Ultrasound-assisted electromembrane extraction of clonazepam from plasma and determination using capillary electrophoresis.

In this work, ultrasound-assisted electromembrane extraction (UA-EME) coupled with capillary electrophoresis (CE) and diode array detection (DAD) was developed for the determination of clonazepam from plasma samples. A comparative study was carried out between conventional EME and UA-EME methods to investigate the influence of the ultrasound waves on the extraction efficiency. The central composite design was used for the optimization of the variables affecting these methods to achieve the best extraction efficiency. Under optimal extraction conditions, the UA-EME provided better extraction recovery in a shorter time (58% in 13 min) than the EME method (42% in 30 min). Ultrasound reduces the extraction time and increased recovery by reducing the thickness of the barrier layer. In addition, this method provided a higher pre-concentration factor (203) and a lower limit of detection (3 ng mL-1) with good repeatability (RSDs were less than 10.11%).

Estudio comparativo de la calidad biofarmacéutica de Clonazepam 0.5 mg comercializados en el mercado peruano / Comparative study of the biopharmaceutical quality of Clonazepam 0.5 mg commercialized in the Peruvian market

INTRODUCCIÓN: el Clonazepam pertenece a un grupo de medicamentos llamados benzodiazepinas. Se sabe que estos medicamentos actúan en el cerebro a través del GABA. Es un anticonvulsivante utilizado para varios tipos de ataques, incluyendo ataques miotónicos o atónicos, epilepsia fotosensible, y crisis de ausencia, aunque puede desarrollarse tolerancia. Raras veces es eficaz en ataques tónico-clónicos generalizados o parciales. MÉTODO: el presente estudio se realizó para analizar los parámetros comparativos de control de calidad in vitro mediante la evaluación de la variación de peso, friabilidad, dureza, tiempo de desintegración y perfil de disolución entre el medicamento innovador (Rivotril®) y medicamentos multifuente que son comercializados en el mercado peruano. Para realizar el estudio comparativo, se seleccionaron tabletas de Clonazepam 0,5 mg multifuente de diferentes laboratorios comparándolos con el medicamento innovador y se evaluaron las características fisicoquímicas y biofarmacéuticas. Los ensayos farmacopeicos se evaluaron según lo establecido en la USP 42. RESULTADOS: los resultados permitieron establecer que todas las marcas analizadas cumplieron los criterios de aceptación establecidos en la farmacopea para cada principio activo y que el comportamiento biofarmacéutico de ellas era muy similar para ambos tipos de molécula. CONCLUSIONES: se estableció que todas las tabletas multifuente de Clonazepam 0,5 mg incluidos en esta investigación son bioequivalentes con la marca innovadora elegida y, por lo que permite proponer a la comunidad científica la determinación de la equivalencia biofarmacéutica como elemento de apoyo en la toma de decisiones de compra en el servicio farmacéutico

INTRODUCTION: Clonazepam belongs to a group of medications called benzodiazepines. It is known that these drugs act in the brain through GABA. It is an anticonvulsant used for various types of attacks, including myotonic or atonic attacks, photosensitive epilepsy, and absence attacks, although tolerance may develop. It is rarely effective in generalized or partial tonic-clonic attacks. METHOD: the present study was carried out to analyze the comparative parameters of in vitro quality control by evaluating the variation in weight, friability, hardness, disintegration time and dissolution profile between the innovative drug (Rivotril®) and multi-source drugs that are marketed in the Peru¬vian market. To carry out the comparative study, Clonazepam 0.5 mg multi-source tablets were selected from different laboratories comparing them with the innovative medicine and the physicochemical and biopharmaceutical characteristics were evaluated. Pharmacopoeial trials were evaluated as established in USP 42. RESULTS: the results made it possible to establish that all the brands analyzed met the acceptance criteria established in the pharmacopoeia for each active ingredient and that their biopharmaceutical behavior was very similar for both types of molecule

Fragmentation studies of selected drugs utilized in palliative care.

