RESUMO
Amiodarone and mexiletine are used for ventricular arrhythmias, for which a combination therapy of both anti-arrhythmic drugs (AADs) is not uncommon. Therapeutic drug monitoring (TDM) can be beneficial for clinical guidance of therapy, especially to correctly identify adverse events. Desethylamiodarone, the active metabolite of amiodarone, accumulates over time and is associated with serious adverse events. Therefore, simultaneous TDM for amiodarone, desethylamiodarone and mexiletine is advantageous in clinical practice. The presented LC-MS/MS method was validated for selectivity, matrix effect, linearity, accuracy, precision, carry-over and stability. The method was continuously evaluated during eight months of clinical use. The method was shown to be linear within the measured range of 0.1 to 10 mg/L for each component. The matrix effect was considered negligible. No interfering responses were found for amiodarone, desethylamiodarone and the isotopic-labeled internal standards. A constant and reproducible within-run contribution of 45.3 %, originating from the system, was identified for mexiletine. The systemic contribution to the peak area of the lowest quantifiable concentration of mexiletine affected the selectivity and carry-over effect measurements. Multiple measurements showed that regression adjusted concentrations were accurate and reproducible, indicating calibration correction was applicable. Sample stability was found to be within limits for all storage conditions and freeze-thaw cycles. Furthermore, long-term method evaluation with external controls resulted in stable measurements with a percentage coefficient of variance between 1.3 % and 6.3 %. The presented practical and reliable method is applicable for clinical TDM and will allow clinical practitioners to guide drug therapy of amiodarone and mexiletine.
Assuntos
Amiodarona , Mexiletina , Espectrometria de Massas em Tandem , Amiodarona/sangue , Amiodarona/análogos & derivados , Humanos , Espectrometria de Massas em Tandem/métodos , Mexiletina/sangue , Mexiletina/análogos & derivados , Mexiletina/química , Reprodutibilidade dos Testes , Cromatografia Líquida/métodos , Modelos Lineares , Monitoramento de Medicamentos/métodos , Antiarrítmicos/sangue , Antiarrítmicos/farmacocinética , Limite de Detecção , Estabilidade de Medicamentos , Sensibilidade e EspecificidadeRESUMO
In the United States, approximately one million individuals are hospitalized every year for arrhythmias, making arrhythmias one of the top causes of healthcare expenditures. Mexiletine is currently used as an antiarrhythmic drug but has limitations. The purpose of this work was to use normal and Long QT syndrome Type 3 (LQTS3) patient-derived human induced pluripotent stem cell (iPSC)-derived cardiomyocytes to identify an analog of mexiletine with superior drug-like properties. Compared to racemic mexiletine, medicinal chemistry optimization of substituted racemic pyridyl phenyl mexiletine analogs resulted in a more potent sodium channel inhibitor with greater selectivity for the sodium over the potassium channel and for late over peak sodium current.
Assuntos
Doença do Sistema de Condução Cardíaco/patologia , Células-Tronco Pluripotentes Induzidas/química , Síndrome do QT Longo/patologia , Mexiletina/farmacologia , Miócitos Cardíacos/patologia , Canal de Sódio Disparado por Voltagem NAV1.5/metabolismo , Piridinas/farmacologia , Relação Dose-Resposta a Droga , Humanos , Mexiletina/química , Estrutura Molecular , Piridinas/química , Relação Estrutura-AtividadeRESUMO
Chiron approach was used to acquire optically pure (R)- and (S)-1-(2,6-dimethylphenoxy)propan-2-ol, immediate precursors of (S)- and (R)-mexiletines, respectively. Two different routes were followed from a D-mannitol-derived optically pure common precursor to get the enantiomeric alcohols separately. Comparison of their specific rotation values with the corresponding literature values as well as exact mirror-image relationship between their CD curves proved their high enantiopurity. These alcohols were then transformed to the corresponding amine-drugs in an efficient one-step process instead of two steps described in the literature.
