warfarin and octanoic-acid

Rat, rabbit and human serum albumins were immobilized on an HPLC stationary phase, and the resulting phases were tested for their abilities to determine the extent and enantioselectivity of ligand binding to the respective albumins. A series of achiral and chiral compounds were chromatographed on the phases including benzodiazepinones, non-steroidal anti-inflammatory drugs, amino acids, warfarin and leucovorin. The chromatographic retentions of the benzodiazepinones and one series of nonsteroidal anti-inflammatory agents were compared with protein binding data from ultrafiltration studies. The observed correlation factors (r) were consistently 0.999, indicating that the albumin phases can be used to determine the magnitude of binding to the respective proteins. The enantioselectivity was also investigated, and the results indicate that the stationary phases can be used to determine relative enantioselectivities and intraspecies differences in this stereoselectivity. For example, when R- and S-warfarin were studied, R-warfarin was retained to a greater extent than S-warfarin by the rabbit serum albumin-stationary phase, whereas the opposite enantioselectivity was found for the rat and human albumins. Binding interaction studies were also conducted on the rabbit and rat albumin stationary phases by sequentially adding increasing concentrations of octanoic acid to the chromatographic mobile phase. The octanoic acid reduced the retention of a series of non-steroidal anti-inflammatory agents, and the results of the experiments suggest that the interaction takes place at two or more sites on the albumin molecule and by anti-cooperative allosteric interactions and competitive displacement. The results of this study demonstrate that the immobilized serum albumin columns can be used to quantitate and probe ligand binding interactions.

Topics: Animals; Anti-Inflammatory Agents, Non-Steroidal; Benzodiazepinones; Binding, Competitive; Caprylates; Chromatography, High Pressure Liquid; Humans; Ligands; Protein Binding; Rabbits; Rats; Serum Albumin; Stereoisomerism; Ultrafiltration; Warfarin

A chiral stationary phase for high-performance liquid chromatography, based upon immobilized human serum albumin (HSA), was used to investigate the effect of octanoic acid on the simultaneous binding of a series of drugs to albumin. Octanoic acid was found to bind with high affinity to a primary binding site, which in turn induced an allosteric change in the region of drug binding Site II, resulting in the displacement of compounds binding there. Approximately 80% of the binding of suprofen and ketoprofen to HSA was accounted for by binding at Site II. Octanoic acid was found to also bind to a secondary site on HSA, with much lower affinity. This secondary site appeared to be the warfarin-azapropazone binding area (drug binding Site I), as both warfarin and phenylbutazone were displaced in a competitive manner by high levels of octanoic acid. The enantioselective binding to HSA exhibited by warfarin, suprofen and ketoprofen was found to be due to differential binding of the enantiomers at Site I; the primary binding site for suprofen and ketoprofen was not enantioselective.

Topics: Allosteric Site; Binding, Competitive; Caprylates; Chromatography, High Pressure Liquid; Humans; Ketoprofen; Oxazepam; Pharmaceutical Preparations; Phenylbutazone; Serum Albumin; Stereoisomerism; Suprofen; Tolbutamide; Warfarin