No description available.

The design, synthesis and evaluation of chiral selectors that allow the determination of enantiomeric composition using electrospray ionization mass spectrometry are detailed herein. The enantiomers of the chiral selector were mass labeled at a distant site from the chiral recognition sites of the molecules. The mass-labeled enantiomers were mixed in a one-to-one ratio to form a quasi-racemate. Chiral recognition can be observed by comparing relative abundances of the pseudo-diastereomeric selector-analyte complexes in the mass spectrum. The observed sense of chiral recognition with mass spectrometry was consistent with that observed chromatographically using a corresponding chiral stationary phase in every case. The complex intensity fraction (CIF, intensity of one selector-analyte complex divided by the sum of the intensities for both selector-analyte complexes) is linear with the enantiomeric composition. The slope of this line is an indication of the extent of the enantioselectivity: the larger the slope, the more significant the enantioselectivity. In addition, this line can be used as a calibration curve for the quantitative determination of enantiomeric composition of the same analyte with unkown enantiomeric composition. Amide derivatives of DNB-amino acids were first used as pseudo-enantiomeric chiral selectors in the presence of added lithium chloride. The enantioselectivity values were smaller than those observed on chiral HPLC using the corresponding chiral stationary phase. The use of deprotonated DNB-amino acids as chiral selectors provides higher enantioselectivities, but with low ion abundances. Tertiary amine appended analogues of the chiral stationary phase DNB-Leucine were prepared. The amine was appended to provide a site for ready ionization (through protonation). The performance of chiral selectors of this type was compared to the original chiral selectors that lack this functional group. Chiral recognition was also observed in a reciprocal sense using proline-derived pseudo-enantiomeric chiral selectors and analytes similar to DNB-amino acid esters or amides. Optimization of the electrospray ionization conditions provided similar enantioselectivities to those from chiral HPLC. Libraries of tertiary amine appended derivatives of DNB-dipeptides, which were prepared through combinatorial peptide synthesis, were screened using electrospray ionization mass spectrometry. The use of electrospray ionization mass spectrometry as a discovery tool for new chiral selectors is discussed.

A maioria dos medicamentos normalmente prescritos são comercializados sob a forma racêmica, apesar de se ter conhecimento que a presença de diferentes enantiômeros em uma formulação farmacêutica pode levar a diferentes atividades farmacológicas, farmacocinéticas e perfis toxicológicos. O uso de enantiômeros puros em formulações farmacêuticas pode resultar em melhor ajuste de dose e diminuição dos efeitos adversos, fato que torna estudos a respeito de quiralidade de moléculas fundamental na área farmacêutica. Atualmente, os métodos analíticos mais empregados para a separação e determinação da pureza enantiomérica de compostos são a CLAE-FEQ e eletroforese capilar com seletores quirais. Os enantiômeros de esmolol foram separados através de CLAE-FEQ em fase reversa utilizando coluna Chiralcel-OD-RH (250 x 4,6 mm d.i.), 5 µm. A fase móvel foi composta por perclorato de potássio 100 mM, pH 2,08 : acetonitrila : dietilamina (80:20:0,2) com vazão de 0,5 mL.min-1 e detecção a 220 nm. Os enantiômeros de esmolol também foram separados através de CLAE-FEQ em fase normal utilizando coluna Chiralcel-OD (250 x 4,6 mm d.i.), 10 µm. A fase móvel foi composta por hexano : etanol : dietilamina (75:25:0,2) com vazão de 1,0 mL.min-1 e detecção a 220 nm. Ambos os métodos foram validados, sendo possível considerá-los precisos, seletivos, específicos, exatos e lineares para quantificar os enantiômeros de esmolol em medicamentos. Os testes realizados com cloridrato de sotalol por CLAE não indicaram separação enantiomérica ao serem utilizadas coluna Chiralcel OD®, Chiralcel OD-RH®, Burke e Whelk®. Os ensaios realizados por eletroforese capilar apresentaram separação parcial dos enantiômeros de sotalol e de esmolol, porém houve ausência de reprodutibilidade do método. / Most commonly prescribed drugs are marketed as racemic mixtures, even though it is well known that the presence of different enantiomers in a pharmaceutical formulation can lead to different pharmacological, pharmacokinetic and toxicological profiles. The use of pure enantiomers in pharmaceutical formulations can result in better dose adjustment and reduction of side effects, fact which makes studies on molecular chirality important to the pharmaceutical area. Currently, high performance liquid chromatography using chiral stationary phases (CSPs) and capillary electrophoresis with chiral selectors are the most commonly methods employed for the separation and determination of enantiomeric purity of compounds. The enantiomers of esmolol were separated through HPLC using a reversed phase CSP column Chiralcel-OD-RH (250 x 4,6 mm i.d.) 5 µm. The mobile phase was composed of 100 mM potassium perchlorate, pH 2,08 : acetonitrile: diethylamine (80:20:0,2) at a flow rate of 0,5 mL.min-1 and detection at 220 nm. The enantiomers of esmolol were also separated using HPLC-CSP using normal phase column Chiralcel OD (250 x 4,6 mm i.d.), 10 µm. The mobile phase consisted of hexane : ethanol : diethylamine (75:25:0,2) with a flow rate of 1,0 mL.min-1 and detection at 220 nm. Both methods were validated, and it was possible to consider them precise, selective, specific, exact and linear to quantify the enantiomers of esmolol on drugs. HPLC tests conducted with sotalol indicated no enantiomeric separation when Chiralcel OD, Chiralcel OD-RH, Burke and Whelk columns were used. Capillary electrophoresis tests showed partial separation of the enantiomers of sotalol and esmolol, but there was lack of reproducibility.