Assuntos
Manitol/química , Mexiletina/química , Estrutura Molecular , EstereoisomerismoRESUMO
Active pharmaceutical ingredients (APIs) can be prepared in many different solid forms and phases that affect their physicochemical properties and suitability for oral dosage forms. The development and commercialization of dosage forms require analytical techniques that can determine and quantify the API phase in the final drug product. 13C solid-state NMR (SSNMR) spectroscopy is widely employed to characterize pure and formulated solid APIs; however, 13C SSNMR experiments on dosage forms with low API loading are often challenging due to low sensitivity and interference from excipients. Here, fast magic angle spinning 1H SSNMR experiments are shown to be applicable for the rapid characterization of low drug load formulations. Diagnostic 1H SSNMR spectra of APIs within tablets are obtained by using combinations of frequency-selective saturation and excitation pulses, two-dimensional experiments, and 1H spin diffusion periods. Selective saturation pulses efficiently suppress the broad 1H SSNMR signals from the most commonly encountered excipients such as lactose and cellulose, allowing observation of high-frequency API 1H NMR signals. 1H SSNMR provides a 1-3 orders of magnitude reduction in experiment time compared to standard 13C SSNMR experiments, enabling diagnostic SSNMR spectra of dilute APIs within tablets to be obtained within minutes. The 1H SSNMR spectra can be used for quantification, provided calibrations are performed on a standard sample with known API loading.
Assuntos
Isótopos de Carbono/química , Espectroscopia de Ressonância Magnética Nuclear de Carbono-13/métodos , Composição de Medicamentos , Hidrogênio/química , Celulose/química , Excipientes/química , Estudos de Viabilidade , Lactose/química , Mexiletina/química , Ácidos Esteáricos/química , Comprimidos/química , Teofilina/química , Difração de Raios XRESUMO
The human Ether-a-go-go Related Gene (hERG) potassium channel plays a central role in the rapid component (IKr) of cardiac action potential repolarization phase. A large number of structurally different compounds block hERG and cause a high risk of arrhythmias. Among the drugs that block hERG channel, a few compounds have been identified as hERG channel activators. Such compounds may be useful, at least in theory, for the treatment of long term QT syndrome. Here we describe a new activator of hERG channel, named MC450. This compound is a symmetric urea, derived from (R)-mexiletine. Using patch-clamp recordings, we found that MC450 increased the activation current of hERG channel, with an EC50 of 41±4µM. Moreover MC450 caused a depolarizing shift in the voltage dependence of inactivation from -64.1±1.2mV (control), to -35.9±1.4mV, whereas it had no effect on the voltage dependence of activation. Furthermore, MC450 slowed current inactivation and the effect of MC450 was attenuated by the inactivation-impaired double mutant G628C/S631C.
Assuntos
Canal de Potássio ERG1/agonistas , Canal de Potássio ERG1/metabolismo , Mexiletina/análogos & derivados , Mexiletina/química , Ureia/análogos & derivados , Potenciais de Ação/efeitos dos fármacos , Avaliação Pré-Clínica de Medicamentos , Canal de Potássio ERG1/genética , Células HEK293 , Humanos , Mexiletina/metabolismo , Mexiletina/farmacologia , Mutagênese Sítio-Dirigida , Técnicas de Patch-Clamp , Estereoisomerismo , Ureia/química , Ureia/metabolismo , Ureia/farmacologiaRESUMO
Racemic mexiletine is a widely used antiarrhythmic agent that blocks sodium channels. The effects of R-(-) and S-(+) mexiletine stereoisomers on maximum rate of depolarization ([Formula: see text]), conduction time, and repolarization have not yet been investigated in isolated cardiac preparations. We studied the effect of the R-(-) and S-(+) mexiletine on rabbit cardiac action potential parameters by using the conventional microelectrode technique. Both enantiomers at 20 µmol/L of therapeutically and experimentally relevant concentration, significantly depressed the [Formula: see text] at fast heart rates (BCLs 300-700 ms). R-(-) mexiletine has more potent inhibitory effect than S-(+) mexiletine. Both R-(-) and S-(+) mexiletine significantly inhibited the [Formula: see text] of early extrasystoles measured at 70 ms diastolic interval induced by S1-S2 stimuli. R-(-) mexiletine has more pronounced inhibitory effect than S-(+) mexiletine. Both R-(-) and S-(+) mexiletine increased significantly the ERP/APD90 ratio. The time constant (τ) of recovery of [Formula: see text] was found to be τ = 376.0 ± 77.8 ms for R-(-) mexiletine and τ = 227.1 ± 23.4 ms for S-(+) mexiletine, which indicates a slower offset kinetics for R-(-) mexiletine from sodium channels than that of the S-(+) enantiomer. These data suggest that R-(-) mexiletine might be a more potent antiarrhythmic agent than S-(+) mexiletine.
