Design, Synthesis and Enhanced BBB Penetration Studies of L-serine-Tethered Nipecotic Acid-Prodrug.

Nipecotic acid is considered to be one of the most potent inhibitors of neuronal and glial-aminobutyric acid (GABA) uptake in vitro. Due to its hydrophilic nature, nipecotic acid does not readily cross the blood-brain barrier (BBB). Large neutral amino acids (LAT1)-knotted nipecotic acid prodrug was designed and synthesized with the aim to enhance the BBB permeation by the use of carrier-mediated transport. The synthesized prodrug was tested in animal models of Pentylenetetrazole (PTZ)-induced convulsions in mice. Further pain studies were carried out followed by neurotoxicity estimation by writhing and rota-rod test respectively. HPLC data suggests that the synthesized prodrug has improved penetration through BBB. Nipecotic acid-L-serine ester prodrug with considerable anti-epileptic activity, and the ability to permeate the BBB has been successfully synthesized. Graphical Abstract.

Unraveling the Mechanism of cyclo-N5- Production through Selective C-N Bond Cleavage of Arylpentazole with Ferrous Bisglycinate and m-Chloroperbenzonic Acid: A Theoretical Perspective.

Very recently, the bulk synthesis of cyclo-N5- from arylpentazole through the treatment with m-chloroperbenzonic acid (m-CPBA) and ferrous bisglycinate ([Fe(Gly)2]) (Zhang, C., et al. Science 2017, 355, 374) has greatly promoted the application of pentazolate anion as a novel high-performance energetic material. Yet the mechanism for this reaction is still unexplored. Herein we perform mechanistic studies on the selective C-N bond cleavage in arylpentazole by using density functional theory methods. The direct C-N bond activation by m-CPBA was computed to be kinetically inaccessible. Instead, the oxidation of [Fe(Gly)2] by m-CPBA is much favorable, which leads to the generation of a high-valent iron(IV)-oxo product. The Fe(IV)-oxo intermediate has been examined by UV-vis absorption spectra experiments and further verified by excited-state calculations. It is found that the Fe(IV)-oxo serves as the key intermediate for the C-N bond activation of arylpentazole and the cyclo-N5- generation. Our calculations clarified the key mechanistic details of the cyclo-N5- generation, and the factors that affect the production yield are further discussed.

High-throughput brain activity mapping and machine learning as a foundation for systems neuropharmacology.

Technologies for mapping the spatial and temporal patterns of neural activity have advanced our understanding of brain function in both health and disease. An important application of these technologies is the discovery of next-generation neurotherapeutics for neurological and psychiatric disorders. Here, we describe an in vivo drug screening strategy that combines high-throughput technology to generate large-scale brain activity maps (BAMs) with machine learning for predictive analysis. This platform enables evaluation of compounds' mechanisms of action and potential therapeutic uses based on information-rich BAMs derived from drug-treated zebrafish larvae. From a screen of clinically used drugs, we found intrinsically coherent drug clusters that are associated with known therapeutic categories. Using BAM-based clusters as a functional classifier, we identify anti-seizure-like drug leads from non-clinical compounds and validate their therapeutic effects in the pentylenetetrazole zebrafish seizure model. Collectively, this study provides a framework to advance the field of systems neuropharmacology.

HPLC-Based Activity Profiling for GABAA Receptor Modulators in Extracts: Validation of an Approach Utilizing a Larval Zebrafish Locomotor Assay.

Gamma-aminobutyric acid type A (GABAA) receptors are major inhibitory neurotransmitter receptors in the central nervous system and a target for numerous clinically important drugs used to treat anxiety, insomnia, and epilepsy. A series of allosteric GABAA receptor agonists was identified previously with the aid of HPLC-based activity profiling, whereby activity was tracked with an electrophysiological assay in Xenopus laevis oocytes. To accelerate the discovery process, an approach has been established for HPLC-based profiling using a larval zebrafish (Danio rerio) seizure model induced by pentylenetetrazol (PTZ), a pro-convulsant GABAA receptor antagonist. The assay was validated with the aid of representative GABAergic plant compounds and extracts. Various parameters that are relevant for the quality of results obtained, including PTZ concentration, the number of larvae, the incubation time, and the data analysis protocol, were optimized. The assay was then translated into an HPLC profiling protocol, and active compounds were tracked in extracts of Valeriana officinalis and Magnolia officinalis. For selected compounds the effects in the zebrafish larvae model were compared with data from in silico blood-brain barrier (BBB) permeability predictions, to validate the use for discovery of BBB-permeable natural products.

Anticonvulsant effects of isomeric nonimidazole histamine H3 receptor antagonists.

