Design, synthesis, pharmacological evaluation, and docking study of new acridone-based 1,2,4-oxadiazoles as potential anticonvulsant agents

Design, synthesis, and structure-activity relationships of five-membered heterocyclic incorporated aryl(alkyl)azoles: From antiproliferative thiazoles to safer anticonvulsant oxadiazoles

In the current study, a novel series of 1,2,4-oxadiazoles were designed, synthesized, and evaluated for their biological activities. A cell-based antiproliferative screening was accomplished on the newly synthesized 1,2,4-oxadiazoles along with our previously reported aryl(alkyl)azoles (AAAs) containing middle heterocyclic cores thiazole and oxazole. Among the tested compounds, naphthyl- thiazoles demonstrated higher antiproliferative activity and B3 was identified as the most potent compound with IC50 values in the range of 2.03-3.6 µM against SH-SY5Y neuroblastoma, HT-29 colorectal adenocarcinoma, and fibroblast cells (ten folds more potent than 5-FU and irinotecan). Further investigation revealed that B3 strongly inhibits tubulin polymerization with an IC50 of 0.79 µM, outperforming the reference drug colchicine (IC50 = 1.46 µM). In addition, evaluation of B3 on the expression level of BAX, BCL2, and CYCLIN D1 genes indicated the suppression of the cell cycle in the genome level. Interestingly, the 1,2,4-oxadiazole congeners displayed optimal anticonvulsant activity with significantly reduced cytotoxicity. Among the oxadiazole series, compound D4 featuring a 1,2,4-triazole head group demonstrated the highest activity in the maximal electroshock (MES) and pentylenetetrazol (PTZ) tests, with ED50 values of 2.23 and 24.60 mg/kg, respectively. In vivo evaluations suggested that D4 exerts its anticonvulsant effects by enhancing GABAA currents. In conclusion, our findings indicated that B3 in the thiazole congeners is a promising drug candidate for cancer treatment with a well-defined mechanism of action. Moreover, D4 and its congeners containing oxadiazole core are much safer anti-seizures which have potential for preclinical considerations as novel anticonvulsants.

Synthesis, Structural Modification, and Bioactivity Evaluation of Substituted Acridones as Potent Microtubule Affinity-Regulating Kinase 4 Inhibitors

Acridones present numerous pharmacological activities, including inhibition of microtubule affinity-regulating kinase 4 (MARK4) kinase activity. To investigate structure-activity relationships and develop potent MARK4 inhibitors, derivatives of 2-methylacridone were synthesized and tested for their activity against MARK4 kinase. Selective substitutions at the nitrogen atom were accomplished by treating 2-methylacridone with alkyl halides in the presence of K2CO3. In addition, amidation of acridone acetic acid 11 with piperazine or tryptophan methyl ester followed by derivatization with various amines gave a series of new acridone derivatives. Among the tested compounds, six were identified as possessing high inhibitory activity against MARK4. The molecular modeling studies showed that the derivatives bearing piperazine or tryptophan bind well to the ATP-binding site of MARK4. The antiproliferative activity of six active compounds was evaluated against HeLa and U87MG cancer cells. Tryptophan derivatives 23a, 23b, and 23c showed significant cytotoxicity against both cell lines with EC50 values ranging from 2.13 to 4.22 μM, while derivatives bearing piperazine were found to be not cytotoxic. Additionally, compound 23a decreased the proliferation of human MDA-MB-435 and U251 cancer cells in the low micromolar range; however, it also affects the non-cancerous HGF cells. Due to their high binding affinity against MARK4, the synthesized compounds could be potential agents to target MARK4 against cancer and tauopathies.

In silico molecular modeling, neuro-behavioral profile, and toxicity assessment of the essential oil of Ferula gummosa Boiss. as an anti-seizure agent

ETHNOPHARMACOLOGICAL RELEVANCE

Ferula gummosa Boiss., known in Persian as "Baridje," belongs to the Apiaceae family. All parts of this plant, especially the root, contain galbanum. Galbanum, the oleo-gum resin of F. gummosa, is one of the essential traditional herbal medicines in Iran, which is used as a tonic for epilepsy and chorea, memory enhancement, gastrointestinal diseases, and wound healing.