Assuntos
Fenômenos Eletrofisiológicos/efeitos dos fármacos , Coração/efeitos dos fármacos , Coração/fisiologia , Mexiletina/química , Mexiletina/farmacologia , Rotação , Animais , Masculino , Potenciais da Membrana/efeitos dos fármacos , Coelhos , EstereoisomerismoRESUMO
Four mexiletine analogues have been tested for their antiarrhythmic, inotropic, and chronotropic effects on isolated guinea pig heart tissues and to assess calcium antagonist activity, in comparison with the parent compound mexiletine. All analogues showed from moderate to high antiarrhythmic activity. In particular, three of them (1b,c,e) were more active and potent than the reference drug, while exhibiting only modest or no negative inotropic and chronotropic effects and vasorelaxant activity, thus showing high selectivity of action. All compounds showed no cytotoxicity and 1b,c,d did not impair motor coordination. All in, these new analogues exhibit an interesting cardiovascular profile and deserve further investigation.
Assuntos
Antiarrítmicos/farmacologia , Antiarrítmicos/toxicidade , Mexiletina/farmacologia , Mexiletina/toxicidade , Animais , Antiarrítmicos/síntese química , Antiarrítmicos/química , Aorta/efeitos dos fármacos , Aorta/fisiopatologia , Sobrevivência Celular/efeitos dos fármacos , Técnicas de Química Sintética , Cães , Cobaias , Átrios do Coração/efeitos dos fármacos , Átrios do Coração/fisiopatologia , Células Hep G2 , Humanos , Células Madin Darby de Rim Canino , Mexiletina/síntese química , Mexiletina/química , Relaxamento Muscular/efeitos dos fármacosRESUMO
Mexiletine is an oral class IB antiarrhythmic agent. Although it was primarily studied for the treatment of ventricular arrhythmias, it has been demonstrated to be useful also for the treatment of chronic painful diabetic neuropathy, neuropathic pain, skeletal muscle channelopathies, and recently amyotrophic lateral sclerosis. This review presents a detailed report on the different synthetic routes to racemic and homochiral mexiletine developed in the last decades, as well as analytical studies regarding enantioseparation methods and enantiomeric excess determination. Finally, some analogues of mexiletine reported in the literature, most of which along with pharmacological studies, have been mentioned.
Assuntos
Antiarrítmicos/síntese química , Mexiletina/química , Antiarrítmicos/sangue , Antiarrítmicos/metabolismo , Antiarrítmicos/uso terapêutico , Arritmias Cardíacas/tratamento farmacológico , Cromatografia Líquida de Alta Pressão , Nefropatias Diabéticas/tratamento farmacológico , Humanos , Mexiletina/sangue , Mexiletina/metabolismo , Mexiletina/uso terapêutico , EstereoisomerismoRESUMO
The mechanism of cytochrome P450(CYP)-catalyzed hydroxylation of primary amines is currently unclear and is relevant to drug metabolism; previous small model calculations have suggested two possible mechanisms: direct N-oxidation and H-abstraction/rebound. We have modeled the N-hydroxylation of (R)-mexiletine in CYP1A2 with hybrid quantum mechanics/molecular mechanics (QM/MM) methods, providing a more detailed and realistic model. Multiple reaction barriers have been calculated at the QM(B3LYP-D)/MM(CHARMM27) level for the direct N-oxidation and H-abstraction/rebound mechanisms. Our calculated barriers indicate that the direct N-oxidation mechanism is preferred and proceeds via the doublet spin state of Compound I. Molecular dynamics simulations indicate that the presence of an ordered water molecule in the active site assists in the binding of mexiletine in the active site, but this is not a prerequisite for reaction via either mechanism. Several active site residues play a role in the binding of mexiletine in the active site, including Thr124 and Phe226. This work reveals key details of the N-hydroxylation of mexiletine and further demonstrates that mechanistic studies using QM/MM methods are useful for understanding drug metabolism.
