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Enantioseparation of the newly synthesized series of novel quinoline-2(1H)-one epoxide structures rac-6a–c and rac-8a–c, named marinoepoxides, is described. Marinoepoxide rac-6a, the key intermediate in the total synthesis of natural products marinoaziridines A and B, as well as their structural analogues, was synthesized by addition of the achiral ylide generated in situ from the sulfonium salt 5 or 7, to the carbon-oxygen double bond of the corresponding quinoline-2(1H)-one-4-carbaldehyde 4a–c in good yield. Separation of enantiomers of (±)-2,3,3-trisubstituted marinoepoxides rac-6a–c and (±)-trans-2,3-disubstituted marinoepoxides rac-8a–c was studied using two immobilized polysaccharide type chiral stationary phases (CSPs); tris-(3,5-dichlorophenylcarbamoyl)cellulose stationary phase (CHIRAL ART Cellulose-SC) and tris-(3,5-dimethylphenylcarbamoyl)amylose stationary phase (CHIRAL ART Amylose-SA). Enantioseparation conditions were explored by high-performance liquid chromatography (HPLC) using dimethyl carbonate/alcohol mixtures and n-hexane/ethanol (80/20, v/v) as mobile phase, and by supercritical fluid chromatography (SFC) using CO2/alcohol mixtures as mobile phase. In all examined racemates, enantioseparation was successfully achieved, but its efficiency largely depended on the structure of chiral selector and type/composition of the mobile phase.

This manuscript presents the development, validation and application of a multi-residue supercritical fluid chromatography coupled with tandem mass spectrometry method for the analysis of 140 chiral and non-chiral chemicals of emerging concern in environmental samples, with 81 compounds being fully quantitative, 14 semi-quantitative and 45 qualitative, validated according to European Medicine Agency (EMA) guidelines (European Medicines Agency 2019). One unified LC-MS method was used to analyse all analytes, which were split into three injection methods to ensure sufficient peak resolution. The unified method provided an average of 113% accuracy and 4.5% precision across the analyte range. Limits of detection were in the range of 35 pg L−1–0.7 μg L−1, in both river water and wastewater, with an average LOD of 33 ng L−1. The method was combined with solid-phase extraction and applied in environmental samples, showing very good accuracy and precision, as well as excellent chromatographic resolution of a range of chiral enantiomers including beta-blockers, benzodiazepines and antidepressants. The method resulted in quantification of 75% of analytes in at least two matrices, and 56% in the trio of environmental matrices of river water, effluent wastewater and influent wastewater, enabling its use in monitoring compounds of environmental concern, from their sources of origin through to their discharge into the environment. Electronic supplementary material The online version of this article (10.1007/s00216-020-02780-9) contains supplementary material, which is available to authorized users.

17β-Hydroxysteroid dehydrogenase type 3 (17β-HSD3) is expressed at high levels in testes and seminal vesicles; it is also present in prostate tissue and involved in gonadal and non-gonadal testosterone biosynthesis. The enzyme is membrane-bound, and a crystal structure is not yet available. Selective aryl benzylamine-based inhibitors were designed and synthesised as potential agents for prostate cancer therapeutics through structure-based design, using a previously built homology model with docking studies. Potent, selective, low nanomolar IC50 17β-HSD3 inhibitors were discovered using N-(2-([2-(4-chlorophenoxy)phenylamino]methyl)phenyl)acetamide (1). The most potent compounds have IC50 values of approximately 75 nM. Compound 29, N-[2-(1-Acetylpiperidin-4-ylamino)benzyl]-N-[2-(4-chlorophenoxy)phenyl]acetamide, has an IC50 of 76 nM, while compound 30, N-(2-(1-[2-(4-chlorophenoxy)-phenylamino]ethyl)phenyl)acetamide, has an IC50 of 74 nM. Racemic C-allyl derivative 26 (IC50 of 520 nM) was easily formed from 1 in good yield and, to determine binding directionality, its enantiomers were separated by chiral chromatography. Absolute configuration was determined using single crystal X-ray crystallography. Only the S-(+)-enantiomer (32) was active with an IC50 of 370 nM. Binding directionality was predictable through our in silico docking studies, giving confidence to our model. Importantly, all novel inhibitors are selective over the type 2 isozyme of 17β-HSD2 and show