AIM OF THE STUDY

We investigated the toxicity, anticonvulsant effects, and molecular modeling of the essential oil (EO) distilled from the oleo-gum resin of F. gummosa.

MATERIALS AND METHODS

Gas chromatography-mass spectrometry was used to identify the EO components. The cytotoxicity of EO on HepG2 cell lines was assessed by the MTT method. Male mice were arranged as follows: negative control groups (sunflower oil (10 ml/kg, i.p.) or saline (10 ml/kg, p.o.)), EO groups (0.5, 1, 1.5, and 2.5 ml/kg, p.o.), and positive control groups (ethosuximide (150 mg/kg, p.o.) or diazepam (1.0 or 2 mg/kg, i.p.)). The motor coordination and neurotoxicity of EO were studied using the rota-rod test. Open-field, novel object recognition, and passive avoidance learning tests were used to investigate the effect of EO on locomotor activity and memory function. An acute pentylenetetrazole-induced seizure model was utilized to evaluate the anticonvulsant properties of the EO. The interaction of the EO main components with the GABA_A receptor was investigated by coarse-grained molecular dynamics simulations.

RESULTS

β-pinene, sabinene, α-pinene, and ρ-cymene were the main components of EO. The IC₅₀ of the EO at 24, 48, and 72 h was found to be 59.90, 12.96, and 3.93 μl/ml, respectively. No adverse effects were observed in memory, motor coordination, and locomotor activity in mice treated with EO. Administration of EO (1, 1.5, and 2.5 ml/kg) improved survival rates in mice receiving pentylenetetrazole (PTZ; to induce an epileptic seizure). Sabinene was able to bind to the binding site of benzodiazepines at the GABA_A receptor.

CONCLUSIONS

Acute treatment with the EO of F. gummosa caused antiepileptic effects and could effectively increase the survival rate in PTZ-treated mice with no significant toxicity.

Pyrimido[4,5-b]indole derivatives bearing 1,2,4-oxadiazole moiety as MDM2 inhibitor candidates in cancer treatment

Aim: In this study, novel hybrid structures of pyrimido-indole-oxadiazole were developed as MDM2 inhibitors for restoring the regular function of the p53. Materials & methods: A multistep chemical pathway was used to synthesize the derivatives. Nutlin-3a was used as a standard lead in molecular docking and molecular dynamics simulations. Finally, cytotoxicity was evaluated against MCF-7 cancer cells versus Doxorubicin. Results: The most promising candidate was 12c, which had an NO₂ group in the para position of the oxadiazole ring (IC₅₀: 1.1 μM). A satisfactory result was obtained with the combined application of 12c and Doxorubicin (IC₅₀ decreased to 0.63 μM), which could be potentially attributed to MDM2 inhibition. Conclusion: These hybrid structures can be further investigated as potential MDM2 inhibitors.

Anti-amoebic effects of synthetic acridine-9(10H)-one against brain-eating amoebae

Pathogenic A. castellanii and N. fowleri are opportunistic free-living amoebae. Acanthamoeba spp. are the causative agents of granulomatous amebic encephalitis (GAE) and amebic keratitis (AK), whereas Naegleria fowleri causes a very rare but severe brain infection called primary amebic meningoencephalitis (PAM). Acridinone is an important heterocyclic scaffold and both synthetic and naturally occurring derivatives have shown various valuable biological properties. In the present study, ten synthetic Acridinone derivatives (I-X) were synthesized and assessed against both amoebae for anti-amoebic and cysticidal activities in vitro. In addition, excystation, encystation, cytotoxicity, host cell pathogenicity was also performed in-vitro. Furthermore, molecular docking studies of these compounds with three cathepsin B paralogous enzymes of N. fowleri were performed in order to predict the possible docking mode with pathogen. Compound VII showed potent anti-amoebic activity against A. castellanii with IC₅₀ 53.46 µg/mL, while compound IX showed strong activity against N. fowleri in vitro with IC₅₀ 72.41 µg/mL. Compounds II and VII showed a significant inhibition of phenotypic alteration of A. castellanii, while compound VIII significantly inhibited N. fowleri cysts. Cytotoxicity assessment showed that these compounds caused minimum damage to human keratinocyte cells (HaCaT cells) at 100 µg/mL, while also effectively reduced the cytopathogenicity of Acanthamoeba to HaCaT cells. Moreover, Cathepsin B protease was investigated in-silico as a new molecular therapeutic target for these compounds. All compounds showed potential interactions with the catalytic residues. These results showed that acridine-9(10H)-one derivatives, in particular compounds II, VII, VIII and IX hold promise in the development of therapeutic agents against these free-living amoebae.

