Applicability of capillary electrophoresis‐frontal analysis for displacement studies: Effect of several drugs on l‐tryptophan and lidocaine binding to human serum albumin

Abstract

The effective concentration of a drug in the blood, i.e. the concentration of a free drug in the blood, is influenced by the strength of drug binding onto plasma proteins. Besides its efficacy, these interactions subsequently influence the liberation, absorption, distribution, metabolism, excretion, and toxicological properties of the drug. It is important to not only determine the binding strength and stoichiometry, but also the binding site of a drug on the plasma protein molecule, because the co-administration of drugs with the same binding site can affect the above-mentioned concentration and as a result the pharmacological behavior of the drugs and lead to side effects caused by the change in free drug concentration, its toxicity. In this study, the binding characteristics of six drugs with human serum albumin, the most abundant protein in human plasma, were determined by capillary electrophoresis-frontal analysis, and the obtained values of binding parameters were compared with the literature data. The effect of several drugs and site markers on the binding of l-tryptophan and lidocaine to human serum albumin was investigated in subsequent displacement studies which thus demonstrated the usability of capillary electrophoresis as an automated high-throughput screening method for drug-protein binding studies.

Enantioresolution and Binding Affinity Studies on Human Serum Albumin: Recent Applications and Trends

“…Table 5 showed different studies that have been reported over the years for the evaluation of the binding affinity of HSA of numerous drugs and other bioactive compounds using CE techniques. Many studies focused on the individual binding parameters for each compound/enantiomer [153,155,161] while others also described competitive studies between compounds to the binding sites of HSA [156,157,159]. Furthermore, most of these studies were enantioselective studies where the differences in binding of each enantiomer of the analyzed compounds to HSA were evaluated and compared using, many of them, HSA as a chiral selector [150,152,154,155].…”

“…The results showed that the (S)-amlodipine binds to HSA more strongly (0.902-1.04 × 10 5 M −1 ) than its antipode (0.991-1.12 × 10 4 M −1 ) [151]. CE-FA was also used to study the binding of L-tryptophan and lidocaine to HSA as well as the effect of several drugs on the binding affinity through displacement studies [159]. A decrease in the bound of L-tryptophan was observed in the presence of the other drugs indicating that these molecules share the same binding site while no difference was observed for lidocaine [159].…”

“…CE-FA was also used to study the binding of L-tryptophan and lidocaine to HSA as well as the effect of several drugs on the binding affinity through displacement studies [159]. A decrease in the bound of L-tryptophan was observed in the presence of the other drugs indicating that these molecules share the same binding site while no difference was observed for lidocaine [159]. Additionally, this technique was used to evaluate the binding of nuarimol, methoxatin disodium salt and captopril to HSA [152,156,157].…”

“…Additionally, this technique was used to evaluate the binding of nuarimol, methoxatin disodium salt and captopril to HSA [152,156,157]. All these studies described the several advantages of CE-FA such as simplicity, flexibility, high speed and the possibility to use near physiological conditions [151,152,156,157,159].…”

“…Regarding the pH, as previously mentioned for the HPALC studies, most CE studies were also performed using a pH of 7.4. However, some exceptions were observed and pH ranging from 6.0 to 8.5 were also reported [151,159,160]. In addition, although the physiological temperature is considered to be around 37 • C, only two studies used this temperature [156,157].…”