Sensitive derivatizatton reagents for the resolution of carboxylic acid enantiomers by high-performance liquid chromatography

Resolution of chiral drugs by liquid chromatography based upon diastereomer formation with chiral derivatization reagents

Chiral derivatization reagents for resolution of biologically important compounds, such as chiral drugs by high-performance liquid chromatography (HPLC), based upon pre-column derivatization and diastereomer formation, are reviewed. The derivatization reagents for various functional groups, i.e., amine, carboxyl, carbonyl, hydroxyl and thiol, are evaluated in terms of reactivity, stability, wavelength, handling, versatility, sensitivity, and selectivity. The applicability of the reagents to the analyses of drugs and bioactive compounds are included in the text.

Configuration and racemization determination of cysteine residues in peptides by chiral derivatization and HPLC: application to oxytocin peptides

An improved RP-HPLC method was developed for the determination of the configuration and stereochemical purity of cysteine residues in peptides. The method consists of oxidation of cysteine and cystine residues to cysteic acid, followed by hydrolysis and pre-column chiral derivatization with Val-Marfey's reagent.

Chiral derivatization reagents for drug enantioseparation by high-performance liquid chromatography based upon pre-column derivatization and formation of diastereomers: enantioselectivity and related structure

Structures and related enantioselectivities of the respective chiral derivatization reagents (CDRs) for drug enantioseparation by high-performance chromatography based upon pre-column derivatization and diastereomeric formation are reviewed. The elution order of diastereomers caused reaction of some CDRs with enantiomeric amino acids and carboxylic acids. The development of new CDRs available for indirect HPLC methods is also discussed. (c) 2001 John Wiley & Sons, Ltd.

Resolution of enantiomers of ibuprofen by liquid chromatography: a review

Ibuprofen is one of the most effective and widely used non-steroidal analgesic and anti-inflammatory agent. It is marketed as a racemic mixture though it is known that the pharmacological activity resides in the (S)-(+)-enantiomer only. Several direct/indirect liquid chromatographic methods involving a variety of chiral/achiral phases along with their possible role in resolution, chiral and achiral agents used for derivatisation have been discussed with special reference to ibuprofen, and mentioning their application to the resolution of other 2-aryl-propionic acids/profens.

Chiral separation of pharmaceuticals possessing a carboxy moiety

The separation of carboxylic enantiomers in the pharmaceutical field using high-performance liquid chromatographic and capillary electrophoretic techniques is reviewed. The techniques used for chiral separation include diastereomer derivatization, a chiral mobile phase, a chiral stationary phase (high-performance liquid chromatography) and chiral additives (capillary electrophoresis). Practical and conventional separation systems for pharmaceutical applications, such as pharmacokinetics, optical purity testing and stability studies, are described. A comprehensive collection of applications to carboxylic drugs and other carboxylic compounds of pharmaceutical interest is listed in the tables. The characteristics of each enantioseparation method are also discussed briefly.

1-(5-Dimethylamino-1-naphthalenesulphonyl)-(S)-3-aminopyrrolidine (DNS-Apy) as a fluorescence chiral labelling reagent for carboxylic acid enantiomers

1-(5-Dimethylamino-1-naphthalenesulphonyl)-(S)-3-aminopyrrolidi ne (DNS-Apy) has been synthesized for the separation of carboxylic acid enantiomers by high-performance liquid chromatography (HPLC) and sensitive detection. The reagent reacts with carboxylic acids at room temperature in the presence of activation agents 2,2'-dipyridyl disulphide (DPDS) and triphenylphosphine (TPP). The maximum emission of the diastereomeric amide derived from (S)-phenylpropionic acid and ketoprofen derivatives of DNS-Apy was at 530 nm with excitation at 340 nm. The emission wavelength shifted towards the blue and the fluorescence intensities increased with increasing acetonitrile concentration in the medium. The diastereomers derived from anti-inflammatory drugs were efficiently resolved with a reverse-phase column using water:acetonitrile mixture as mobile phase. All of the racemate of arylpropionic acid derivatives gave equal fluorescence intensity of the two enantiomers with the exception of ketoprofen derivatives where the intensity of the first eluting enantiomer was half that of the second.