The results of research on selected drugs used in palliative care are presented, including fentanyl, tramadol, metoclopramide, hyoscine butylbromide, midazolam, haloperidol, levomepromazine and clonazepam. Interpretation of their ESI mass spectra obtained by the use of a triple quadrupole linear ion trap mass spectrometer is given. As a result, fragmentation pathways described in the literature are complemented and presented with more details. On their basis, transitions for quantitative analysis are selected and chromatographic conditions for the determination of the palliative care drugs are proposed as well. These results enable future studies on palliative care drugs in elderly patients including both their quantitation in body fluids and easier identification of their metabolites.

Spectroscopic and molecular docking approaches for investigating conformation and binding characteristics of clonazepam with bovine serum albumin (BSA).

Clonazepam, a type of benzodiazepine, is a classical drug used to prevent and treat seizures, panic disorder, movement disorder, among others. For further clarifying the distribution of clonazepam in vivo and the pharmacodynamic and pharmacokinetic mechanisms, the binding interaction between clonazepam and bovine serum albumin (BSA) was investigated using ultraviolet spectroscopy (UV), steady-state fluorescence spectroscopy, synchronous fluorescence spectroscopy, three-dimensional (3D) fluorescence spectroscopy, Fourier transform infrared spectroscopy (FT-IR) and molecular docking methods. The results well confirmed that clonazepam bound on the subdomain III A (Site II) of BSA through van der Waals force and hydrogen bonding interaction, and quenched the intrinsic fluorescence of BSA through a static quenching process. The number of binding sites (n) and binding constant (Kb) of clonazepam-BSA complex were about 1 and 7.94×104M-1 at 308K, respectively. The binding process of clonazepam with BSA was spontaneous and enthalpy-driven process due to ΔG0<0 and|ΔH0|>T|ΔS0| over the studied temperature range. Meanwhile, the binding interaction of clonazepam with BSA resulted in the slight change in the conformation of BSA and the obvious change in the conformation of clonazepam, implying that the flexibility of clonazepam also played an important role in increasing the stability of the clonazepam-BSA complex.

Intranasal brain-targeted clonazepam polymeric micelles for immediate control of status epilepticus: in vitro optimization, ex vivo determination of cytotoxicity, in vivo biodistribution and pharmacodynamics studies.

Clonazepam (CZ) is an anti-epileptic drug used mainly in status epilepticus (SE). The drug belongs to Class II according to BCS classification with very limited solubility and high permeability and it suffers from extensive first-pass metabolism. The aim of the present study was to develop CZ-loaded polymeric micelles (PM) for direct brain delivery allowing immediate control of SE. PM were prepared via thin film hydration (TFH) technique adopting a central composite face-centered design (CCFD). The seventeen developed formulae were evaluated in terms of entrapment efficiency (EE), particle size (PS), polydispersity index (PDI), zeta potential (ZP), and in vitro release. For evaluating the in vivo behavior of the optimized formula, both biodistrbution using 99mTc-radiolabeled CZ and pharmacodynamics studies were done in addition to ex vivo cytotoxicty. At a drug:Pluronic® P123:Pluronic® L121 ratio of 1:20:20 (PM7), a high EE, ZP, Q8h, and a low PDI was achieved. The biodistribution studies revealed that the optimized formula had significantly higher drug targeting efficiency (DTE = 242.3%), drug targeting index (DTI = 144.25), and nose-to-brain direct transport percentage (DTP = 99.30%) and a significant prolongation of protection from seizures in comparison to the intranasally administered solution with minor histopathological changes. The declared results reveal the ability of the developed PM to be a strong potential candidate for the emergency treatment of SE.

Polymeric mucoadhesive tablets for topical or systemic buccal delivery of clonazepam: Effect of cyclodextrin complexation.