The interaction between human serum albumin (HSA) and apremilast (APR), a novel antipsoriatic drug, was characterized by multimodal analytical techniques including high-performance liquid chromatography (HPLC), fluorescence spectroscopy and molecular docking for the first time. Using an HSA chiral stationary phase, the APR enantiomers were well separated, indicating enantioselective binding between the protein and the analytes. The influence of chromatographic parameters—type and concentration of the organic modifier, buffer type, pH, ionic strength of the mobile phase, flow rate and column temperature—on the chromatographic responses (retention factor and selectivity) was analyzed in detail. The results revealed that the eutomer S-APR bound to the protein to a greater extent than the antipode. The classical van ’t Hoff method was applied for thermodynamic analysis, which indicated that the enantioseparation was enthalpy-controlled. The stability constants of the protein–enantiomer complexes, determined by fluorescence spectroscopy, were in accordance with the elution order observed in HPLC (KR-APR-HSA = 6.45 × 103 M−1, KS-APR-HSA = 1.04 × 104 M−1), showing that, indeed, the later-eluting S-APR displayed a stronger binding with HSA. Molecular docking was applied to study and analyze the interactions between HSA and the APR enantiomers at the atomic level. It was revealed that the most favored APR binding occurred at the border between domains I and II of HSA, and secondary interactions were responsible for the different binding strengths of the enantiomers.

The β-blocker (S)-betaxolol has been synthesized in 99% enantiomeric excess (ee) from the commercially available precursor 4-(2-hydroxyethyl)phenol. The racemic chlorohydrin 1-chloro-3-(4-(2-(cyclopropylmethoxy)ethyl)phenoxy)propan-2-ol was esterified with vinyl acetate catalyzed by lipase B from Candida antarctica, which gave the R-chlorhydrin (R)-1-chloro-3-(4-(2-(cyclopropylmethoxy)ethyl)phenoxy)propan-2-ol in 99% ee with 38% yield. The enantiomeric excess of the R-chlorohydrin was retained in an amination reaction with isopropylamine in methanol to yield (S)-betaxolol in 99% ee and with 9% overall yield. We are under way to improve the yield.

Two minor phospholipids, i.e., mono- and/or dimethylphosphatidylethanolamines, are widespread in many organisms, from bacteria to higher plants and animals. A molecular mixture of methyl-PE and dimethyl-PE was obtained from total lipids by liquid chromatography and further identified by mass spectrometry. Total methyl-PE and dimethyl-PE were cleaved by phospholipase C, and the resulting diacylglycerols, in the form of acetyl derivatives, were separated into alkyl-acyl, alkenyl-acyl, and diacylglycerols. Reversed-phase LC/MS allowed dozens of molecular species to be identified and further analyzed. This was performed on a chiral column, and identification by tandem positive ESI revealed that diacyl derivatives from all four bacteria were mixtures of both R and S enantiomers. The same applied to alkenyl-acyl derivatives of anaerobic bacteria. Analysis thus confirmed that some bacteria biosynthesize phospholipids having both sn-glycerol-3-phosphate and sn-glycerol-1-phosphate as precursors. These findings were further supported by data already published in GenBank. The use of chiral chromatography made it possible to prove that both enantiomers of glycerol phosphate of some molecular species of mono- and dimethylphosphatidylethanolamines are present. The result of the analysis can be interpreted that the cultured bacteria do not have homochiral membranes but, on the contrary, have an asymmetric, i.e., heterochiral membranes.