Methods of analysis of chiral non-steroidal anti-inflammatory drugs

Although the analysis of the enantiomers of chiral non-steroidal anti-inflammatory drugs (NSAIDs) has been carried out for over 20 years, there often remains a deficit within the pharmaceutical and medical sciences to address this issue. Hence, despite world-wide therapeutic use of chiral NSAIDs the importance of stereoselectivity in pharmacokinetic, pharmacodynamic and pharmacological activity and disposition has often been ignored. This review presents both the general principles that allow separation of chiral NSAID enantiomers, and discusses both the advantages and disadvantages of the available chromatographic assay methods and procedures used to separately quantify NSAID enantiomers in biological matrices.

Recent progress in liquid chromatographic enantioseparation based upon diastereomer formation with fluorescent chiral derivatization reagents

Techniques for the resolution by liquid chromatography of racemic compounds based upon diastereomer formation with a fluorescent chiral reagent are outlined in this review. The tagging reagents for various functional groups, i.e. amine, carboxyl, hydroxyl and thiol, are evaluated in terms of optical purity, handling, flexibility, stability, sensitivity and selectivity. The applicabilities of the reagents to drugs and biologically important substances are included in the text. This review is limited to reagents with fluorophores and reagents that exhibit fluorescence.

Automated precolumn fluorescence labelling by carbodiimide activation of N-acetylaspartate and N-acetylaspartylglutamate applied to an HPLC brain tissue analysis

An automated method is described to couple carboxyl-containing metabolites to the fluorophore 2-aminoanthracene in aqueous solution (containing 75% methanol) in the presence of N,N-dicyclohexylcarbodiimide. The reaction was optimized for N-acetylaspartate (N-Ac-Asp) and N-acetylaspartylglutamate (N-Ac-Asp-Glu). The reactions occurred within 5 min at room temperature in the presence of 0.5-2 mM HCl. At concentrations of electrolytes exceeding 10 mM the coupling reaction became suboptimal. Derivatization was performed in a commercial precolumn derivatization unit. Additional tubing was needed to provide the reagents prior to reversed-phase HPLC and fluorescence detection. The assay is linear over at least three orders of magnitude; as little as 1 pmol could reproducibly be assayed in 100 micrograms wet weight brain tissue extracted with a mixture of methanol and 4 mM HCl (9:1, v/v). N-Ac-Asp and N-Ac-Asp-Glu levels in several brain regions and spinal cord were similar to those so far reported. The compounds could not be detected in peripheral tissue. The advantages, prospects and limitations of the present approach over existing methods to estimate water-soluble carboxylic acids is discussed.

High-performance liquid chromatographic determination of cortolic and cortolonic acids as pyrenyl ester derivatives

A new procedure is described for the detection of the acidic metabolites of cortisol (cortoic acids) as the pyrenylmethyl-21-oic esters. The derivatizing reagent, diazomethylpyrene, was prepared by an improved procedure. The reagent was used at room temperature, required no catalyst, and was not restricted by stoichiometric requirements. The steroid esters were separated by reversed-phase high-performance liquid chromatography and analyzed simultaneously by their ultraviolet absorbance and fluorescence characteristics. Identities of the products were confirmed using the photodiode array detector to determine spectral profiles, absorbance maxima, and absorbance ratios. Further confirmation of identity of the cortoic acid esters used mass spectrometry under normal and collision-activated dissociation conditions. With the method described, a linear spectral response was obtained between 8 and 1680 fmol. Application of the technique to the analysis of steroid acids in human urine indicated the presence of cortoic acids.