Two kinds of mucoadhesive buccal tablets of clonazepam (CLZ) were developed to provide, a prolonged local or systemic delivery respectively. Tablets prepared by direct compression of combinations of different polymers were tested for swelling, erosion and residence time properties. Carbopol 971P/hydroxypropylmethylcellulose and Poloxamer/chitosan mixtures were the best and were selected for drug loading. The effect of CLZ complexation with different cyclodextrins was investigated. Randomly-methylated-ßCD (RAMEßCD) was the most effective, allowing 100% drug released increase from local-delivery buccal tablets. Kollicoat was the best among the tested backing-layers, assuring a unidirectional release from systemic-delivery buccal tablets (<0.8% drug released in simulated saliva after 24h). In vitro permeation studies from coated-tablets showed that CLZ loading as RAMEßCD-coground enabled a 5-times increase in drug flux and permeability. Therefore, complexation with RAMEßCD was a successful strategy to improve the CLZ performance from buccal tablets for both local or systemic action.

Stability of Atenolol, Clonazepam, Dexamethasone, Diclofenac Sodium, Diltiazem, Enalapril Maleate, Ketoprofen, Lamotrigine, Penicillamine-D, and Thiamine in SyrSpend SF PH4 Oral Suspensions.

The objective of this study was to evaluate the stability of 10 commonly used active pharmaceutical ingredients compounded in oral suspensions using SyrSpend SF PH4 (atenolol 1.0 and 5.0 mg/mL, clonazepam 0.2 mg/mL, dexamethasone 1.0 mg/mL, diclofenac sodium 5.0 mg/mL, diltiazem 12.0 mg/mL, enalapril maleate 1.0 mg/mL, ketoprofen 20.0 mg/mL, lamotrigine 1.0 mg/mL, penicillamine-D 50.0 mg/mL, thiamine 100 mg/m) and stored both at controlled refrigerated (2°C to 8°C) and room temperature (20°C to 25°C). Stability was assessed by means of measuring percent recovery at varying time points throughout a 90-day period. The quantification of the active pharmaceutical ingredients was performed by a stability-indicating, high-performance liquid chromatographic method. The beyond-use date of the products was found to be at least 90 days for all suspensions (except atenolol 1 mg/mL, which was stable up to 60 days), both for controlled refrigerated temperature and room temperature. This confirms that SyrSpend SF PH4 is a stable suspending vehicle for compounding with a broad range of different active pharmaceutical ingredients.

Development and application of novel clonazepam molecularly imprinted coatings for stir bar sorptive extraction.

The molecularly imprinted magnetic stir bar coatings were created based on graft-functional Fe3O4 nanoparticles with magnetic field-induced self-assembly. The magnetic complex including clonazepam as template, the graft-functional Fe3O4 nanoparticles and methacrylic acid as monomers was pre-assembled through π-π interaction and hydrogen bonding, then was directionally adsorbed on the surface of magnetic stir bar under the magnetic induction. The molecularly imprinted coating with well-ordered structure was generated by one-step copolymerization based on the cross linking of ethylene glycol dimethacrylate. The molecularly imprinted coating with multiple recognition sites could be manufactured and applied in polar solvents, and showed superior selectivity and fast binding kinetics for benzodiazepines. The analytes in herbal health foods, treated by stir bar sorptive extraction, were determined by HPLC-UV. Good linearity was observed in the range of 0.01-2 µg mL(-1). The content of clonazepam in the herbal health foods was found to be 44 ng g(-1), and the average recoveries were 89.8-103.3% with a relative standard deviation (RSD) <6.5%, demonstrating the successful application in real sample analysis.

Development of an ultra-high-performance liquid chromatography coupled to high-resolution quadrupole-Orbitrap mass spectrometry method for the rapid detection and confirmation of illegal adulterated sedative-hypnotics in dietary supplements.