A duloxetina é um potente inibidor duplo da recaptação de serotonina e norepinefrina, disponível como enantiômero puro, sob a forma S-duloxetina e comercializado como pellets em cápsulas. O R enantiômero da duloxetina é também um inibidor da recaptação, no entanto, este é menos potente que seu isômero, sendo considerado como impureza enantiomérica. Este trabalho teve como objetivos o desenvolvimento e a validação de métodos analíticos para o controle de qualidade da duloxetina e de sua respectiva impureza enantiomérica por cromatografia líquida de alta eficiência (CLAE), e por eletroforese capilar (EC). A resolução dos enantiômeros da duloxetina foi realizada a partir da utilização de fase estacionária quiral, baseada celulose, por CLAE. A separação por EC foi desenvolvida a partir da utilização de hidroxipropil-β-ciclodextrina (HPβCD) como seletor quiral. A validação dos métodos foi efetuada de acordo com os guias de validação disponíveis na literatura e os métodos propostos foram considerados específicos, lineares, precisos, exatos e robustos. A análise comparativa entre os métodos desenvolvidos demonstrou não haver diferença estatisticamente significativa na quantificação do enantiômero S-duloxetina. / Duloxetine is a double potent inhibitor of serotonin and norepinephrine reuptake, available as a pure enantiomer, in the S-duloxetine form and marketed as pellets into capsules. The R enantiomer of duloxetine is also an inhibitor of reuptake, however, less potent and being considered enantiomeric impurity. This work aimed the development and validation of analytical methods for quality control of duloxetine and its respective enantiomeric impurity by high performance liquid chromatography (HPLC) and capillary electrophoresis (CE). The resolution of the enantiomers of duloxetine was performed with the use of chiral stationary phase, based on cellulose, by HPLC. The separation by CE was developed with the use of hydroxypropyl-β-cyclodextrin (HPβCD) as chiral selector. The method validation was performed according to the guides available in the literature and the proposed methods were considered specific, linear, precise, accurate and robust. The comparative analysis between the methods developed showed no statistically significant difference in the quantification of S-duloxetine enantiomer.