Rapid and sensitive high-performance liquid chromatographic assay of tiaprofenic acid enantiomers in human plasma and urine

A sensitive stereospecific high-performance liquid chromatographic assay of tiaprofenic acid (TA) enantiomers in human plasma and urine was developed. The biological specimens are acidified, and the drug and internal standard, (+/-)-2-(4-benzoylphenyl)butyric acid, extracted with an isooctane-isopropanol (95:5) mixture (plasma) or chloroform (urine), followed by sequential reaction of the enantiomers with trichloroethyl chloroformate and L-leucinamide. The reactions were complete at ambient temperature in less than 3 min. The diastereoisomers of TA and internal standard were then extracted into chloroform. The organic layer was evaporated, and the reconstituted residue chromatographed at ambient temperature on a C18 reversed-phase column with a mobile phase consisting of 0.06 M monopotassium phosphate-acetonitrile-triethylamine (65:35:0.02) at a flow-rate of 1 ml/min. The TA diastereoisomers were detected at 310 nm, free of interfering peaks, with a resolution factor of 2.1. Within the examined plasma and urine enantiomeric concentration ranges of 0.2-20 and 10-100 mg/l, respectively, an excellent linear relationship was obtained between the peak-area ratios and the corresponding concentrations. The assay was reproducible and sufficiently accurate to be applied to the stereoselective pharmacokinetic analysis of TA enantiomers in plasma and urine following administration of therapeutic doses of the drug.

Enantiomeric separation of amino acids by micro high-performance liquid chromatography on an L-proline-bonded stationary phase

Enantiomeric separation of amino acids on an L-proline-bonded phase was examined in micro high-performance liquid chromatography. Gradient separation of seven pairs of racemic dansyl amino acids was achieved by connecting chiral and hydrophobic columns in series.

Profiling of amino acids in body fluids and tissues by means of liquid chromatography

The needs of urgent diagnoses and the needs emerging from acute forms of diseases have directed progress in amino acid profiling to modern, rapid, automated analyses that can be done at reasonable cost. The first step in this direction was the short programmes of classical ion-exchange chromatography. At the beginning of this review we attempted to survey methods of sample preparation and sample treatment, as these are frequently neglected stages where artefacts or erroneous results may arise. There are basically the following approaches in amino acid profiling by liquid chromatographic techniques. For preliminary screening of a large number of samples in clinical routine planar procedures are the methods of choice, as they allow large numbers of samples to be handled with minimum effort and at very reasonable cost. For more precise profiling, particularly where quantitative data are essential, one can choose between some of the modern procedures for separating underivatized amino acids using modern equipment for cation-exchange chromatography, by making use of a stepped series of lithium citrate buffers with ninhydrin, o-phthalaldehyde or 4-fluoro-7-nitrobenzo-2,1,3-oxadiazole detection. Ninhydrin detection is preferred in those situations where the demands on sensitivity are not high. Where, however, only small amounts of samples are available or high sensitivity is required, one of the latter two methods is preferred. The o-phthalaldehyde procedure is not suitable for the detection of secondary amines and, if these are of interest, then diazole derivatization is to be preferred. At present, however, the ninhydrin and o-phthalaldehyde detection procedures are the most popular. The other choice is to use one of the sophisticated HPLC systems equipped with fluorescence detection and to separate amino acids as derivatives. Here o-phthalaldehyde and 4-fluoro-7-nitrobenzo-2,1,3-oxadiazole derivatives offer the most versatile possibilities. Automation and computerization have penetrated both categories of liquid column separation and are applied to automated sample delivery, automated and computerized gradient formation and quantitation of the data obtained. The tables of metabolic disorders of amino acids and the roles of different amino acids in these disorders should provide preliminary information for clinical chemists.

Column liquid chromatography for the simultaneous determination of the enantiomers of loxoprofen sodium and its metabolites in human urine

A method for simultaneously quantitating the enantiomers in the alpha-substituted propionic acid moiety of loxoprofen and its two monohydroxy metabolites, trans- and cis-alcohols, by column liquid chromatography was described. Loxoprofen and its metabolites were readily converted to the amides by condensation with a chiral reagent (1S)-1-(4-dimethyl-aminonaphthalen-1-yl) ethylamine. The diastereoisomers were separated on a normal-phase column with n-hexane-ethylacetate (68:32) as a mobile phase and detected with a fluorescence detector. The established method was applied to the determination of the enantiomers of these compounds in the urine of human subjects having received loxoprofen sodium. The results indicated that the three compounds were largely composed of the (2S)-isomer, in accordance with previous findings in rats.