensus that ketoprofen mainly binds to site II of HSA and does so in a stereoselective manner [19][20][21] . However, contradictory stereoselective binding results have been obtained under different experimental conditions [17,18,[22][23][24] .…”