A novel method using ultra-high performance liquid chromatography coupled to hybrid quadrupole-Orbitrap high-resolution mass spectrometry (UHPLC-Q-Orbitrap) was developed and validated for the simultaneous screening, identification and quantification of sedative-hypnotics in dietary supplements. Chromatographic conditions were optimised and a full data-dependent MS(2) scan (MS/dd-MS(2)) in positive and negative ion mode was used. A single injection was sufficient to perform the simultaneous screening and identification/quantification of samples. The response showed a good linear relationship with analyte concentrations over wide ranges (e.g., 1.0-1000 ng g(-1) for diazepam) with all the determination coefficients (r(2)) > 0.9985. The method was validated, obtaining accuracy (intra- and inter-day) in the range of 94.5-105.3% and precision (intra- and inter-day) in the range of 0.4-8.9%, respectively. The detection limits (LODs) were in the range of 0.3-1.0 ng g(-1) for different analytes. Recoveries were performed and ranged from 74.1% to 90.2%, while all matrix effects were over the range of 85.4-93.6%. Finally, this method was used to detect sedative-hypnotics in commercial dietary supplements. Of a total of 45 batches of dietary supplements, only three batches were found to be positive samples with concentrations of diazepam, clonazepam and alprazolam at high levels (≥ 8.22 mg g(-1)).

Benzothiazepine CGP37157 and its 2'-isopropyl analogue modulate Ca²âº entry through CALHM1.

CALHM1 is a Ca(2+) channel discovered in 2008, which plays a key role in the neuronal electrical activity, among other functions. However, there are no known efficient blockers able to modulate its Ca(2+) handling ability. We herein describe that benzothiazepine CGP37157 and its newly synthesized analogue ITH12575 reduced Ca(2+) influx through CALHM1 at low micromolar concentrations. These results could serve as a starting point for the development of more selective CALHM1 ligands using CGP37157 as a hit compound, which would help to study the physiological role of CALHM1 in the control of [Ca(2+)]cyt in excitable cells, as well as its implication in CNS diseases.

Development of liposomal and microemulsion formulations for transdermal delivery of clonazepam: effect of randomly methylated ß-cyclodextrin.

Transdermal administration of clonazepam, a poorly water-soluble benzodiazepine, is an interesting strategy for overcoming the drawbacks of its oral administration. With this aim, two nano-carrier formulations, based on ultra-deformable liposomes and microemulsions, have been developed to favour clonazepam transdermal delivery. Considering the solubilizing power of methyl-ßcyclodextrin (Me-ßCD) toward clonazepam and its potential positive influence on transdermal drug delivery, the effect of its addition to these formulations was investigated. Artificial lipophilic membranes simulating the skin allowed a rapid evaluation of the drug permeation properties from the systems, compared with those from an aqueous drug suspension, with or without Me-ßCD. The best formulations were further characterized by permeation through excised rabbit ear skin. All the formulations increased drug permeability, ranging from 2-fold (liposomes without Me-ßCD), up to over 4-fold (microemulsions containing Me-ßCD). The different formulations allowed for pointing out different possible permeation enhancing mechanisms of Me-ßCD: increase in drug solubility and thermodynamic activity in the vehicle, when added to the drug aqueous suspension; interactions with the vesicle bilayer, in case of liposomal formulations; interactions with the skin membrane lipids, as evidenced in experiments with excised rabbit ear for microemulsions containing Me-ßCD, that were then selected for further in vivo studies.

Clobazam and its active metabolite N-desmethylclobazam display significantly greater affinities for α2- versus α1-GABA(A)-receptor complexes.