Novel spiro[indene-1,2'-quinazolin]-4'(3'H)-one derivatives as potent anticonvulsant agents: One-pot synthesis, in vivo biological evaluation, and molecular docking studies

A new series of spiro[indene-1,2'-quinazolin]-4'(3'H)-one derivatives 4a-m were synthesized via a one-pot method and evaluated for anticonvulsant activities using pentylenetetrazole (PTZ) and maximal electroshock (MES)-induced seizures. Obtained results demonstrated that these compounds have not anticonvulsant activity in PTZ test while are active in the MES test. Among the synthesized compounds, the best anticonvulsant activity was obtained with compound 4h. This compound also was not neurotoxic. Given that the title new compounds have the pharmacophore requirement for benzodiazepine (BZD) receptor agonist, the most potent compound was assayed in vivo and in silico as BZD receptor agonist. After treatment with flumazenil as a standard BZD receptor antagonist, anticonvulsant activity of compound 4h decreased. Therefore, the involvement of BZD receptors in anticonvulsant activity of this compound confirmed. Furthermore, docking study of compound 4h in the BZD-binding site of GABA_A receptor confirmed that this compound interacted with the important residues.

Synthesis and Evaluation of Antiproliferative Activity, Topoisomerase IIα Inhibition, DNA Binding and Non-Clinical Toxicity of New Acridine-Thiosemicarbazone Derivatives

In this study, we report the synthesis of twenty new acridine–thiosemicarbazone derivatives and their antiproliferative activities. Mechanisms of action such as the inhibition of topoisomerase IIα and the interaction with DNA have been studied for some of the most active derivatives by means of both in silico and in vitro methods, and evaluations of the non-clinical toxicities (in vivo) in mice. In general, the compounds showed greater cytotoxicity against B16-F10 cells, with the highest potency for DL-08 (IC₅₀ = 14.79 µM). Derivatives DL-01 (77%), DL-07 (74%) and DL-08 (79%) showed interesting inhibition of topoisomerase IIα when compared to amsacrine, at 100 µM. In silico studies proposed the way of bonding of these compounds and a possible stereoelectronic reason for the absence of enzymatic activity for CL-07 and DL-06. Interactions with DNA presented different spectroscopic effects and indicate that the compound CL-07 has higher affinity for DNA (Kb = 4.75 × 10⁴ M⁻¹; Ksv = 2.6 × 10³ M⁻¹). In addition, compounds selected for non-clinical toxicity testing did not show serious signs of toxicity at the dose of 2000 mg/kg in mice; cytotoxic tests performed on leukemic cells (K-562) and its resistant form (K-562 Lucena 1) identified moderate potency for DL-01 and DL-08, with IC₅₀ between 11.45 and 17.32 µM.

Design, Synthesis, and Evaluation of Anticonvulsant Activities of New Triazolopyrimidine Derivatives

Epilepsy, a severe brain disease affecting a large population, is treated mainly by antiepileptic drugs (AEDs). However, toxicity, intolerance, and low efficiency of the available AEDs have prompted the continual attempts in the discovery of new AEDs. In this study, we discovered a skeleton of triazolopyrimidine for the development of new AEDs. The design, synthesis, in vivo anticonvulsant activity evaluation of triazolopyrimidines (3a–3i and 6a–6e), and pyrazolopyrimidines (4a–4i) are reported. We found that most triazolopyrimidines showed anticonvulsive activity in the maximal electroshock (MES) and pentetrazol (PTZ)-induced seizure models. On the contrary, pyrazolopyrimidines (4a–4i) showed weak or no protective effects. Among the tested derivatives, compound 6d, holding a median effective dose (ED₅₀₎ of 15.8 and 14.1 mg/kg against MES and PTZ-induced seizures, respectively, was found to be the most potent one. Moreover, the protection index (PI) value of 6d was significantly higher than that of the available AEDs such as valproate, carbamazepine, and diazepam. The antiepileptic efficacy of compound 6d was also observed in the 3-mercaptopropionic acid and bicuculline-induced seizure models. Antagonistic effects of flumazenil and 3-MP for the anticonvulsive activity of 6d and also the radioligand-binding assay confirmed the involvement of GABA receptors, at least benzodiazepine (BZD) receptor, in the anticonvulsant activity of compound 6d. The docking study of compounds 4e and 6d with GABA_A receptor confirmed and explained their affinity to the BZD receptors.