During the last years, supercritical fluid chromatography (SFC) has attracted a continuously growing number of users. Thanks to the introduction of state-of-the-art equipment, this technique has allowed to run three-to-five times faster separations than in high-performance liquid chromatography (HPLC) on columns packed with particles of comparable dimension, at lower pressure drops and without loss of efficiency. Thanks to its high versatility, its high-throughput screening capability, and “green” character of the mobile phase, SFC has become particularly attractive for the separation of chiral drugs in pharmaceutical industries. In this review, we will consider the latest applications of SFC for the analysis of compounds of pharmaceutical interest and/or with biological activity essentially covering main achievements of the last 3 years. We also focus on some very recent, remarkable applications of SFC in ultrafast enantioseparations on chiral columns of the latest generation. Technical improvements needed on commercial equipment to increase the competitiveness of SFC towards highly efficient enantioseparations are discussed.

Hemp and cannabis industry is undergoing a renewed interest due to legalization of marijuana (a topic that all countries are discussing, especially in recent years) and the growing importance of therapeutic properties of cannabinoids. Together with an increment in the production of hemp and recreational cannabis, there has been an increasing demand for accurate potency testing of products (i.e. quantification of main cannabinoids present in the plant in terms of weight percentage) prior commercialization. This translates in an urgent need of reliable analytical methods to characterize cannabis and hemp samples. Cannabis and hemp preparations are commercialized under various forms (e.g., flowers, oils, candies or even baked goods) usually containing a large number of often very similar compounds making their separation very challenging. Strictly connected to this, another emerging topic concerns the need for the developing of large scale separation techniques for the purification of cannabinoids from complex matrices and for the preparation of analytical-grade standards (including the chiral ones). This paper reviews the most recent achievements in both these aspects. Cutting-edge applications and novel opportunities in potency testing by high performance liquid chromatography (HPLC) with UV detection (which is becoming the golden standard, according to several pharmacopeias, for this kind of measurements) are discussed. The focus has been given to the very important topic of enantio-discrimination of chiral cannabinoids, for which supercritical fluid chromatography (SFC) appears to be particularly suitable. The last part of the work covers the purification of cannabinoids through preparative chromatography. In this regard, particular attention has been given to the most innovative multi-column techniques allowing for the continuous purification of target molecules. The most recent advancements and future challenges in this field are discussed.

The issue of drug chirality is attracting increasing attention among the scientific community. The phenomenon of chirality has been overlooked in environmental research (environmental occurrence, fate and toxicity) despite the great impact that chiral pharmacologically active compounds (cPACs) can provoke on ecosystems. The aim of this paper is to introduce the topic of chirality and its implications in environmental contamination. Special attention has been paid to the most recent advances in chiral analysis based on liquid chromatography coupled with mass spectrometry and the most popular protein based chiral stationary phases. Several groups of cPACs of environmental relevance, such as illicit drugs, human and veterinary medicines were discussed. The increase in the number of papers published in the area of chiral environmental analysis indicates that researchers are actively pursuing new opportunities to provide better understanding of environmental impacts resulting from the enantiomerism of cPACs.

Chiral discrimination has become one of the most important fields in analytical and medicinal chemistry, and forensic toxicology. The enantiomers may have different binding to proteins that may lead to many pharmacological and toxicological differences between them, including kinetic (at the absorption, distribution, metabolism and excretion level) or dynamic (level of potency and efficacy or even differences in mechanism of action) variations. Cathinone derivatives are chiral compounds, sold via the internet for recreational use, and little is known about their enantiomeric selectivity. Consequently, it is of crucial importance for the development of resolution methods to obtain pure enantiomers to study their biological effects. In the last few years, techniques for chiral drug analysis, as chromatography, have been developed and some works related to the analytical enantiomeric resolution of synthetic cathinones were described. However, information about synthetic cathinones in the literature is scarce specially concerning single enantiomers. In this mini-review, analytical chiral resolution and biological differences between enantiomers of cathinone derivatives will be addressed. © The Author 2017. Published by Oxford University Press. All rights reserved. Acknowledgments: Bárbara Silva thanks to the Universidade do Porto/FMUP through FSE—Fundo Social Europeu, NORTE2020—Programa Operacional Regional do Norte, no âmbito da operação NORTE-08-5369-FSE-000011—Programas Doutorais for her PhD grant. Funding: This work received financial support from the European Union (FEDER funds POCI/01/0145/FEDER/07728) and National funds (FCT/MEC, Fundação para a Ciência e a Tecnologia and Ministério da Educação e Ciência) under the Partnership Agreement PT2020 UID/MULTI/04378/2013 and UID/Multi/ 04423/2013 Comissão de Coordenação e Desenvolvimento Regional do Norte (CCDRN)/NORTE2020/Portugal 2020 through the project: DESignBIOtecHealth—New Technologies for three Health Challenges of Modern Societies: Diabetes, Drug Abuse and Kidney Diseases) for its financial support.

