Lubeluzole, a neuroprotective anti-ischemic drug, and its enantiomer were prepared following a convenient procedure based on hydrolytic kinetic resolution. The ee values were >99% and 96%, respectively, as assessed by HPLC analysis. The chemosensitizing effects of both enantiomers were evaluated in combination with either doxorubicin (human ovarian adenocarcinoma A2780 cells) or paclitaxel (human lung carcinoma A549 cells) by the MTT assay. At the lowest concentrations used, lubeluzole showed an overall and remarkable tendency to synergize with both anticancer drugs. In ovarian cancer cells a clear prevalence of antagonistic effect was observed for the R-enantiomer. The synergistic effects of lubeluzole for both drugs were observed over a wide concentration window (0.005–5 lM), the lowest limit being at least 40 times lower than human plasma concentrations previously reported as causing serious side effects.

m-Hydroxymexiletine (MHM), a minor metabolite of the class IB anti-arrhythmic drug mexiletine, is about two fold more potent than the parent compound on human cardiac voltage-gated sodium channels (hNav1.5), and equipotent to mexiletine on human skeletal-muscle voltage-gated sodium channels (hNav1.4). Herein, an alternative and simplified synthesis of this promising compound has been accomplished. This route, as well as being more efficient, has the advantage, over the first, to avoid the use of oxidizing agents, such as the meta-chloroperoxybenzoic acid.

The simultaneous separation and quantification of the analytes within the minimum analysis time and the maximum resolution and efficiency are the main objectives in the development of a capillary electrophoretic method for the determination of solutes. In this paper we describe a specific, sensitive and robust method, using capillary zone electrophoresis with internal standard and UV detection, for the separation and quantification of the anti-arrhythmic drug mexiletine, its main phase I metabolites, and its main nitrogenous degradation product.

A series of chiral 2,3-dichlorophenoxy and 1-naphthyloxy alkylamines were synthesized, and their binding affinities towards 5-HT1D and h5-HT1B receptors were evaluated. In the naphthyloxy series, the (R)-prolinol derivative was the most selective 5-HT1D ligand, while (S)-N-methyl-2-(1-naphthyloxy)propan-1-amine showed the highest selectivity for h5-HT1B. Both compounds performed as 5-HT1D agonists in the isolated guinea pig assay and showed higher analgesic activity than both sumatriptan and the achiral analogue 20b in the mouse hotplate test. Neither ligand displayed any affinity for nicotinic ACh receptors present in mouse brain membranes, thus indicating that their analgesic activity does not arise through interaction with these receptors.

Previously identified potent and/or use-dependent mexiletine (Mex) analogs were used as template for the rational design of new Nav-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 Nav-isoforms, possibly due to the highly conserved binding site on Nav. To our knowledge, the new compounds are the most potent Mex-like Nav blockers obtained to date and deserve further investigation.

A series of phenoxyalkyl and phenylthioalkyl amides were prepared as melatoninergic ligands. Modulation of affinity of the newly synthesized compound by applying SARs around the terminal amide moiety, the alkyl chain, and the methoxy group on the aromatic ring provides compounds with nanomolar affinity for both melatonin receptor subtypes. Affinity towards MT1 and MT2 receptors were modulated also exploiting chirality. The investigation of intrinsic activity revealed that all the tested compounds behave as full or partial agonists.

Facile, alternative synthetic routes to (RS)-, (R)-, and (S)-3-benzyl-N-(2,6-dimethylphenyl)-1,3-oxazolidine-4-carboxamides (6), a chiral oxazolidine derivative of tocainide, are reported. The synthetic routes described herein also afforded (RS)-, (R)-, and (S)-11, which present the imidazolidin-4-one core and belong to a class of compounds interesting for their biological activities. All the final compounds and intermediates were fully characterized. Enantiomeric excesses of homochiral 6 and 11 were determined by capillary electrophoresis analysis using 2-hydroxypropyl-beta-cyclodextrin or highly sulfated gamma-cyclodextrin as chiral selectors.

A simple, convergent synthesis of the N-carbonyloxy β-d-glucuronide of mexiletine (sodium salt) in moderate yield is described. The compound is now available as an authentic reference standard for analytical studies, enabling more detailed investigation on the metabolism of mexiletine.

An efficient microwave-assisted synthesis of(±)-mandelic acid-5 was developed. e racemic mixture was resolved by diastereomeric salt formation using 1-phenylethylamine enantiomers as resolving agents. At each step, the resolution process was checked by determining mandelic acid-5 enantiomer ee values directly on fractional crystallized diastereomeric salts by chiral capillary electrophoresis analysis. Highly enriched (−)- and (+)-mandelic acid-5 (95% and 90% ee, resp.) were obtained and their absolute congurations— and , respectively—were determined by correlation of the (−)-mandelic acid-5 circular dichroism spectrum to the (R)-mande

Convenient synthetic routes to KN-93, N-(2-{[[(2E)-3-(4-chlorophenyl)prop-2-enyl](methyl)amino]methyl}phenyl)-N-(2-hydroxyethyl)-4-methoxybenzenesulfonamide, a well-known Ca(2+)/calmoduline-dependent protein kinase II (CaMKII) inhibitor, are described. The methods proposed start from easily available reagents and allow ready preparation of the final compound in moderate overall yields. Most of the synthetic steps proposed were microwave assisted.

