Enantioselective analysis of ibuprofen in human plasma by anionic cyclodextrin-modified electrokinetic chromatography

Investigation of isomerization of dexibuprofen in a ball mill using chiral capillary electrophoresis

Besides the racemate, the S-enantiomer of ibuprofen (Ibu) is used for the treatment of inflammation and pain. Since the configurational stability of S-Ibu in solid state is of interest, it was studied by means of ball milling experiments. For the evaluation of the enantiomeric composition, a chiral CE method was developed and validated according to the ICH guideline Q2(R1). The addition of Mg²⁺ , Ca²⁺ , or Zn²⁺ ions to the background electrolyte (BGE) was found to improve Ibu enantioresolution. Chiral separation of Ibu enantiomers was achieved on a 60.2 cm (50.0 cm effective length) x 75 μm fused-silica capillary using a background electrolyte (BGE) composed of 50 mM sodium acetate, 10 mM magnesium acetate tetrahydrate, and 35 mM heptakis-(2,3,6-tri-O-methyl)-β-cyclodextrin (TM-β-CD) as chiral selector. The quantification of R-Ibu in the mixture was performed using the normalization procedure. Linearity was evaluated in the range of 0.68-5.49% R-Ibu (R² = 0.999), recovery was found to range between 97 and 103%, the RSD of intra- and interday precision below 2.5%, and the limit of quantification for R- in S-Ibu was calculated to be 0.21% (extrapolated) and 0.15% (dilution of racemic ibuprofen), respectively. Isomerization of S-Ibu was observed under basic conditions by applying long milling times and high milling frequencies.

Enantioseparation performance of CNTs as chiral selectors for the separation of ibuprofen isomers: a dispersion corrected DFT study

The enantioseparation of chiral drugs has been of great interest in the modern pharmaceutical industry since the majority of bioorganic compounds are chiral.

Inhibition of aminoacylase 3 protects rat brain cortex neuronal cells from the toxicity of 4-hydroxy-2-nonenal mercapturate and 4-hydroxy-2-nonenal

4-Hydroxy-2-nonenal (4HNE) and acrolein (ACR) are highly reactive neurotoxic products of lipid peroxidation that are implicated in the pathogenesis and progression of Alzheimer's and Parkinson's diseases. Conjugation with glutathione (GSH) initiates the 4HNE and ACR detoxification pathway, which generates the mercapturates of 4HNE and ACR that can be excreted. Prior work has shown that the efficiency of the GSH-dependent renal detoxification of haloalkene derived mercapturates is significantly decreased upon their deacetylation because of rapid transformation of the deacetylated products into toxic compounds mediated by β-lyase. The enzymes of the GSH-conjugation pathway and β-lyases are expressed in the brain, and we hypothesized that a similar toxicity mechanism may be initiated in the brain by the deacetylation of 4HNE- and ACR-mercapturate. The present study was performed to identify an enzyme(s) involved in 4HNE- and ACR-mercapturate deacetylation, characterize the brain expression of this enzyme and determine whether its inhibition decreases 4HNE and 4HNE-mercapturate neurotoxicity. We demonstrated that of two candidate deacetylases, aminoacylases 1 (AA1) and 3 (AA3), only AA3 efficiently deacetylates both 4HNE- and ACR-mercapturate. AA3 was further localized to neurons and blood vessels. Using a small molecule screen we generated high-affinity AA3 inhibitors. Two of them completely protected rat brain cortex neurons expressing AA3 from the toxicity of 4HNE-mercapturate. 4HNE-cysteine (4HNE-Cys) was also neurotoxic and its toxicity was mostly prevented by a β-lyase inhibitor, aminooxyacetate. The results suggest that the AA3 mediated deacetylation of 4HNE-mercapturate may be involved in the neurotoxicity of 4HNE.

Enantioselective Pharmacokinetics of Ibuprofen and Involved Mechanisms

Although dexibuprofen (S-ibuprofen) was marketed in Austria and Switzerland, the racemate at various formulations is still extensively used worldwide, and there are no indications that the racemate will be replaced by the single enantiomer. Thus, elucidation of the characteristics and involved mechanisms of the chiral pharmacokinetics of racemic ibuprofen is of special importance for the understanding of the pharmacological and toxicological consequences, and for prediction of the clinically potential drug interactions and influence of the pathological states. Stereoselective pharmacokinetics and metabolism are common features for chiral nonsteroidal antiinflammatory drugs (NSAIDs) and especially for 2-arylpropionic acid derivatives characterized with a chiral center adjacent to the carboxyl group. Although the enantioselective pharmacokinetic characteristics of different NSAIDs should be treated case by case, they share similar mechanisms underlying the protein binding, metabolism and chiral inversion. Ibuprofen was the most extensively researched drug in terms of chiral characteristics and mechanisms. Therefore, elucidation of the mechanisms derived from research on ibuprofen may provide better understanding and prediction of other chiral drugs. This article attempts to elucidate the chiral pharmacokinetics and involved mechanisms of ibuprofen in comparison with other NSAIDs based on recent developments. Topics on history of ibuprofen, enantioselective analysis method, absorption, protein binding, conventional metabolism, metabolic chiral inversion, gene polymorphism, and biochemical developments were included. It is worth mentioning that some underlying biochemical mechanisms, especially for the metabolic chiral inversion and ethnic differences still remain to be seen. Further research is required to develop human-resourced researching model and to provide more evidence concerning the site of inversion, species variation, CYP450 gene polymorphisms, and biochemical mechanisms.