A reinvestigation of the monoterpene chromane ester enriched fraction from Peperomia obtusifolia usingchiral chromatography led to the identification of a minor peak, which was elucidated by NMR and HRMSas fenchyl-3,4-dihydro-5-hydroxy-2,7-dimethyl-8-(3 00 -methyl-2 00 -butenyl)-2-(4 0 -methyl-1 0 ,3 0 -pentadie-nyl)-2H-1-benzopyran-6-carboxylate, the same structure assigned to two other fenchyl esters describedpreviously, pointing out a stereoisomeric relationship among them. Further NMR analysis revealed that itwas actually a mixture of two compounds, whose absolute configurations were determined by VCD mea-surements. Although, almost no vibrational transitions could be assigned to the chiral chromane, theexperimental VCD spectrum was largely opposite to that obtained for the average experimental VCD[(2S,1 000 R,2 000 R,4 000 S +2R,1 000 R,2 000 R,4 000 S)/2] for fenchol derivatives. These results allowed us to assign theputa-tive compounds as a racemic mixture of the chiral chromane esterified with the monoterpene (1S,2S,4R)-fenchol, which had not been identified in our early work. 2012 Elsevier Ltd. All rights reserved.

Background Clopidogrel is used in at-risk infants to prevent thrombotic complications. There is no commercially available liquid preparation and existing formulations have not been evaluated for the chiral stability of clopidogrel. Aim To determine the stability of clopidogrel 1 mg/mL liquid formulations using chiral chromatography. Method Clopidogrel 1 mg/mL suspension was formulated using Plavix (clopidogrel) tablets and Ora-Plus:Ora-Sweet 1:1, and stored at room temperature and under refrigeration. Samples were also prepared using a variety of co-solvents and stored at room temperature. Samples were taken for up to 49 days and assayed for S-clopidogrel, R-clopidogrel and S-acid using high-performance chiral liquid chromatography. Percentage of S-clopidogrel remaining (at least 90% of nominal content) and percentage of degradation product formation were used to estimate shelf-life. Results Only the refrigerated Ora-Plus:Ora-Sweet mixture did not have degradation products that exceeded USP limits for clopidogrel impurities for at least 30 days. The estimated shelf-lives of the Ora-Plus:Ora-Sweet mixtures at room temperature (25 °C) and under refrigeration (4 °C) were 19 and 37.5 days, respectively. There was no improvement in stability when mixtures were prepared using a variety of co-solvents. Conclusion Clopidogrel 1 mg/mL suspension made with Ora-Plus:Ora-Sweet and stored in amber glass bottles was stable for 1 month under refrigeration and 2 weeks at room temperature.

Clenbuterol is a &beta, 2-agonist used in the veterinary treatment of asthma in several countries. The drug is listed on the World Antidoping Agency&rsquo, s prohibited list due to its effect on increased protein synthesis in the body. However, racemic clenbuterol has recently been shown to reduce the risk of Parkinson&rsquo, s disease. In order to reveal which one (or both) of the enantiomers that cause this effect, pure enantiomers need to be separately studied. (R)-1-(4-Amino-3,5-dichlorophenyl)-2-bromoethan-1-ol has been synthesised in 93% enantiomeric excess (ee) by asymmetric reduction of the corresponding ketone catalysed by a ketoreductase and nicotinamide adenine dinucleotide phosphate (NADPH) as the cofactor in dimethyl sulfoxide (DMSO). (S)-N-(2,6-Dichloro-4-(1-hydroxyethyl)phenyl)acetamide has been synthesised in &gt, 98% ee by the same system. Both synthons are potential precursors for clenbuterol enantiomers.

