Studies by biointeraction chromatography of binding by phenytoin metabolites to human serum albumin

摘要

Biointeraction studies based on high performance affinity chromatography were used to investigate the binding of human serum albumin (HSA) to two major phenytoin metabolites: 5-(3-hydroxyphenyl)-5-phenylhydantoin (m-HPPH) and 5-(4-hydroxyphenyl)-5-phenylhydatoin (p-HPPH). This was initially examined by conducting self-competition zonal elution experiments in which m-HPPH or p-HPPH were placed in both the mobile phase and injected sample. It was found that each metabolite had a single major binding site on HSA. Competitive zonal elution experiments using, L-tryptophan, warfarin, digitoxin, and cis-clomiphene as site-selective probes indicated that m-HPPH and p-HPPH were interacting with the indolebenzodiazepine site of HSA. The estimated association equilibrium constants for m-HPPH and p-HPPH at this site were 3.2 (+/- 1.2) x 10(3) and 5.7 (+/- 0.7) x 10(3) M-1. respectively. at pH 7.4 and 37 degrees C. Use of these metabolites as competing agents for injections of phenytoin demonstrated that m-HPPH and p-HPPH had direct competition with this drug at the indole-benzodiazepine site. However, the use of phenytoin as a competing agent indicated that this drug had additional negative allosteric interactions on the binding, of these metabolites to HSA. These results a-reed with previous studies on the binding of phenytoin to HSA and its effects on the interactions of HSA with site-selective probes for the indole-benzodiazepine site. (c) 2006 Elsevier B.V. All rights reserved.