Assuntos
Citocromo P-450 CYP1A2/metabolismo , Mexiletina/química , Mexiletina/metabolismo , Simulação de Dinâmica Molecular , Teoria Quântica , Citocromo P-450 CYP1A2/química , Humanos , Hidroxilação , Estrutura MolecularRESUMO
A novel class of NaV1.7 inhibitors has been identified by high-throughput screening followed by structure activity relationship studies. Among this series of compounds, piperidine 9o showed potent human and mouse NaV1.7 inhibitory activities with fair subtype selectivity over NaV1.5. Compound 9o successfully demonstrated analgesic efficacy in mice comparable to that of the currently used drug, mexiletine, but with an expanded central nervous system safety margin.
Assuntos
Descoberta de Drogas , Canal de Sódio Disparado por Voltagem NAV1.7/efeitos dos fármacos , Piperidinas/síntese química , Piperidinas/farmacologia , Bloqueadores do Canal de Sódio Disparado por Voltagem/síntese química , Bloqueadores do Canal de Sódio Disparado por Voltagem/farmacologia , Animais , Humanos , Concentração Inibidora 50 , Mexiletina/química , Mexiletina/farmacologia , Camundongos , Estrutura Molecular , Piperidinas/química , Bloqueadores do Canal de Sódio Disparado por Voltagem/químicaRESUMO
Semi-rational directed evolution was applied to the D5 variant of monoamine oxidase from Aspergillus niger (MAO-N-D5) with the aim of deriving the more desirable (R)-mexiletine through the kinetic resolution of mexiletine enantiomers. Although MAO-N-D5 shows no activity towards rac-mexiletine, theoretical molecular docking studies revealed the potential binding conformations of both mexiletine enantiomers and MAO-N-D5. The key factors affecting the catalytic activity and specificity were identified. Based on the docking results, six residues in the binding pocket and along the binding pathway were selected as key sites for saturation mutagenesis of MAO-N-D5. Through several rounds of screening and combinatorial experiments, two active MAO variants with high enantioselectivities towards (S)-mexiletine evolved, namely A-1 (F210V/L213C, E = 101) and AC-1 (F210V/I367T, E = 69). Molecular simulation experiments indicated that the introduced activity of these variants may be due to the reduced steric hindrance in the binding pocket of the relatively small-sized amino acid residues, a synergetic effect of the entrance residue mutation, and the formation of a new disulfide bond.
Assuntos
Evolução Molecular Direcionada/métodos , Mexiletina/metabolismo , Monoaminoxidase/metabolismo , Aspergillus niger/enzimologia , Interações Hidrofóbicas e Hidrofílicas , Cinética , Mexiletina/química , Simulação de Dinâmica Molecular , Monoaminoxidase/química , Mutagênese Sítio-Dirigida , Mutação , Ligação Proteica , Conformação Proteica , EstereoisomerismoRESUMO
Mexiletine belongs to class IB antiarrhythmic drugs and it is still considered a drug of choice for treating myotonias. However some patients do not respond to mexiletine or have significant side effects limiting its use; thus, alternatives to this drug should be envisaged. Mexiletine is extensive metabolized in humans via phase I and phase II reactions. Only a small fraction (about 10%) of the dose of mexiletine administered is recovered without modifications in urine. Although in the past decades Mex metabolites were reported to be devoid of biological activity, recent studies seem to deny this assertion. Actually, several hydroxylated metabolites showed pharmacological activity similar to that of Mex, thus contributing to its clinical profile. Purpose of this review is to summarize all the studies proposed till now about mexiletine metabolites, regarding structureactivity relationship studies as well as synthetic strategies. Biological and analytical studies will be also reported.