The natural-like assessment of essential oils is a demanding task due to the growing trend toward adulterations. Usually chiral chromatography was used for this purpose due to the capability of assessing stereospecificity which is directly related to the enzymatic pathways of each plant species. On the other hand, the quality of an essential oil involves also the evaluation of its oxidative state, mainly connected with the age and storage conditions. In fact, some modifications in the chemical profile of the oil can occur if not properly preserved. Alterations of the components due to oxidative reactions lead to the formation of peroxides, endoperoxides and epoxides, such as ascaridole and 1,2,4-trihydroxymenthane, usually present in very low amount, formed by the oxidation of terpinen-4-ol and α-terpinene, respectively. Therefore, in the present research, the quality of Australian Tea Tree oil (Melaleuca alternifolia (Maiden & Betche) Cheel, Myrtaceae) was investigated by means of a multi heart-cut multidimensional gas chromatographic system coupled to a mass spectrometer detector and by conventional enantio-GC. The MDGC system allowed the complete separation of the compounds of interest transferred from the first column to a second dimension based on a different separation mechanism. The MS detector at the end of the second column provided the identification of the peaks with high similarity values because of their high purities after the multidimensional separation. Method validation was carried out, in order to use this procedure for routine application, monitoring the repeatability of 1D retention times and 2D peak areas, LoD and LoQ. Finally, enantiomeric ratios for chiral compounds were established to support quality data obtained.

Brush-type chiral stationary phase CSP 12 was specifically designed for separation of BINAPO enantiomers, which can be useful as organocatalysts or as chiral ligands in organometallic catalysis. This chromatographic separation process can compete with other routes to enantiomerically pure BINAPO.

Clobazam, a 1,5-benzodiazepin-2,4-dione, is a chiral molecule because its ground state conformation features a nonplanar seven-membered ring lacking reflection symmetry elements. The two conformational enantiomers of clobazam interconvert at room temperature by a simple ring-flipping process. Variable temperature HPLC on the Pirkle type (R)-N-(3,5-dinitronenzoyl)phenylglycine and (R,R)-Whelk-O1 chiral stationary phases (CSPs) allowed us to separate for the first time the conformational enantiomers of clobazam and to observe peak coalescence-decoalescence phenomena due to concomitant separation and interconversion processes occurring on the same time scale. Clobazam showed temperature dependent dynamic high-performance liquid chromatography (HPLC) profiles with interconversion plateaus on the two CSPs indicative of on-column enantiomer interconversion. (enantiomerization) in the column temperature range between Tcol = 10°C and Tcol = 30°C, whereas on-column interconversion was absent at temperature close to or lower than Tcol = 5°C. Computer simulation of exchange-deformed HPLC profiles using a program based on the stochastic model yielded the apparent rate constants for the on-column enantiomerization and the corresponding free energy activation barriers. At Tcol = 20°C the averaged enantiomerization barriers, ΔG(‡), for clobazam were found in the range 21.08-21.53 kcal mol(-1) on the two CSPs. The experimental dynamic chromatograms and the corresponding interconversion barriers reported in this article are consistent with the literature data measured by DNMR at higher temperatures and in different solvents.

A Bakerbond ODS column was dynamically coated with the chiral selector N τ -n- decyl - l - histidine , and then loaded with copper(II) ions. A number of racemic mixtures of underivatized amino acids were resolved on such a column via chiral ligand-exchange chromatography. The most important experimental parameters influencing column efficiency, retention and selectivity (eluent flow-rate, analyte concentration, temperature and mobile phase composition) were extensively investigated. Results are discussed in light of CLEC theory and thermodynamic data on model systems in aqueous solution. The most likely structures for the stationary ternary complex are suggested.