Clobazam (CLB), a 1,5-benzodiazepine (BZD), was FDA-approved in October 2011 for the adjunctive treatment of seizures associated with Lennox-Gastaut syndrome (LGS) in patients 2 years and older. BZDs exert various CNS effects through allosteric modulation of GABAA receptors. The structurally distinct, 1,4-BZD clonazepam (CLN) is also approved to treat LGS. The precise mechanisms of action and clinical efficacy of both are unknown. Data show that the GABAA α1-subunit-selective compound zolpidem [ZOL] exhibits hypnotic/sedative effects. Conversely, data from knock-in mice carrying BZD binding site mutations suggest that the α2 subunit mediates anticonvulsant effects, without sedative actions. Hence, the specific pattern of interactions across the GABAA receptor complexes of BZDs might be reflected in their clinical efficacies and adverse effect profiles. In this study, GABAA-receptor binding affinities of CLB, N-desmethylclobazam (N-CLB, the major metabolite of CLB), CLN, and ZOL were characterized with native receptors from rat-brain homogenates and on cloned receptors from HEK293 cells transfected with combinations of α (α1, α2, α3, or α5), ß2, and γ2 subtypes. Our results demonstrate that CLB and N-CLB have significantly greater binding affinities for α2- vs. α1-receptor complexes, a difference not observed for CLN, for which no distinction between α2 and α1 receptors was observed. Our experiments with ZOL confirmed the high preference for α1 receptors. These results provide potential clues to a new understanding of the pharmacologic modes of action of CLB and N-CLB.

Physico-chemical characterization in solution and in the solid state of clonazepam complexes with native and chemically-modified cyclodextrins.

Clonazepam (CLZ) is a benzodiazepine derivative, whose bioavailability, limited by its very poor water-solubility, could be improved by cyclodextrin complexation. However, the choice of the most proper cyclodextrin to use to fully exploit its potential favourable effects on the drug, is a critical step. Therefore, in the present work, the performance of some amorphous cyclodextrin (CD) derivatives in terms of complexing, solubilizing and amorphizing power towards CLZ was carefully evaluated and compared with that of natural CDs. The role of CD cavity size, amorphous or crystalline nature, and presence and type of substituents on its ability in producing effective interactions with the drug has been investigated. Equimolar CLZ-CD solid systems were obtained by blending, kneading, co-grinding and coevaporation. Drug-CD interactions were investigated by phase-solubility analysis, differential scanning calorimetry and X-ray powder diffractometry. Among the natural CDs, ß-CD showed the highest complexing ability, suggesting that its cavity size is the most proper to host the drug molecule. The presence of substituents had a negative effect on the performance of α-CD and γ-CD, while it improved the complexing and solubilizing power of ß-CD, and the methylated derivative was more effective than the hydroxypropylated one. Solid-state studies revealed that amorphous CDs had highest amorphizing power than the corresponding natural crystalline ones, and methylated-ß-CD (Me-ß-CD) was the best carrier. As for the preparation method, co-grinding was the most powerful in promoting the formation of efficacious drug-CD solid-state interactions. Dissolution rate studies confirmed Me-ß-CD as the best partner for CLZ and co-grinding as the best method for maximizing the drug dissolution properties. Therefore, co-ground products with Me-ß-CD could be selected as the best system for future development of CLZ formulations with improved therapeutic efficacy.

A new chemiluminescence method for determination of clonazepam and diazepam based on 1-Ethyl-3-Methylimidazolium Ethylsulfate/copper as catalyst.

A novel chemiluminescence (CL) reaction, Benzodiazepines-H2O2-1-Ethyl-3-Methylimidazolium Ethylsulfate/copper, for determination of clonazepam and diazepam at nanogram per milliliter level in batch-type system have been described. The method relies on the catalytic effect of 1-Ethyl-3-Methylimidazolium Ethylsulfate/copper on the chemiluminescence reaction of Benzodiazepines, the oxidation of Benzodiazepines with hydrogen peroxide in natural medium. The influences of various experimental parameters such as solution pH, the ratio of 1-Ethyl-3 Methylimidazolium ethylsulfate concentration to copper ion, the type of buffer and the concentration of CL reagents were investigated. Under the optimum condition, the proposed method was satisfactorily applied for the determination of these drugs in tablets and urine without the interference of their potential impurities.

Dependence of the kinetic and thermodynamic parameters on hydrophilic-lipophilic character of alprazolam, clonazepam, diazepam, doxepin and haloperidol in alkaline environment.