Investigation of 1, 3, 4 Oxadiazole Derivative in PTZ-Induced Neurodegeneration: A Simulation and Molecular Approach

OBJECTIVE

The study investigated the effect 5-[(naphthalen-2-yloxy) methyl]-1,3,4-oxadiaszole2-thiol (B3) in animal model of acute epileptic shock.

METHODS

The pharmacokinetics profile of B3 was checked through SwissADME software. The binding affinities of B3, diazepam, and flumazenil (FLZ) were obtained through Auto Dock and PyRx. Post docking analysis and interpretation of hydrogen bonds were performed through Discovery Studio Visualizer 2016. Molecular dynamics simulations of three complexes were carried out through Desmond software package. B3 was then proceeded in PTZ-induced acute seizures models. Flumazenil was used in animal studies for elucidation of possible mechanism of B3. After behavioral studies, the animals were sacrificed, and the brain samples were isolated and stored in 4% formalin for molecular investigations including H and E staining, IHC staining and Elisa etc.

RESULTS

The results demonstrate that B3 at 20 and 40 mg/kg prolonged the onset time of generalized seizures. B3 considerably increased the expression of protective glutathione S-transferase and glutathione reductase and reduced lipid peroxidation and inducible nitric oxide synthase (P < 0.001) in the cortex. B3 significantly suppressed (P < 0.01) the over expression of the inflammatory mediator tumor necrosis factor-α, whose up-regulation is reported in acute epileptic shocks.

CONCLUSION

Hence, it is concluded from the aforementioned results that B3 provides neuroprotective effects PTZ-induced acute epileptic model. FLZ pretreatment resulted in inhibition of the anticonvulsant effect of B3. B3 possesses anticonvulsant effect which may be mediated through GABAA mediated antiepileptic pathway.

Pharmacological report of recently designed multifunctional coumarin and coumarin-heterocycle derivatives

Coumarin is a naturally available molecule and has been identified as a potent pharmacophore due to its pharmacological activity. Because of this, coumarin has been exploited synthetically to prepare a wide range of derivatives. In fact, most coumarin derivatives have been found to be less toxic, which is the most essential property for a drug molecule. Such molecules are being prepared for therapeutic use as broad-spectrum pharmacological agents. Microbial diseases including viral diseases have become very common and are responsible for many deaths worldwide. In particular, microbial drug resistance is a problem that needs to be tackled in an effective manner. Also, for Alzheimer's disease, which affects most elderly persons, no efficient chemotherapy exists. In addition, although diabetes, a metabolic syndrome, can be treated with many drugs, there is no complete cure. Thus, more potent antidiabetic agents are required for the management of diabetes. Likewise, for the treatment of a wide range of ailments caused by microbes, genetic factors, or lifestyle-related factors, an efficient drug regimen is needed. In view of this, coumarin derivatives are designed and evaluated. Here, coumarin derivatives that have been reported recently are compiled, classified and evaluated critically. This study briefly takes the structure-activity relationship into consideration and suggests the next suitable step. With a focus on the most potent molecules, the pharmacological activity of the evaluated molecules is described.