Made available in DSpace on 2014-06-11T19:35:08Z (GMT). No. of bitstreams: 0 Previous issue date: 2010-03-19Bitstream added on 2014-06-13T19:05:20Z : No. of bitstreams: 1 rinaldo_d_dr_araiq.pdf: 1188120 bytes, checksum: 1e4f3603501a8b454e918390b4c81bce (MD5) Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Este trabalho abordou a determinação quali e quantitativa de enantiômeros de catequinas em extratos e infusões das folhas de espécies do gênero Byrsonima (Malpighiaceae), tais como: B.basiloba, B. cocolobifolia, B. crassa, B. intermedia e B. verbascifolia. O trabalho descreve a determinação rápida e eficiente de catequina, ent- catequina, epicatequina e ent-epicatequina por cromatografia líquida de alta eficiência acoplada a detector de arranjo de fotodiodos e dicrísmo circular, usando coluna de fase estaconária quiral. O método possui alta seletividade e permite identificar inequivocadamente diastereômeros de catequinas em matrizes complexas como extratos vegetais, com limites de detecção (0,42 a 0,77 μg mL-1 ) e quantificação (1,27 a 2,32 μg mL-1 ) satisfatórios para as condições analisadas, e valores de precisão (0,3 to 4,8%) e exatidão (70,0 a 110,2%) recomendados pela ANVISA. Com exceção da espécie B. intermedia, quatro espécies do gênero apresentaram em seus extratos e infusões os diastereômeros catequina, epicatequina e ent-epicatequina. Experimentos para avaliar a epimerização da catequina indicaram que a incomum ent-epicatequina não é um artefato, podendo ser um produto do metabolismo de espécies do gênero Byrsonima. Enantiômeros da catequina apresentam diferentes atividades farmacológicas, o que pode causar a ocorrência de efeitos colaterais diversos, danosos à saúde humana. Portanto, esses resultados podem alertar quanto ao consumo indiscriminado de plantas medicinais pela população e contribuir para criação de políticas mais rigorosas no controle de qualidade de fitoterápicos no Brasil This work deals with the qualitative and quantitative determination of catechin and epicatechin enantiomers both in extracts and infusions from the leaves of the Byrsonima (Malpighiaceae) species (B.basiloba, B. cocolobifolia, B. crassa, B. intermedia and B. verbascifolia). This work describes a simple and reliable analytical high performance liquid chromatographic (HPLC) method coupled with photodiode array detector and circular dichroism for simultaneous determination of catechin, ent-catechin, epicatechin and ent-epicatechin. The direct separation was obtained in normal phase by HPLC using chiral stationary phase. The method has high selectivity. Regardless of variations in retention time, it was possible to identify unequivocally the enantiomers of catechin and epicatechin in complex matrices like plant extracts with satisfactory limit of detection (0.42 to 0.77 μg mL-1 ) and limite of quantification (1.27 to 2.32 μg mL-1 ). Under the conditions used, precision values were 0.3 to 4.8%, whereas accuracy values were 75.0 to 110.2%, recommended by ANVISA. Aside from B. intermedia specie, the other four Byrsonima species presented catechin, epicatechin and ent-epicatechin diastereomers both in methanolic extract and infusions. Experiments were carried out for verification the possibility of catechin epimerization. It was observed that the unusual ent- epicatechin was not an artifact, but product of Byrsonima species metabolism. Enantiomers of catechin present dissimilar pharmacological activities, which may cause the occurrence of various side effects, harmful to human health. Therefore, these results may warn about the indiscriminate use of medicinal plants by the population and contribute to the quality control of Brazilian herbal medicines

The Quantitative Structure Retention Relationship (QSRR) modeling techniques are employed for prediction of retention behavior of chiral secondary alkylaromatic and alkylheterocyclic alcohols, derivatives of 1-phenylethanol, separated on Chiracel OB-H column. Genetic algorithms and neural networks are used to obtain models predicting Retention Order Index (ROI) (R(2) - 0.99), selectivity ROI log alpha (R(2) - 0.93) as well as retention factors (log k) for two types of mobile phases (90/10 and 85/15 n-hexane/isopropanol--R(2) - 0.97 and 0.95). Additionally, a model that predicts log k for both mobile phase in function of i-PrOH concentration is developed (R(2) - 0.97). HOMO energy turns out to be the most important parameter in description of log k while mixed steric-electrostatic interactions with chiral OH group and furan ring are responsible for the chiral recognition. The models are used to assess the stereoselectivity of ethylbenzene dehydrogenase (EBDH), which catalyzes stereospecific syntheses of the investigated compounds. The high stereoselectivity of the enzyme is confirmed but reversion of EBDH enantioselectivity is predicted to take place in the biosynthesis of 1-[1,1'-biphenyl]-4-ylethanol.