A maioria dos medicamentos normalmente prescritos são comercializados sob a forma racêmica, apesar de se ter conhecimento que a presença de diferentes enantiômeros em uma formulação farmacêutica pode levar a diferentes atividades farmacológicas, farmacocinéticas e perfis toxicológicos. O uso de enantiômeros puros em formulações farmacêuticas pode resultar em melhor ajuste de dose e diminuição dos efeitos adversos, fato que torna estudos a respeito de quiralidade de moléculas fundamental na área farmacêutica. Atualmente, os métodos analíticos mais empregados para a separação e determinação da pureza enantiomérica de compostos são a CLAE-FEQ e eletroforese capilar com seletores quirais. Os enantiômeros de esmolol foram separados através de CLAE-FEQ em fase reversa utilizando coluna Chiralcel-OD-RH (250 x 4,6 mm d.i.), 5 µm. A fase móvel foi composta por perclorato de potássio 100 mM, pH 2,08 : acetonitrila : dietilamina (80:20:0,2) com vazão de 0,5 mL.min-1 e detecção a 220 nm. Os enantiômeros de esmolol também foram separados através de CLAE-FEQ em fase normal utilizando coluna Chiralcel-OD (250 x 4,6 mm d.i.), 10 µm. A fase móvel foi composta por hexano : etanol : dietilamina (75:25:0,2) com vazão de 1,0 mL.min-1 e detecção a 220 nm. Ambos os métodos foram validados, sendo possível considerá-los precisos, seletivos, específicos, exatos e lineares para quantificar os enantiômeros de esmolol em medicamentos. Os testes realizados com cloridrato de sotalol por CLAE não indicaram separação enantiomérica ao serem utilizadas coluna Chiralcel OD®, Chiralcel OD-RH®, Burke e Whelk®. Os ensaios realizados por eletroforese capilar apresentaram separação parcial dos enantiômeros de sotalol e de esmolol, porém houve ausência de reprodutibilidade do método. / Most commonly prescribed drugs are marketed as racemic mixtures, even though it is well known that the presence of different enantiomers in a pharmaceutical formulation can lead to different pharmacological, pharmacokinetic and toxicological profiles. The use of pure enantiomers in pharmaceutical formulations can result in better dose adjustment and reduction of side effects, fact which makes studies on molecular chirality important to the pharmaceutical area. Currently, high performance liquid chromatography using chiral stationary phases (CSPs) and capillary electrophoresis with chiral selectors are the most commonly methods employed for the separation and determination of enantiomeric purity of compounds. The enantiomers of esmolol were separated through HPLC using a reversed phase CSP column Chiralcel-OD-RH (250 x 4,6 mm i.d.) 5 µm. The mobile phase was composed of 100 mM potassium perchlorate, pH 2,08 : acetonitrile: diethylamine (80:20:0,2) at a flow rate of 0,5 mL.min-1 and detection at 220 nm. The enantiomers of esmolol were also separated using HPLC-CSP using normal phase column Chiralcel OD (250 x 4,6 mm i.d.), 10 µm. The mobile phase consisted of hexane : ethanol : diethylamine (75:25:0,2) with a flow rate of 1,0 mL.min-1 and detection at 220 nm. Both methods were validated, and it was possible to consider them precise, selective, specific, exact and linear to quantify the enantiomers of esmolol on drugs. HPLC tests conducted with sotalol indicated no enantiomeric separation when Chiralcel OD, Chiralcel OD-RH, Burke and Whelk columns were used. Capillary electrophoresis tests showed partial separation of the enantiomers of sotalol and esmolol, but there was lack of reproducibility.