Background and purpose: Pilsicainide, an anti-arrhythmic drug used in Japan, is described as a pure sodium channel blocker. We examined the mechanisms by which it is able to block open channels, because these properties may be especially useful to reduce hyperexcitability in pathologies characterized by abnormal sodium channel opening. Experimental approach: The effects of pilsicainide on various heterologously expressed human sodium channel subtypes and mutants were investigated using the patch clamp technique. Key results: Pilsicainide exhibited tonic and use-dependent effects comparable to those of mexiletine and flecainide on hNav1.4 channels. These use-dependent effects were abolished in the mutations F1586C and Y1593C within segment 6 of domain IV, suggesting that the interaction of pilsicainide with these residues is critical for its local anaesthetic action. Its affinity constants for closed channels (KR) and channels inactivated from the closed state (KI) were high, suggesting that its use-dependent block (UDB) requires the channel to be open for it to reach a high-affinity blocking site. Accordingly, basic pH, which slightly increased the proportion of neutral drug, dramatically decreased KR and KI values. Effects of pilsicainide were similar on skeletal muscle hNav1.4, brain hNav1.1 and heart hNav1.5 channels. The myotonic R1448C and G1306E hNav1.4 mutants were more and less sensitive to pilsicainide, respectively, due to mutation-induced gating modifications. Conclusions and implications: Although therapeutic concentrations of pilsicainide may have little effect on resting and closed-state inactivated channels, it induces a strong UDB due to channel opening, rendering the drug ideally suited for inhibition of high-frequency action potential firing.

Lubeluzole, which acts on various targets in vitro, including voltage-gated sodium channels, was initially proposed as a neuroprotectant. The lubeluzole structure contains a benzothiazole moiety [N-methyl-1,3-benzothiazole-2-amine (R-like)] related to riluzole and a phenoxy-propranol-amine moiety [(RS)-1-(3,4-difluorophenoxy)-3-(piperidin-1-yl)propan-2-ol (A-core)] recalling propranolol. Both riluzole and propranolol are efficient sodium channel blockers. We studied in detail the effects of lubeluzole (racemic mixture and single isomers), the aforementioned lubeluzole moieties, and riluzole on sodium channels to increase our knowledge of drug-channel molecular interactions. Compounds were tested on hNav1.4 sodium channels, and on F1586C or Y1593C mutants functionally expressed in human embryonic kidney 293 cells, using the patch-clamp technique. Lubeluzole blocked sodium channels with a remarkable effectiveness. No stereoselectivity was found. Compared with mexiletine, the dissociation constant for inactivated channels was ∼600 times lower (∼11 nM), conferring to lubeluzole a huge use-dependence of great therapeutic value. The F1586C mutation only partially impaired the use-dependent block, suggesting that additional amino acids are critically involved in high-affinity binding. Lubeluzole moieties were modest sodium channel blockers. Riluzole blocked sodium channels efficiently but lacked use dependence, similar to R-like. F1586C fully abolished A-core use dependence, suggesting that A-core binds to the local anesthetic receptor. Thus, lubeluzole likely binds to the local anesthetic receptor through its phenoxy-propranol-amine moiety, with consequent use-dependent behavior. Nevertheless, compared with other known sodium channel blockers, lubeluzole adds a third pharmacophoric point through its benzothiazole moiety, which greatly enhances high-affinity binding and use-dependent block. If sufficient isoform specificity can be attained, the huge use-dependent block may help in the development of new sodium channel inhibitors to provide pharmacotherapy for membrane excitability disorders, such as myotonia, epilepsy, or chronic pain.

We previously showed that the β-adrenoceptor modulators, clenbuterol and propranolol, directly blocked voltage-gated sodium channels, whereas salbutamol and natolo did not (Desaphy et al., 2003), suggesting the presence of two hydroxyl groups on the aromatic moiety of the drugs as a molecular requisite for impeding sodium channel block. To verify such an hypothesis, we synthesized five new mexiletine analogs by adding one or two hydroxyl groups to the aryloxy moiety of the sodium channel blocker and tested these compounds on hNav1.4 channels expressed in HEK293 cells. Concentration–response relationships were constructed using 25-mslong depolarizing pulses at −30mV applied from an holding potential of −120mV at 0.1Hz (tonic block) and 10 Hz (use-dependent block) stimulation frequencies. The half-maximum inhibitory concentrations (IC50) were linearly correlated to drug lipophilicity: the less lipophilic the drug, minor was the block. The same compounds were also tested on F1586C and Y1593C hNav1.4 channel mutants, to gain further information on the molecular interactions of mexiletine with its receptor within the sodium channel pore. In particular, replacement of Phe1586 and Tyr1593 bynon-aromatic cysteine residues may help in the understanding of the role of π–πorπ–cation interactions in mexiletine binding. Alteration of tonic block suggests that the aryloxy moiety of mexiletine may interact either directly or indirectly with Phe1586 in the closed sodium channel to produce low-affinity binding block, and that this interaction depends on the electrostatic potential of the drug aromatic tail. Alteration of use-dependent block suggests that addition of hydroxyl groups to the aryloxy moiety may modify high-affinity binding of the drug amine terminal to Phe1586 through cooperativity between the two pharmacophores, this effect being mainly related to drug lipophilicity. Mutation of Tyr1593 further impaired such cooperativity. In conclusion, these results confirm our former hypothesis by showing that the presence of hydroxyl groups to the aryloxy moiety of mexiletine greatly reduced sodium channel block, and provide molecular insights into the intimate interaction of local anesthetics with their receptor.