Assuntos
Mexiletina/metabolismo , Animais , Humanos , Mexiletina/administração & dosagem , Mexiletina/química , Estrutura MolecularRESUMO
Five d-amino acids have been used for the first time to synthesize chiral derivatizing reagents (as variants of Marfey's reagent) by nucleophilic displacement of one of the fluorine atoms in 1,5-difluoro-2,4-dinitrobenzene as against the literature reports on application of only l-amino acids or their amides as chiral auxiliaries in dinitrobenzene (DNB) moiety. Five other DNB based reagents were also prepared by nucleophilic substitution of fluorine atom with the set of the same amino acids in l-configuration, as chiral auxiliaries. These reagents were characterized and used for synthesis of diastereomers of (RS)-Mexiletine spiked in human plasma. Diastereomers were synthesized employing microwave irradiation and were separated on reversed-phase C18 column. Performance of the two types of chiral derivatizing reagents was compared. The reagents containing d-amino acids provided enhanced separation of diastereomers than those containing l-amino acids. The best resolution was obtained using mobile phase consisting of acetonitrile and 0.1% trifluoroacetic acid in gradient mode. The detection was carried out at 340nm. The method so developed was validated for linearity, accuracy and precision. The limit of quantitation was found to be approximately 25.2ngmL(-1) in human plasma.
Assuntos
Alanina/análogos & derivados , Aminoácidos/química , Análise Química do Sangue/métodos , Cromatografia Líquida , Mexiletina/química , Alanina/biossíntese , Amidas/química , Dinitrobenzenos , Humanos , Indicadores e Reagentes , Micro-Ondas , Sensibilidade e Especificidade , EstereoisomerismoRESUMO
Enantiomeric separation of racemic mexiletine and fluoxetine was achieved using three chiral derivatizing reagents (CDRs) based on (S)-naproxen. Diastereomers were synthesized by reaction of mexiletine or fluoxetine with the CDRs and were separated on a C18 column under reversed-phase conditions using a binary mixture of acetonitrile and triethylammonium phosphate/water, with UV detection at 230 and 226 nm. The results obtained for enantioseparation of the two drugs using the three CDRs were compiled and compared. The conditions for derivatization and chromatographic separation were optimized. The method was validated for linearity, repeatability, limit of detection and limit of quantification.
Assuntos
Cromatografia Líquida de Alta Pressão/métodos , Fluoxetina/química , Mexiletina/química , Naproxeno/química , Antiarrítmicos , Cromatografia Líquida de Alta Pressão/instrumentação , Fluoxetina/isolamento & purificação , Mexiletina/isolamento & purificação , Estrutura Molecular , EstereoisomerismoRESUMO
Mexiletine, an effective class IB antiarrhythmic agent, and its analogs were resolved on three different crown ether-based chiral stationary phases (CSPs), one (CSP 1) of which is based on (+)-(18-crown-6)-2,3,11,12-tetracarboxylic acid and the other two (CSP 2 and CSP 3) are based on (3,3'-diphenyl-1,1'-binaphthyl)-20-crown-6. Mexiletine was resolved with a resolution (R(S)) of greater than 1.00 on CSP 1 and CSP 3 containing residual silanol group-protecting n-octyl groups on the silica surface, but with a resolution (R(S)) of less than 1.00 on CSP 2. The chromatographic behaviors for the resolution of mexiletine analogs containing a substituted phenyl group at the chiral center on the three CSPs were quite dependent on the phenoxy group of analytes. Namely, mexiletine analogs containing 2,6-dimethylphenoxy, 3,4-dimethylphenoxy, 3-methylphenoxy, 4-methylphenoxy, and a simple phenoxy group were resolved very well on the three CSPs even though the chiral recognition efficiencies vary with the CSPs. However, mexiletine analogs containing 2-methylphenoxy group were not resolved at all or only slightly resolved. Among the three CSPs, CSP 3 was found to show the highest chiral recognition efficiencies for the resolution of mexiletine and its analogs, especially in terms of resolution (R(S)).