Enantioselective CE method for pharmacokinetic studies on ibuprofen and its chiral metabolites with reference to genetic polymorphism

A stereospecific CE method was elaborated for the quantification of ibuprofen enantiomers and their major phase I metabolites: 2'-hydroxy-ibuprofen and 2'-carboxy-ibuprofen in plasma and urine. Optimal temperature and pH of BGE were established to obtain complete separation of eight ibuprofen chiral compounds and (+)-S indobufen, applied as an internal standard, during one analytical run. After isolation from biological matrices using SPE on an octadecyl stationary phase, the analytes were separated and resolved up to 10 min in a silica capillary filled with BGE, consisting of heptakis 2,3,6-tri-O-methyl-beta-CD in triethanolamine-phosphate buffer, pH 5.0. Complete enantioseparation of the all analytes confirmed specificity of the method. The calibration curves were linear in the range of 0.1-25.0 mg/L for IBP enantiomers and their chiral metabolites in 0.5 mL of plasma and 1.0-200.0 mg/L in 0.05 mL of urine. Following SPE procedure, recovery of the chiral analytes from the two media was in the ranges of 82-87%, 90-95% and 70-76% for ibuprofen, 2'-hydroxy-ibuprofen and 2'-carboxy-ibuprofen enantiomers, respectively. The validated method was successfully applied in pharmacokinetic investigations of IBP enantiomers as well as free chiral metabolites in reference to the genetic polymorphism of CYP450 2C isoenzymes.

Progress in capillary electrophoresis of biomarkers and metabolites between 2002 and 2005

Biomarker discovery and metabolite research is a fast-growing and extremely important domain not only for the early detection of certain diseases but also for controlling its progress as well as in pharmaceutical investigations. For the analytical separation and identification, CE plays an indisputable role. Capillary systems enhancing different selectivity are applied and connected to different kind of detection systems. As the choice of buffer and its composition is responsible for a successful separation, special emphasis is put on solvent effects in this review. Altogether the most important capillary electrophoretic techniques applied for biomarker and metabolites analysis published between 2002 and 2005 are summarized and discussed.

Sensitive chiral analysis by capillary electrophoresis

In this review, an updated view of the different strategies used up to now to enhance the sensitivity of detection in chiral analysis by CE will be provided to the readers. With this aim, it will include a brief description of the fundamentals and most of the recent applications performed in sensitive chiral analysis by CE using offline and online sample treatment techniques (SPE, liquid-liquid extraction, microdialysis, etc.), on-column preconcentration techniques based on electrophoretic principles (ITP, stacking, and sweeping), and alternative detection systems (spectroscopic, spectrometric, and electrochemical) to the widely used UV-Vis absorption detection.

Pharmacokinetic applications of capillary electrophoresis: A review on recent progress

This article covers recent publications from 2003 to 2005 on the subject of pharmacokinetic applications of CE. Many analytical methods were validated and more importantly, they were shown to have sufficient sensitivities to access pharmacokinetic data on different models. Because of unique advantages, such as simplified sample preparation methods, small sample amount required, high separation power, and speedy analysis, CE-based assays were found to gain popularity not only as a second method but also as a major method for many pharmacokinetic studies.

Optical purity determination of (S)-lbuprofen in tablets by achiral gas chromatography

An optical purity test was indirectly performed on (S)-ibuprofen as its diastereomeric (R)-(+)-1-phenylethylamide derivative using achiral gas chromatography (GC). The method for the determination of trace (R)-ibuprofen (optical impurity), within the range 1.0 to 50 ng, from a racemic ibuprofen standard was linear (r = 0.9997) with acceptable precision (% RSD < or = 5.3) and accuracy (% RE = 0.7 - -3.9). Similar results were obtained with the method validation for the quantification of (S)-ibuprofen within the range 0.1 to 2.0 microg using a (S)-ibuprofen standard. When applied to seven different commercial (S)-ibuprofen products, their optical purities (98.7 - 99.1%) were determined with good precision (% RSD < or = 4.0).

Enantioselective determination of ibuprofen in plasma by high-performance liquid chromatography–electrospray mass spectrometry

The enantioselective analysis of ibuprofen (IBU), a chiral nonsteroidal anti-inflammatory drug, in human plasma was carried out by high-performance liquid chromatography (HPLC)-mass spectrometry (LC-MS-MS). The plasma samples were prepared by liquid-liquid extraction using hexane:ethyl acetate (8:2, v/v). The HPLC chiral resolution of IBU was obtained using a chiral stationary phase based on a tris-(3,5-dimethylphenylcarbamate) amylose derivative, under reversed phase conditions (CHIRALPAK AD-RH column), using a mobile phase consisting of methanol:water (8:2, v/v), containing 0.1% of an aqueous solution of phosphoric acid at pH 2, at a flow rate of 0.6 ml/min. A make-up liquid of 4.5% (w/v) NH(4)OH aqueous solution was used to assure optimum electrospray ionization in the negative mode. The coefficients of variation and deviation from nominal values were lower than 15% for both within- and between-day assays. The quantitation limit was 0.12 microg/ml and the linear range was 0.12-90.0 microg/ml for both enantiomers. The method proved to be suitable for single dose pharmacokinetic studies.