Netobimin (NTB) was administered orally to ewes at 20 mg/kg bodyweight. Blood and faecal samples were collected from 1 to 120 h post-treatment and analysed by high-performance liquid chromatography (HPLC). Using a chiral phase-based HPLC, plasma disposition of albendazole sulphoxide (ABZSO) enantiomers produced was also determined. Neither NTB nor albendazole (ABZ) was present and only ABZSO and albendazole sulphone (ABZSO(2)) metabolites were detected in the plasma samples. Maximum plasma concentrations (C(max)) of ABZSO (4.1 +/- 0.7 microg/ml) and ABZSO(2) (1.1 +/- 0.4 microg/ml) were detected at (t(max)) 14.7 and 23.8 h, respectively following oral administration of netobimin. The area under the curve (AUC) of ABZSO (103.8 +/- 22.8 (microg h)/ml) was significantly higher than that ABZSO(2)(26.3 +/- 10.1 (microg h)/ml) (p0.01). (-)-ABZSO and (+)-ABZSO enantiomers were never in racemate proportions in plasma. The AUC of (+)-ABZSO (87.8 +/- 20.3 (microg h)/ml) was almost 6 times larger than that of (-)-ABZSO (15.5 +/- 5.1 (microg h)/ml) (p0.001). Netobimin was not detected, and ABZ was predominant and its AUC was significantly higher than that of ABZSO and ABZSO(2), following NTB administration in faecal samples (p0.01). Unlike in the plasma samples, the proportions of the enantiomers of ABZSO were close to racemic and the ratio of the faecal AUC of (-)-ABZSO (172.22 +/- 57.6 (microg h)/g) and (+)-ABZSO (187.19 +/- 63.4 (microg h)/g) was 0.92. It is concluded that NTB is completely converted to ABZ by the gastrointestinal flora and absorbed ABZ is completely metabolized to its sulphoxide and sulphone metabolites by first-pass effects. The specific behaviour of the two enantiomers probably reflects different enantioselectivity of the enzymatic systems of the liver that are responsible for sulphoxidation and sulphonation of ABZ.

Midodrine hydrochloride is a peripheral alpha(1)-adrenoreceptor agonist that induces venous and arterial vasoconstriction. Midodrine, after oral or intravenous administration, undergoes enzymatic hydrolysis and releases deglymidodrine, a pharmacologically active metabolite. Midodrine and deglymidodrine have a chiral carbon in the 2-position. To investigate the bioactivity of racemates and enantiomers of the drug and metabolite, three chromatographic chiral stationary phases, Chiralcel OD-H, Chiralcel OD-R, and alpha(1)-AGP, were evaluated for enantiomeric resolution. Good enantioseparation of midodrine racemate was obtained using the Chiralcel OD-H column. This stationary phase was then used to collect separately the midodrine enantiomers. By alkaline hydrolysis of rac-midodrine and each separated enantiomer, rac-deglymidodrine and its enantiomers were prepared. The control of the enantiomeric purity was carried out by alpha(1)-AGP stationary phase, while the hydrolysis of rac-midodrine and its enantiomers was controlled by capillary electrophoresis using trimethyl-beta-cyclodextrin as chiral selector. The pharmacological activity of the two racemates and the two enantiomeric pairs was tested in vitro on a strip of rabbit descending thoracic aorta. The tests continued that the activity of the drug and metabolite is due only to the (-)-enantiomer because neither of the (+)-enantiomers is active.