<p>Delivery of drugs to the brain requires passage across the blood-brain barrier (BBB). Both for drugs already on the market and for new drugs under development, it is important to know to what extent a drug enters the CNS. Many drugs used clinically are racemic mixtures, <i>i.e.</i> equal parts of the (<i>S</i>)- and (<i>R</i>)-enantiomers. </p><p>The present studies focus on the enantiomers and racemates of a number of 5-HT_1A receptor agonists and antagonists (pindolol, propranolol, 8-OH-DPAT and other 8-substituted-2-(di-<i>n</i>-propylamino)tetralin derivatives) and BBB transport <i>in vitro</i> and distribution to the brain <i>in vivo.</i> Assays (HPLC-based) were set up or developed for determination of the racemates and the pure enantiomers (chiral column) of drugs in plasma and brain tissue. BBB transport was assessed <i>in vitro</i> using bovine brain endothelial cells cocultured with rat astrocytes. The physicochemical constants (log P, pKa) and plasma protein binding were determined. Pindolol, propranolol and several tetralines accumulated over time in brain tissue. For pindolol and propranolol, but not for most tetralins, the distribution to the brain was stereoselective, (<i>S</i>)>(<i>R</i>). Pretreatment with verapamil, an inhibitor of drug efflux <i>via</i> P-glycoprotein, differentially decreased the brain/plasma ratios of the enantiomers of pindolol and propranolol, indicating that verapamil may also inhibit an influx transport mechanism. <i>In vitro</i> results with racemic pindolol, propranolol and tetralins showed no differences in BBB transport between the enantiomers. A more rapid apical to basolateral transport (influx) <i>vs</i>. the basolateral to apical (efflux) transport of propranolol (not pindolol) and most tetralins <i>in vitro</i> indicated active transport across the BBB. </p><p>In conclusion, the combined <i>in vivo</i> and <i>in vitro</i> results are consistent with active transport of the studied compounds across the BBB rather than passive diffusion due to their lipophilicity. Some, but not all, chiral drugs are stereoselectively distributed to the brain. Stereoselective plasma protein binding or stereoselective transport across brain endothelial cells does not seem to explain the stereoselective accumulation of pindolol and propranolol. The stereochemical configuration of compounds contributes to their pharmacokinetic as well as their pharmacodynamic uniqueness. The characteristics of the enantiomers of chiral compounds need to be determined empirically rather than based on generalizations from structural or physicochemical information.</p>

Delivery of drugs to the brain requires passage across the blood-brain barrier (BBB). Both for drugs already on the market and for new drugs under development, it is important to know to what extent a drug enters the CNS. Many drugs used clinically are racemic mixtures, i.e. equal parts of the (S)- and (R)-enantiomers. The present studies focus on the enantiomers and racemates of a number of 5-HT1A receptor agonists and antagonists (pindolol, propranolol, 8-OH-DPAT and other 8-substituted-2-(di-n-propylamino)tetralin derivatives) and BBB transport in vitro and distribution to the brain in vivo. Assays (HPLC-based) were set up or developed for determination of the racemates and the pure enantiomers (chiral column) of drugs in plasma and brain tissue. BBB transport was assessed in vitro using bovine brain endothelial cells cocultured with rat astrocytes. The physicochemical constants (log P, pKa) and plasma protein binding were determined. Pindolol, propranolol and several tetralines accumulated over time in brain tissue. For pindolol and propranolol, but not for most tetralins, the distribution to the brain was stereoselective, (S)&gt;(R). Pretreatment with verapamil, an inhibitor of drug efflux via P-glycoprotein, differentially decreased the brain/plasma ratios of the enantiomers of pindolol and propranolol, indicating that verapamil may also inhibit an influx transport mechanism. In vitro results with racemic pindolol, propranolol and tetralins showed no differences in BBB transport between the enantiomers. A more rapid apical to basolateral transport (influx) vs. the basolateral to apical (efflux) transport of propranolol (not pindolol) and most tetralins in vitro indicated active transport across the BBB. In conclusion, the combined in vivo and in vitro results are consistent with active transport of the studied compounds across the BBB rather than passive diffusion due to their lipophilicity. Some, but not all, chiral drugs are stereoselectively distributed to the brain. Stereoselective plasma protein binding or stereoselective transport across brain endothelial cells does not seem to explain the stereoselective accumulation of pindolol and propranolol. The stereochemical configuration of compounds contributes to their pharmacokinetic as well as their pharmacodynamic uniqueness. The characteristics of the enantiomers of chiral compounds need to be determined empirically rather than based on generalizations from structural or physicochemical information.