Synthesis of 5-arylacetylenyl-1,2,4-oxadiazoles and their transformations under superelectrophilic activation conditions

Acetylene derivatives of 1,2,4-oxadiazoles, i.e., 5-(2-arylethynyl)-3-aryl-1,2,4-oxadiazoles, have been obtained, for the first time reported, from 5-(2-arylethenyl)-3-aryl-1,2,4-oxadiazoles by their bromination at the carbon–carbon double bond followed by di-dehydrobromination with NaNH₂ in liquid NH₃. The reaction of the acetylenyl-1,2,4-oxadiazoles with arenes in neat triflic acid TfOH (CF₃SO₃H) at room temperature for 1 h resulted in the formation of E/Z-5-(2,2-diarylethenyl)-3-aryl-1,2,4-oxadiazoles as products of regioselective hydroarylation of the acetylene bond. The addition of TfOH to the acetylene bond of these oxadiazoles quantitatively resulted in E/Z-vinyl triflates. The reactions of the cationic intermediates have been studied by DFT calculations and the reaction mechanisms are discussed.

Conformational polymorphs of 3-cyclopropyl-5-(3-methyl-[1,2,4]triazolo[4,3-a]pyridin-7-yl)-1,2,4-oxadiazole

The dipharmacophore compound 3-cyclopropyl-5-(3-methyl-[1,2,4]triazolo[4,3-a]pyridin-7-yl)-1,2,4-oxadiazole, C₁₂H₁₁N₅O, was studied on the assumption of its potential biological activity. Two polymorphic forms differ in both their molecular and crystal structures. The monoclinic polymorphic form was crystallized from more volatile solvents and contains a conformer with a higher relative energy. The basic molecule forms an abundance of interactions with relatively close energies. The orthorhombic polymorph was crystallized very slowly from isoamyl alcohol and contains a conformer with a much lower energy. The basic molecule forms two strong interactions and a large number of weak interactions. Stacking interactions of the `head-to-head' type in the monoclinic structure and of the `head-to-tail' type in the orthorhombic structure proved to be the strongest and form stacked columns in the two polymorphs. The main structural motif of the monoclinic structure is a double column where two stacked columns interact through weak C-H...N hydrogen bonds and dispersive interactions. In the orthorhombic structure, a single stacked column is the main structural motif. Periodic calculations confirmed that the orthorhombic structure obtained by slow evaporation has a lower lattice energy (0.97 kcal mol^-1) compared to the monoclinic structure.

Application of Lanthanide Shift Reagent to the 1H-NMR Assignments of Acridone Alkaloids

This study investigates the application of the paramagnetic shift reagent tris(dipivaloylmethanato)-europium(III) in NMR spectral studies of permethoxyacridone alkaloids (1–3) and pyranoacridone alkaloids (4–6). The induced chemical shifts (∆δ) of all protons were observed for the same molecule, and were compared to deduce the positions resulting from the distance nearby the Eu(dpm)₃. Assignment of the H-2, H-4 and H-8 of polysubstituted acridones could be distinguished based on the least-squares method of lanthanide-induced shifts plotted against the mole ratios of Eu(dpm)₃ to the substrate. The developed method is not only potentially useful for determining the planar structures of polysubstituted compounds, such as acridones, anthraquinones, xanthones, flavonoids, and phenanthrenes, but also applicable for their stereochemistry.

Recent advancement in the discovery and development of anti-epileptic biomolecules: An insight into structure activity relationship and Docking

Although there have been many advancements in scientific research and development, the cause of epilepsy still remains an open challenge. In spite of high throughput research in the field of anti-epileptic drugs, efficacy void is still prevalent before the researchers. Researchers have persistently been exploring all the possibilities to curb undesirable side effects of the anti-epileptic drugs or looking for a more substantial approach to diminish or cure epilepsy. The drug development has shown a hope to medicinal chemists and researchers to carry further research by going through a substantial literature survey. This review article attempts to describe the recent developments in the anti-epileptic agents, pertaining to different molecular scaffolds considering their structure-activity relationship, docking studies and their mechanism of actions.