Phenytoin (PHT), valproic acid, and modern antiepileptic drugs (AEDs), eg, remacemide, loreclezole, and safinamide, are only effective within a maximum of 70%-80% of epileptic patients, and in many cases the clinical use of AEDs is restricted by their side effects. Therefore, a continuous need remains to discover innovative chemical entities for the development of active and safer AEDs. Ligands targeting central histamine H3 receptors (H3Rs) for epilepsy might be a promising therapeutic approach. To determine the potential of H3Rs ligands as new AEDs, we recently reported that no anticonvulsant effects were observed for the (S)-2-(4-(3-(piperidin-1-yl)propoxy)benzylamino)propanamide (1). In continuation of our research, we asked whether anticonvulsant differences in activities will be observed for its R-enantiomer, namely, (R)-2-(4-(3-(piperidin-1-yl)propoxy)benzylamino)propaneamide (2) and analogs thereof, in maximum electroshock (MES)-, pentylenetetrazole (PTZ)-, and strychnine (STR)-induced convulsion models in rats having PHT and valproic acid (VPA) as reference AEDs. Unlike the S-enantiomer (1), the results show that animals pretreated intraperitoneally (ip) with the R-enantiomer 2 (10 mg/kg) were moderately protected in MES and STR induced models, whereas proconvulsant effect was observed for the same ligand in PTZ-induced convulsion models. However, animals pretreated with intraperitoneal doses of 5, 10, or 15 mg/kg of structurally bulkier (R)-enantiomer (3), in which 3-piperidinopropan-1-ol in ligand 2 was replaced by (4-(3-(piperidin-1-yl)propoxy)phenyl)methanol, and its (S)-enantiomer (4) significantly and in a dose-dependent manner reduced convulsions or exhibited full protection in MES and PTZ convulsions model, respectively. Interestingly, the protective effects observed for the (R)-enantiomer (3) in MES model were significantly greater than those of the standard H3R inverse agonist/antagonist pitolisant, comparable with those observed for PHT, and reversed when rats were pretreated with the selective H3R agonist R-(α)-methyl-histamine. Comparisons of the observed antagonistic in vitro affinities among the ligands 1-6 revealed profound stereoselectivity at human H3Rs with varying preferences for this receptor subtype. Moreover, the in vivo anticonvulsant effects observed in this study for ligands 1-6 showed stereoselectivity in different convulsion models in male adult rats.

Design, synthesis, anticonvulsant, and antiarrhythmic properties of novel N-Mannich base and amide derivatives of ß-tetralinohydantoin.

BACKGROUND: 5,5-Diphenylhydantoin (Phenytoin) is a well-known anticonvulsant and antiarrhythmic drug which may cause unwanted side effects. In order to avoid the adverse effects of phenytoin, especially on the central nervous and cardiovascular systems, two small series of amine derivatives (Mannich bases) and amide ones were designed containing ß-tetralinohydantoin system. In preliminary studies, some of arylpiperazinylmethyl derivatives with a ß-tetralinohydantoin moiety were effective in screening anticonvulsant tests in mice. METHODS: These new amine and amide derivatives of ß-tetralinohydantoin were evaluated in standard anticonvulsant screens (maximal electroshock (MES) or pentylenetetrazole (scPTZ) seizure tests) and their neurotoxicity was assessed in standardized rotarod tests. Additionally, due to structural features (a hydantoin ring), influence on antiarrhythmic activity, electrocardiogram components and blood pressure was tested in rats. RESULTS: The new N-Mannich bases were effective in maximal electroshock or pentylenetetrazole seizures screens; and the most interesting compound 4 (1-{[4-(1-phenyethyl)-piperazin-1-yl]methyl}-3',4'-dihydro-1'H,2H,5H-spiro[imidazolidine-4,2'-naphthalene]-2,5-dione) displayed anticonvulsant activity in both the aforementioned tests. Furthermore, compound 6, an amide derivative of ß-tetralinohydantoin, displayed significant antiarrhythmic activity in a barium chloride-induced arrhythmia model (ED50 16.3mg/kg), but it was devoid of anticonvulsant protection. None of the tested compounds affected the electrocardiogram components or blood pressure in normotensive rats. CONCLUSION: All new N-Mannich bases containing the ß-tetralinohydantoin system and 1-phenylalkylpiperazine were classified to Anticonvulsant Screening Program 1st class. In contrast, our results suggested that the introduction of an amide bond in the alkyl side chain of the ß-tetralinohydantoin system abolished the anticonvulsant activity, but not the antiarrhythmic one. However, further studies are required for a definitive conclusion.

Anticonvulsant activity of Citrus aurantium blossom essential oil (neroli): involvment of the GABAergic system.