A duloxetina é um potente inibidor duplo da recaptação de serotonina e norepinefrina, disponível como enantiômero puro, sob a forma S-duloxetina e comercializado como pellets em cápsulas. O R enantiômero da duloxetina é também um inibidor da recaptação, no entanto, este é menos potente que seu isômero, sendo considerado como impureza enantiomérica. Este trabalho teve como objetivos o desenvolvimento e a validação de métodos analíticos para o controle de qualidade da duloxetina e de sua respectiva impureza enantiomérica por cromatografia líquida de alta eficiência (CLAE), e por eletroforese capilar (EC). A resolução dos enantiômeros da duloxetina foi realizada a partir da utilização de fase estacionária quiral, baseada celulose, por CLAE. A separação por EC foi desenvolvida a partir da utilização de hidroxipropil-β-ciclodextrina (HPβCD) como seletor quiral. A validação dos métodos foi efetuada de acordo com os guias de validação disponíveis na literatura e os métodos propostos foram considerados específicos, lineares, precisos, exatos e robustos. A análise comparativa entre os métodos desenvolvidos demonstrou não haver diferença estatisticamente significativa na quantificação do enantiômero S-duloxetina. / Duloxetine is a double potent inhibitor of serotonin and norepinephrine reuptake, available as a pure enantiomer, in the S-duloxetine form and marketed as pellets into capsules. The R enantiomer of duloxetine is also an inhibitor of reuptake, however, less potent and being considered enantiomeric impurity. This work aimed the development and validation of analytical methods for quality control of duloxetine and its respective enantiomeric impurity by high performance liquid chromatography (HPLC) and capillary electrophoresis (CE). The resolution of the enantiomers of duloxetine was performed with the use of chiral stationary phase, based on cellulose, by HPLC. The separation by CE was developed with the use of hydroxypropyl-β-cyclodextrin (HPβCD) as chiral selector. The method validation was performed according to the guides available in the literature and the proposed methods were considered specific, linear, precise, accurate and robust. The comparative analysis between the methods developed showed no statistically significant difference in the quantification of S-duloxetine enantiomer.

A duloxetina é um potente inibidor duplo da recaptação de serotonina e norepinefrina, disponível como enantiômero puro, sob a forma S-duloxetina e comercializado como pellets em cápsulas. O R enantiômero da duloxetina é também um inibidor da recaptação, no entanto, este é menos potente que seu isômero, sendo considerado como impureza enantiomérica. Este trabalho teve como objetivos o desenvolvimento e a validação de métodos analíticos para o controle de qualidade da duloxetina e de sua respectiva impureza enantiomérica por cromatografia líquida de alta eficiência (CLAE), e por eletroforese capilar (EC). A resolução dos enantiômeros da duloxetina foi realizada a partir da utilização de fase estacionária quiral, baseada celulose, por CLAE. A separação por EC foi desenvolvida a partir da utilização de hidroxipropil-β-ciclodextrina (HPβCD) como seletor quiral. A validação dos métodos foi efetuada de acordo com os guias de validação disponíveis na literatura e os métodos propostos foram considerados específicos, lineares, precisos, exatos e robustos. A análise comparativa entre os métodos desenvolvidos demonstrou não haver diferença estatisticamente significativa na quantificação do enantiômero S-duloxetina. / Duloxetine is a double potent inhibitor of serotonin and norepinephrine reuptake, available as a pure enantiomer, in the S-duloxetine form and marketed as pellets into capsules. The R enantiomer of duloxetine is also an inhibitor of reuptake, however, less potent and being considered enantiomeric impurity. This work aimed the development and validation of analytical methods for quality control of duloxetine and its respective enantiomeric impurity by high performance liquid chromatography (HPLC) and capillary electrophoresis (CE). The resolution of the enantiomers of duloxetine was performed with the use of chiral stationary phase, based on cellulose, by HPLC. The separation by CE was developed with the use of hydroxypropyl-β-cyclodextrin (HPβCD) as chiral selector. The method validation was performed according to the guides available in the literature and the proposed methods were considered specific, linear, precise, accurate and robust. The comparative analysis between the methods developed showed no statistically significant difference in the quantification of S-duloxetine enantiomer.

No description available.