An In-Vivo Study on Anticonvulsant, Anxiolytic, and Sedative-Hypnotic Effects of the Polyphenol-Rich Thymus Kotschyanus Extract; Evidence for the Involvement of GABAA Receptors

Antidepressant-like activity of T. kotschyanus has been recently reported by scientists but insufficient attention has been so far devoted to T. kotschyanus, and there is a lack of information on the other neurobehavioral effects and side effects of this species. In the current study, the anticonvulsant, anxiolytic, and sedative-hypnotic, effects of Thymus kotschyanus extract on male NMRI mice were evaluated using pentylenetetrazole, maximal electroshock, elevated plus maze, and pentobarbital-induced sleeping tests. Since phenolic compounds and flavonoids have main roles in pharmacological effects of most plant extracts, the phenolic and flavonoid contents of the extract were measured with Folin-Ciocalteu and AlCl₃ reagents. Acute toxicity, passive avoidance, and open field tests were carried out to assess the toxicity of the extract. To find out the possible mechanism of action, flumazenil as the specific GABA_A receptor antagonist was used. Anticonvulsant and hypnotic effects of the extract were observed at 400 and 600 mg/kg. The extract at the dose of 200 mg/kg revealed significant anxiolytic effects, but it did not show any adverse effects on learning and memory at all the tested doses. Results of this study indicate that Thymus kotschyanus extract has anticonvulsant‎, anxiolytic, and hypnotic effects, which are likely related to the ability of some phenolic compounds to activate α1-containing GABA_A receptors but more experiments still need to be carried out in order to find the exact mechanism, active component, and the toxicity of the Thymus kotschyanus extract.

Synthesis and Evaluation of Anticonvulsant Activity of Some Schiff Bases of 7-Amino-1,3-dihydro-2H-1,4-benzodiazepin-2-one

A variety of 1,3-dihydro-2H-1,4-benzodiazepin-2-one azomethines and 1,3-dihydro-2H-1,4-benzodiazepin-2-one benzamide were prepared, characterized and evaluated for the anticonvulsant activity in the rat using picrotoxin-induced seizure model. The prepared 1,3-dihydro-2H-1,4-benzodiazepin-2-one azomethine derivatives emerged potentially anticonvulsant molecular scaffolds exemplified by compounds, 7-{(E)-[(4-nitrophenyl)methylidene]amino}-5-phenyl-1,3-dihydro-2H-1,4-benzodiazepin-2-one, 7-[(E)-{[4-(dimethylamino)phenyl]methylidene}amino]-5-phenyl-1,3-dihydro-2H-1,4-benzodiazepin-2-one, 7-{(E)-[(4-bromo-2,6-difluorophenyl)methylidene]amino}-5-phenyl-1,3-dihydro-2H-1,4-benzodiazepin-2-one and 7-[(E)-{[3-(4-fluorophenyl)-1-phenyl-1H-pyrazol-4-yl]methylidene}amino]-5-phenyl-1,3-dihydro-2H-1,4-benzodiazepin-2-one. All these four compounds have shown substantial decrease in the wet dog shake numbers and grade of convulsions with respect to the standard drug diazepam. The most active compound, 7-[(E)-{[4-(dimethylamino)phenyl]methylidene}amino]-5-phenyl-1,3-dihydro-2H-1,4-benzodiazepin-2-one, exhibited 74 % protection against convulsion which was higher than the standard drug diazepam. Furthermore, to identify the binding mode of the interaction amongst the target analogs and binding site of the benzodiazepine receptor, molecular docking study and molecular dynamic simulation were carried out. Additionally, in silico pharmacokinetic and toxicity predictions of target compounds were carried out using AdmetSAR tool. Results of ADMET studies suggest that the pharmacokinetic parameters of all the target compounds were within the acceptable range to become a potential drug candidate as antiepileptic agents.

An Overview of Coumarin as a Versatile and Readily Accessible Scaffold with Broad-Ranging Biological Activities

Privileged structures have been widely used as an effective template for the research and discovery of high value chemicals. Coumarin is a simple scaffold widespread in Nature and it can be found in a considerable number of plants as well as in some fungi and bacteria. In the last years, these natural compounds have been gaining an increasing attention from the scientific community for their wide range of biological activities, mainly due to their ability to interact with diverse enzymes and receptors in living organisms. In addition, coumarin nucleus has proved to be easily synthetized and decorated, giving the possibility of designing new coumarin-based compounds and investigating their potential in the treatment of various diseases. The versatility of coumarin scaffold finds applications not only in medicinal chemistry but also in the agrochemical field as well as in the cosmetic and fragrances industry. This review is intended to be a critical overview on coumarins, comprehensive of natural sources, metabolites, biological evaluations and synthetic approaches.