Citrus aurantium L. blossoms are an important medicinal plant part in Iran and some other countries. It is used in traditional medicine as an antiseizure and anticonvulsant natural agent. Early in vitro research of the anticonvulsant activity of the blossom extracts were done but there has been no investigation focused on the blossom essential oil and its anticonvulsant activity. The anticonvulsant activity of the essential oil of C. aurantium blossoms (neroli) was investigated. The anticonvulsant activity of neroli was assessed in pentylenetetrazole (PTZ)-induced convulsion by i.v. and i.p. methods and maximal electroshock (MES) in mice, with diazepam as the standard drug. While mechanistic studies were conducted using flumazenil, a GABA A-benzodiazepine receptor complex site antagonist. Neroli produced protection against clonic by i.v adminiatration of PTZ at 20 and 40 mg/kg, compared with protection with benzodiazepine. The mean onset and percentage protection against convulsion in neroli-treated mice were reduced by flumazenil. Intraperitonaeal PTZ also decreased the latency of clonic seizure in the neroli (40 mg/kg) treated group. We also showed that neroli (20 and 40 mg/kg), exhibited inhibition of the tonic convulsion induced by MES and decreased the mortality rate. Neroli was analyzed by GC and GC-MS and twenty three constituents, representing 91.0 % of the chromatographical oil were identified. The major components of neroli were characterized as linalool (28.5%), linalyl acetate (19.6%), nerolidol (9.1%) E,E-farnesol (9.1%), α-terpineol (4.9%) and limonene (4.6%) which might be responsible for the anticonvulsant activity. The results suggest that neroli possesses biologically active constituent(s) that have anticonvulsant activity which supports the ethnomedicinal claims of the use of the plant in the management of seizure.

Use of the X-ray structure of the beta2-adrenergic receptor for drug discovery. Part 2: Identification of active compounds.

The recently published X-ray structures of the beta(2)-adrenergic receptor are the first examples of ligand-mediated GPCR crystal structures. We have previously performed computational studies that examine the potential viability of these structures for use in drug design, exploiting known ligand activities. Our previous study and a newly reported beta(2)/Timolol X-ray complex provide validation of the computational approaches. In the present work, we use the X-ray structures to extract, via in silico high-throughput docking, compounds from proprietary and commercial databases and demonstrate the successful identification of active compounds by radioligand binding.

Studies of the roles of NMDA and AMPA glutamate receptors in the mechanism of corasole convulsions in mice.

Experiments on mice were performed to study the ability of monocationic and dicationic adamantane and phenylcyclohexyl derivatives to prevent convulsive syndrome induced by i.p. corasole (pentylenetetrazole; 80 mg/kg). Monocationic phenylcyclohexyl derivatives, which are selective blockers of NMDA glutamate receptor channels, along with memantine and MK-801, effectively prevented the appearance of the clonic and tonic components of convulsions at micromolar concentrations. Their dicationic analogs, which block both NMDA and AMPA receptor channels, were ineffective against clonic convulsions, but prevented corasole-induced tonic convulsions at much lower concentrations. The convulsive action of corasole, whose primary target is weakening of the inhibitory action of GABA, appears to be mediated by glutamatergic synaptic transmission. NMDA receptors have a much greater involvement than AMPA receptors in the genesis of clonic convulsions, while AMPA receptor activation appears to be an important component of tonic convulsions.

Nitrogen lone pair interactions in organic molecules: a photoelectron spectroscopic study.

The electronic structure of several cyclic, saturated and unsaturated amines and imines has been investigated by UV photoelectron spectroscopy (UPS). The analysis of spectra has been performed with DFT and OVGF calculations and comparison with the UPS spectra of related compounds. The extent and type of nitrogen lone pair interactions is discussed because nitrogen lone pairs are the most important functional groups present in these molecules. The magnitude of interactions was found to depend on the spatial orientation and rigidity of mutual positions of the lone pairs, rather than on their spatial distance.

Espectro de acción antiepiléptica de la DL-4-hidroxi, 4-etil,4-fenil butiramida y sus homólogos inferiores / Profile of the antiepileptic action of DL-4-hydroxy, 4-ethyl, 4-phenyl butiramide and its inferior homologues

Se estudio la actividad farmacológica en animales de una serie nueva de compuestos anticonvulsionantes, la DL-4-hidroxil, 4-etil, 4-fenil butiramida (HEPB) y sus homólogos inferiores propionamida (HEPP) y acetamida (HEPA). La neurotoxidad fue determinada con un rotarod y se indujeron cuadros convulsivos con electrochoque supramáximo (MES), pentilentetrazol (TSC), estricnina (STR) y picrotoxina (PIC). HEPP es menos neurotóxica que HEPB y HEPA y altera el comportamiento de los ratones solamente a dosis altas. Los tres compuestos presentaron un amplio espectro de acción anticonvulsionante. Ellos son muy potentes para inhibir cuadros convulsivos inducidos con 4-AP, BIC, TSC y PTZ en dosis no tóxicas administradas ip, pero son inefectivas contra convulsiones inducidas con pic y STR. Los índices terapéuticos (IT = DT 50/D 50) fueron más elevados para HEPP. En consecuencia los resultados indican que los tres compuestos probados pueden servir para el tratamiento de convulsiones generalizadas tipo ausencias. Puesto que HEPP es el compuesto menos neurotóxico se ha seleccionado para los estudios toxicológicos y neuroquímicos