Examination of the stability of clonazepam, diazepam, alprazolam, haloperidol, and doxepin in basic solutions was performed, together with an assessment of the kinetic (k, t0.1i t0.5) and thermodynamic (Ea, ΔH(++)i ΔS(++)) stability-indicating parameters, which were compared with the lipophilicity (logP) of the studied drugs. It was observed that the calculated values of Ea, ΔH(++) and ΔS(++) for the studied drugs increased from 41.04 kJ/mol to 125.50 kJ/mol, from 37.82 kJ/mol to 122.24 kJ/mol and from -167.09 J/Kmol to 53.02 J/Kmol, respectively, along with an increase of lipophilicity (logP) from 2.12 to 4.30 for the most hydrophilic alprazolam to the most lipophilic haloperidol. The degradation products were identified using UPLC/MS/MS method.

Melamine modified gold nanoprobe for "on-spot" colorimetric recognition of clonazepam from biological specimens.

Inexpensive, rapid, and reliable methods of detection are crucial to the control of toxicological investigations. Here we report a highly sensitive, selective and cost effective method for the detection of trace amounts of clonazepam based on gold nanoparticles (AuNPs) in the presence of melamine. Hydrogen bonding interactions between clonazepam and melamine resulted in the aggregation of AuNPs and a consequent color change of AuNPs from wine red to blue. The results showed that the absorption ratio (A636/A552) was linear for clonazepam concentrations in the range of 10 × 10(-8) to 1.0 × 10(-9) M (R(2) = 0.999). The detection limit was 8.9 × 10(-10) M (S/N = 3), which was much lower than that of most existing methods. Coexisting substances including alprazolam, diazepam, nitrazepam and lorazepam did not affect the determination of clonazepam. The sensor developed by this new approach could be used as a spot test and a good alternative means for on-site and real time screening of clonazepam. This proposed scheme was also supported by the use of real samples such as skeletal remains and blood to illustrate the applicability of the developed nanosensor by a series of experiments.

Stability-indicating RP-HPLC method for the simultaneous determination of escitalopram oxalate and clonazepam.

The objective of the current study was to develop a validated, specific stability-indicating reversed-phase liquid chromatographic (LC) method for the quantitative determination of escitalopram oxalate and clonazepam and their related substances in bulk drugs and pharmaceutical dosage forms in the presence of degradation products. Forced degradation studies were performed on the pure drugs of escitalopram oxalate and clonazepam, as per the stress conditions prescribed by the International Conference on Harmonization (ICH) using acid, base, oxidation, thermal stress and photolytic degradation to show the stability-indicating power of the method. Significant degradation was observed during acid and alkaline hydrolysis and no degradation was observed in other stress conditions. The chromatographic method was optimized using the samples generated from forced degradation studies. Good resolution between the peaks corresponded to the active pharmaceutical ingredients, escitalopram oxalate and clonazepam, and degradation products from the analyte were achieved on an ODS Hypersil C18 column (250 × 4.6 mm) using a mobile phase consisting of a mixture of acetonitrile-50 mM phosphate buffer + 10 mM triethylamine (70:30, v/v). The detection was conducted at 268 nm. The limit of detection and the limit of quantitation for escitalopram oxalate and clonazepam were established. The stress test solutions were assayed against the qualified working standards of escitalopram oxalate and clonazepam, which indicated that the developed LC method was stability-indicating. Validation of the developed LC method was conducted as per ICH requirements. The developed LC method was found to be suitable to check the quality of bulk samples of escitalopram oxalate and clonazepam.

Benzothiazepine CGP37157 and its isosteric 2'-methyl analogue provide neuroprotection and block cell calcium entry.