Synthetic and therapeutic perspectives of nitrogen containing heterocycles as anti-convulsants

Epilepsy is one of the commonly prevailing neurological disorders. According to the reports, it is evident that about 80% of the epileptic cases have been observed in developing countries. Although there are many drugs with significant potency available in the market; still there is an issue of selectivity and toxicity. Therefore, continuous attempts have been made by the researchers to develop newer therapeutic agents against epilepsy. Many synthetic strategies have been available in the literature to synthesize various classes of anticonvulsants with promising activity. In the presented review, authors have summarized some newer synthetic routes being used for the synthesis of nitrogen-containing anticonvulsants taking a cue from the reported established anticonvulsant drugs viz. vigabatrin, sodium valproate, oxcarbazepine, felbamate, retigabine, and gabapentin. Various derivatives with the substitution for better anticonvulsant profile have been described in the figures for easy comparative study. The structure-activity relationship (SAR) of compounds with maximum potency has also been discussed. This article may serve as a boost for the researchers to modify the pre-existing synthetic routes as well as to improve potency and yield of the compounds.

Novel 1,2,4-Oxadiazole Derivatives in Drug Discovery

Five-membered 1,2,4-oxadiazole heterocyclic ring has received considerable attentionbecause of its unique bioisosteric properties and an unusually wide spectrum of biological activities.Thus, it is a perfect framework for the novel drug development. After a century since the1,2,4-oxadiazole have been discovered, the uncommon potential attracted medicinal chemists'attention, leading to the discovery of a few presently accessible drugs containing 1,2,4-oxadiazoleunit. It is worth noting that the interest in a 1,2,4-oxadiazoles' biological application has been doubledin the last fifteen years. Herein, after a concise historical introduction, we present a comprehensiveoverview of the recent achievements in the synthesis of 1,2,4-oxadiazole-based compounds and themajor advances in their biological applications in the period of the last five years as well as briefremarks on prospects for further development.

Synthesis, cytotoxicity, and molecular docking of substituted 3-(2-methylbenzofuran-3-yl)-5-(phenoxymethyl)-1,2,4-oxadiazoles

A series of new benzofuran/oxadiazole hybrids (8a-n) was synthesized from 2H-chromene-3-carbonitriles (3a-c) through the multistep synthetic methodology, and these hybrids are known to exhibit anticancer activities. All the compounds were evaluated for their in vitro cytotoxicity against the HCT116 and MIA PaCa2 cell lines. Compounds 6a (IC₅₀ : 9.71 ± 1.9 μM), 6b (IC₅₀ : 7.48 ± 0.6 μM), and 6c (IC₅₀ : 3.27 ± 1.1 μM) displayed a significant cytotoxic activity, whereas compounds 8d and 8e exhibited good activity against both cell lines. The depletion of glycogen synthase kinase-3β (GSK3β) induces apoptosis through the inhibition of basal NF-κB activity in HCT116 colon cancer cells and MIA PaCa2 pancreatic cancer cells. Molecular docking of compounds 6a, 6b, 6c, 8d, and 8e with GSK3β demonstrated the best binding affinity, correlating with the biological activity assay. Furthermore, the structure-activity relationship of these novel compounds reveals promising features for their use in anticancer therapy.

Neuro-Behavioral Profile and Toxicity of the Essential Oil of Dorema ammoniacum Gum as an Anti-seizure, Anti-nociceptive, and Hypnotic Agent with Memory-enhancing Properties in D-Galactose Induced Aging Mice

In this study, we focused on the neuro-behavioral profile, toxicity, and possible mechanisms of action of Dorema ammoniacum gum essential oil (DAG-EO). For this purpose, passive avoidance and Y-maze tests were performed to evaluate the potential effect of DAG-EO in the attenuation of memory impairment induced by 49 days administration of D-galactose and acute injection of scopolamine. Anticonvulsant and anti-nociceptive activities of DAG-EO were evaluated in the pentylenetetrazole and ‎maximal electroshock-induced models of seizure and acetic acid-induced writhing tests, respectively. To find the possible mechanism of action, flumazenil and naloxone were used. Furthermore, the possible side effects were determined in the open field, grip strength, and ‎rotarod tests. Our findings supported that 7-day administration of DAG-EO (50 and 100 mg/kg) improves memory impairment induced following administration of D-galactose and scopolamine. It was also revealed that DAG-EO possesses a dose-dependent sedative-hypnotic (100 mg/kg), anticonvulsant (ED50 ≈ 170 mg/kg), and anti-nociceptive (ED50 ≈ 175 mg/kg) activities possibly mediated via directly and/or indirectly modulation of GABAA and opioid receptors. No side effect was observed except muscle relaxation which was less than that of diazepam. The output of this study confirms anti-seizure, anti-nociceptive, sedative-hypnotic, and memory-enhancing properties of DAG-EO by modulation of GABAA receptors.