Recently a series of chiral N-(phenoxyalkyl)amides have been reported as potent MT1 and MT2 melatonergic ligands. Some of these compounds were selected and tested for their antioxidant properties by measuring their reducing effect against oxidation of 20,70-dichlorodihydrofluorescein (DCFH) in the DCFHdiacetate (DCFH-DA) assay. Among the tested compounds, N-[2-(3-methoxyphenoxy)propyl]butanamide displayed potent antioxidant activity that was stereoselective, the (R)-enantiomer performing as the eutomer. This compound displayed strong cytoprotective activity against H2O2-induced cytotoxicity resulting slightly more active than melatonin, and performed as Ca2+/calmodulin-dependent kinase II (CaMKII) inhibitor, too.

Several members of a new family of non-sugar-type α-glucosidase inhibitors, bearing a phthalimide moiety connected to a variously substituted phenoxy ring by an alkyl chain, were synthesized and their activities were investigated. The efficacy of the inhibition activity appeared to be governed by the chain length of the substrate. Substrates possessing 10 carbons afforded the highest levels of activity, which were one to two orders of magnitude more potent than the known inhibitor 1-deoxynojirimycin (dNM). Furthermore, structure-activity relationship studies indicated a critical role of electron-withdrawing substituents at the phenoxy group for the activity. Derivatives bearing a chlorine atom along with a strong electron-withdrawing group, such as a nitro group, were the most potent of the series.

The antioxidant, anti-a-glucosidase and anticholinesterase activity of the leaves and rhizomatous extract of Bergenia cordifolia were investigated. The rhizomes extract that showed a higher degree of 1,1-diphenyl-2- picrylhydrazyl radical scavenging and anti-a-glucosidase activity than reference compounds (rutin and acarbose respectively) were subjected to phytochemical analysis. The study revealed that previously unknown minor constituents from the plant, (+)-catechin 3-O-gallate, (+)-catechin 3,5-di-O-gallate and 1,2,4,6-tetra-O-galloylb- D-glucopyranoside, were the radical scavenging and anti-a-glucosidase principles. These compounds as well as the crude extracts were weak acetylcholienesterase inhibitors, suggesting a higher degree of selectivity against a-glucosidase enzyme. In comparison with the minor constituents, the previously known major constituents of the plant, bergenin and arbutin, were poor radical scavengers and enzyme inhibitors. Copyright © 2011 John Wiley & Sons, Ltd.

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.

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 β-cyclodextrin sulfated sodium salt as a chiral selector.

Inhibition of drug efflux pumps such as P-glycoprotein (P-gp) is an approach toward combating multidrug resistance, which is a significant hurdle in current cancer treatments. To address this, N-substituted aryloxymethyl pyrrolidines were designed and synthesized in their homochiral forms in order to investigate the stereochemical requirements for the binding site of Pgp. Our study provides evidence that the chiral property of molecules could be a strategy for improving the capacity for interacting with P-gp, as the most active compounds of the series stereoselectively modulated this efflux pump. The naphthalene- 1-yl analogue (R)-2-[(2,3-dichlorophenoxy)methyl]-1- (naphthalen-1-ylmethyl)pyrrolidine) [(R)-7a] emerged foremost for its potency and stereoselectivity toward P-gp, with the S enantiomer being nearly inactive. The modulation of P-gp by (R)-7a involved consumption of ATP, thus demonstrating that the compound behaves as a P-gp substrate.

New chiral mexiletine analogs were synthesized in their optically active forms and evaluated in vitro as use-dependent blockers of skeletal muscle sodium channels. Tests carried out on sodium currents of single muscle fibers of Rana esculenta demonstrated that all of them exerted a higher use-dependent block than mexiletine. The most potent analog, (S)-3-(2,6-dimethylphenoxy)-1-phenylpropan-1-amine (S)-(5), was six-fold more potent than (R)-Mex in producing a tonic block. As observed with mexiletine, the newly synthesized compounds exhibit modest enantioselective behavior, that is more evident in 3-(2,6-dimethylphenoxy)butan-1-amine (3).

The first synthesis of m-hydroxymexiletine (MHM) has been accomplished. MHM displayed hNav1.5 sodium channel blocking activity, and tests indicate it to be ∼2-fold more potent than the parent mexiletine and to have more favorable toxicological properties than mexiletine. Thus, MHM and possible related prodrugs might be studied as agents for the treatment of arrhythmias, neuropathic pain, and myotonias in substitution of mexiletine (metabolite switch), which has turned out to be tainted with common toxicity.

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.