Benzothiazepine CGP37157 is widely used as tool to explore the role of mitochondria in cell Ca(2+) handling, by its blocking effect of the mitochondria Na(+)/Ca(2+) exchanger. Recently, CGP37157 has shown to exhibit neuroprotective properties. In the trend to improve its neuroprotection profile, we have synthesized ITH12505, an isosteric analogue having a methyl instead of chlorine at C2' of the phenyl ring. ITH12505 has exerted neuroprotective properties similar to CGP37157 in chromaffin cells and hippocampal slices stressed with veratridine. Also, both compounds afforded neuroprotection in hippocampal slices stressed with glutamate. However, while ITH12505 elicited protection in SH-SY5Y cells stressed with oligomycin A/rotenone, CGP37157 was ineffective. In hippocampal slices subjected to oxygen/glucose deprivation plus reoxygenation, ITH12505 offered protection at 3-30 µM, while CGP37157 only protected at 30 µM. Both compounds caused blockade of Ca(2+) channels in high K(+)-depolarized SH-SY5Y cells. An in vitro experiment for assaying central nervous system penetration (PAMPA-BBB; parallel artificial membrane permeability assay for blood-brain barrier) revealed that both compounds could cross the blood-brain barrier, thus reaching their biological targets in the central nervous system. In conclusion, by causing a mild isosteric replacement in the benzothiazepine CGP37157, we have obtained ITH12505, with improved neuroprotective properties. These findings may inspire the design and synthesis of new benzothiazepines targeting mitochondrial Na(+)/Ca(2+) exchanger and L-type voltage-dependent Ca(2+) channels, having antioxidant properties.

Synthesis, biological evaluation, and structure-activity relationship of clonazepam, meclonazepam, and 1,4-benzodiazepine compounds with schistosomicidal activity.

The inherent morbidity and mortality caused by schistosomiasis is a serious public health problem in developing countries. Praziquantel is the only drug in therapeutic use, leading to a permanent risk of parasite resistance. In search for new schistosomicidal drugs, meclonazepam, the 3-methyl-derivative of clonazepam, is still considered an interesting lead-candidate because it has a proven schistosomicidal effect in humans but adverse effects on the central nervous system did not allow its clinical use. Herein, the synthesis, in vitro biological evaluation, and molecular modeling of clonazepam, meclonazepam, and analogues are reported to establish the first structure-activity relationship for schistosomicidal benzodiazepines. Our findings indicate that the amide moiety [N(1) H-C(2) (=O)] is the principal pharmacophoric unit of 1,4-benzodiazepine schistosomicidal compounds and that substitution on the amide nitrogen atom (N(1) position) is not tolerated.

Surface active benzodiazepine-bromo-alkyl conjugate for potential GABAA-receptor purification.

A conjugable analogue of the benzodiazepine 5-(2-hydroxyphenyl)-7-nitro-benzo[e][1,4]diazepin-2(3H)-one containing a bromide C(12)-aliphatic chain (BDC) at nitrogen N1 was synthesized. One-pot preparation of this benzodiazepine derivative was achieved using microwave irradiation giving 49% yield of the desired product. BDC inhibited FNZ binding to GABA(A)-R with an inhibition binding constant K(i) = 0.89 µM and expanded a model membrane packed up to 35 mN m(-1) when penetrating in it from the aqueous phase. BDC exhibited surface activity, with a collapse pressure π = 9.8 mN m(-1) and minimal molecular area A(min) = 52 Å(2)/molecule at the closest molecular packing, resulted fully and non-ideally mixed with a phospholipid in a monolayer up to a molar fraction x≅ 0.1. A geometrical-thermodynamic analysis along the π-A phase diagram predicted that at low x(BDC) (<0.1) and at all π, including the equilibrium surface pressures of bilayers, dpPC-BDC mixtures dispersed in water were compatible with the formation of planar-like structures. These findings suggest that, in a potential surface grafted BDC, this compound could be stabilize though London-type interactions within a phospholipidic coating layer and/or through halogen bonding with an electron-donor surface via its terminal bromine atom while GABA(A)-R might be recognized through the CNZ moiety.