Assuntos
Cromatografia Líquida de Alta Pressão/métodos , Éteres de Coroa/química , Mexiletina/química , Mexiletina/isolamento & purificação , Mexiletina/análogos & derivados , EstereoisomerismoRESUMO
This study evaluates the influence of streptozotocin-induced diabetes on the kinetic disposition and metabolism of mexiletine (MEX) enantiomers in rats. Animals in the control (n = 6 for each blood collection time), diabetic (single intravenous dosage of 45 mg·(kg body mass)(-1) of streptozotocin), and insulin-treated groups (diabetic rats treated daily with 2 IU insulin) received by gavage a single dose of 10 mg·(kg body mass)(-1) racemic MEX. MEX enantiomers and the metabolites hydroxymethylmexiletine (HMM) and p-hydroxymexiletine PHM) were analyzed by LC-MS/MS. Statistical analysis was based on a serial sacrifice design, and parameter estimation was performed using a Bayesian modeling procedure. Area under the curve (AUC) for the (-)-(R) enantiomers of MEX, HMM, and PHM did not differ between the control and diabetic groups. However, AUC for (+)-(S)-MEX and (+)-(S)-HMM were lower in the diabetic than in the control group. Insulin treatment recovered glucose levels to normal and the (+)-(S)-MEX AUC and (+)-(S)-HMM AUC became similar to the AUCs observed in the nondiabetic animals.
Assuntos
Diabetes Mellitus Experimental/metabolismo , Mexiletina/farmacocinética , Animais , Área Sob a Curva , Insulina/sangue , Masculino , Mexiletina/química , Ratos Wistar , EstereoisomerismoRESUMO
Mexiletine is a very well-known class IB antiarrhythmic drug, whose enantiomers differ in both pharmacodynamic and pharmacokinetic properties, the (R)-isomer being the eutomer on experimental arrhythmias and in binding studies on cardiac voltage-gated sodium channels. meta-Hydroxymexiletine (MHM) is a minor metabolite of mexiletine, which has demonstrated to be more potent than the parent compound. Herein we report the synthesis and biological evaluation of MHM enantiomers for their potential antiarrhythmic activity. The same stereoselectivity pattern observed for mexiletine was found for MHM: the (R)-enantiomer of MHM was the eutomer on ac-arrhythmia also showing a negative inotropism higher than the one displayed by mexiletine and, at the same time, a decreased vasorelaxant activity on guinea-pig left atrium and guinea-pig ileum longitudinal smooth muscle.
Assuntos
Antiarrítmicos/farmacologia , Fibrilação Atrial/tratamento farmacológico , Átrios do Coração/efeitos dos fármacos , Mexiletina/análogos & derivados , Músculo Liso/efeitos dos fármacos , Animais , Antiarrítmicos/síntese química , Antiarrítmicos/química , Feminino , Cobaias , Átrios do Coração/metabolismo , Átrios do Coração/patologia , Mexiletina/síntese química , Mexiletina/química , Mexiletina/farmacologia , Estrutura Molecular , Músculo Liso/metabolismo , Músculo Liso/patologia , EstereoisomerismoRESUMO
Previously identified potent and/or use-dependent mexiletine (Mex) analogs were used as template for the rational design of new Na(v)-channel blockers. The effects of the novel analogs were tested on sodium currents of native myofibers. Data and molecular modeling show that increasing basicity and optimal alkyl chain length enhance use-dependent block. This was demonstrated by replacing the amino group with a more basic guanidine one while maintaining a proper distance between positive charge and aromatic ring (Me13) or with homologs having the chirality center nearby the amino group or the aromatic ring. Accordingly, a phenyl group on the asymmetric center in the homologated alkyl chain (Me12), leads to a further increase of use-dependent behavior versus the phenyl Mex derivative Me4. A fluorine atom in paraposition and one ortho-methyl group on the xylyloxy ring (Me15) increase potency and stereoselectivity versus Me4. Charge delocalization and greater flexibility of Me15 may increase its affinity for Tyr residues influencing steric drug interaction with the primary Phe residue of the binding site. Me12 and Me15 show limited selectivity against Na(v)-isoforms, possibly due to the highly conserved binding site on Na(v). To our knowledge, the new compounds are the most potent Mex-like Na(v) blockers obtained to date and deserve further investigation.
Assuntos
Mexiletina/farmacologia , Canal de Sódio Disparado por Voltagem NAV1.4/metabolismo , Bloqueadores dos Canais de Sódio/farmacologia , Células HEK293 , Humanos , Ativação do Canal Iônico/efeitos dos fármacos , Mexiletina/análogos & derivados , Mexiletina/química , Modelos Moleculares , Conformação Molecular , Músculos/efeitos dos fármacos , Músculos/metabolismo , Miocárdio/metabolismo , Especificidade de Órgãos/efeitos dos fármacos , Bloqueadores dos Canais de Sódio/química , EstereoisomerismoRESUMO
m-Hydroxymexiletine (MHM) is a metabolite of mexiletine, a well known class IB anti-arrhythmic drug, which presents almost twice the activity of the parent compound on cardiac voltage-gated sodium channels. Given the different activity of mexiletine enantiomers on sodium currents (being the R-isomer the eutomer), it is conceivable that (R)- and(S)-MHM could differ in pharmacodynamic and pharmacokinetic properties, too. Herein we report the efficient synthesis of MHM enantiomers that could represent useful tools for further investigations on stereospecific requirements of the voltage-gated sodium channel binding site. MHM enantiomers and all the homochiral intermediates were fully characterized. The ee values for (R)- and (S)-MHM were >99%, as assessed by capillary electrophoresis using ß-cyclodextrin sulfated sodium salt as a chiral selector.
Assuntos
Eletroforese Capilar/métodos , Mexiletina/análogos & derivados , Bloqueadores do Canal de Sódio Disparado por Voltagem/síntese química , Mexiletina/síntese química , Mexiletina/química , Estereoisomerismo , Sulfatos/química , Bloqueadores do Canal de Sódio Disparado por Voltagem/química , beta-Ciclodextrinas/químicaRESUMO
OBJECTIVES: This study examined the interaction of mexiletine enantiomers with human plasma, human serum albumin (HSA), and human α1-acid glycoprotein (hAGP), and characterized the binding modes of mexiletine enantiomers with hAGP in the molecular level. METHODS: Enantiomer separation of mexiletine was performed using precolumn derivatization chiral HPLC. The ultrafiltration technique was used to separate the free mexiletine in plasma matrix. Molecular dynamics simulations and free energy calculations were assessed using molecular mechanics and the generalized Born surface area method. KEY FINDINGS: Significant differences in enantioselective binding to human plasma were observed (R>S). The hAGP-mexiletine binding profile exhibited similar enantioselectivity (R>S) to that in human plasma, whereas HSA-mexiletine interaction was S>R at pH 7.4. Moreover, the results of comparative studies indicated that mexiletine had the highest binding affinity for F1-S, a variant of hAGP. Based on the computational studies, residues such as Arg90, Leu79, Ser89 and Phe89 showed an energy difference of more than -0.35 kcal/mol between the enantiomers. CONCLUSIONS: hAGP may be one of the key proteins leading to the enantioselective protein bindings of mexiletine in human plasma (R>S). The residues Arg90, Leu79, Ser89 and Phe89 of hAGP may have important roles in the observed enantioselectivity.