Facile synthesis of N-1,2,4-oxadiazole substituted sulfoximines from N-cyano sulfoximines

A divergent approach has been successfully developed for the synthesis of N-1,2,4-oxadiazole substituted sulfoximines starting from N-cyano sulfoximines. This method has a wide degree of substrate scope that includes aryl, heteroaryl, alkyl, fluoroalkyl and saturated heterocyclic compounds. Excellent functional group tolerability was also observed. Extension of this methodology to nucleosides, amino acids and dipeptides was found to be successful. A gram scale reaction was also established. The major part of this method is metal free and the utility of environmentally friendly solvents such as 2-methyl THF and ionic liquids is an added advantage.

Design, Synthesis, In vitro Cytotoxic Activity Evaluation, and Study of Apoptosis Inducing Effect of New Styrylimidazo[1,2-a]Pyridines as Potent Anti-Breast Cancer Agents

BACKGROUND

This paper reports synthesis, cytotoxic activity, and apoptosis inducing effect of a novel series of styrylimidazo[1,2-a]pyridine derivatives.

OBJECTIVE

In this study, anti-cancer activity of novel styrylimidazo[1,2-a]pyridines was evaluated.

METHODS

Styrylimidazo[1,2-a]pyridine derivatives 4a-o were synthesized through a one-pot three-component reaction of 2-aminopyridines, cinnamaldehydes, and isocyanides in high yield. All synthesized compounds 4a-o were evaluated against breast cancer cell lines including MDA-MB-231, MCF-7, and T-47D using MTT assay. Apoptosis was evaluated by acridine orange/ethidium bromide staining, cell cycle analysis, and TUNEL assay as the mechanism of cell death.

RESULTS

Most of the synthesized compounds exhibited more potent cytotoxicity than standard drug, etoposide. Induction of apoptosis by the most cytotoxic compounds 4f, 4g, 4j, 4n, and 4m was confirmed through mentioned methods.

CONCLUSION

In conclusion, these results confirmed the potency of styrylimidazo[1,2-a]pyridines for further drug discovery developments in the field of anti-cancer agents.

One-pot synthesis of 3,5-diaryl substituted-1,2,4-oxadiazoles using gem-dibromomethylarenes

1,2,4-Oxadiazole is one of the most promising heterocyclic ring systems in medicinal chemistry. In the present paper, we report the method for an efficient one-pot synthesis of 3,5-diaryl substituted 1,2,4-oxadiazoles using a two-component reaction of gem-dibromomethylarenes with amidoximes in good yields. In this method, gem-dibromomethylarenes are used as benzoic acid equivalents for the efficient synthesis of aryl-substituted 1,2,4-oxadiazoles. It is anticipated that this methodology will have versatile applications in the practical syntheses of various molecules of both medicinal and material chemistry importance.

MPMT-OX up-regulates GABAergic transmission and protects against seizure-like behavior in Caenorhabditis elegans

The signal transmission in the nervous system operates through a sensitive balance between excitatory (E) inputs and inhibitory (I) responses. Imbalances in this system contribute to the development of pathologies such as seizures. In Caenorhabditis elegans, the locomotor circuit operates via the coordinated activity of cholinergic excitatory (E) and GABAergic inhibitory (I) transmission. Changes in E/I inputs can cause uncontrolled electrical discharges, mimicking the physiology of seizures. Molecules derived from 1,3,4-oxadiazole have been found to exhibit diverse biological activities, including anticonvulsant effect. In this work, we study the activity of the compound 2-[(4-methoxyphenylselenyl)methylthio]-5-phenyl-1,3,4-oxadiazole (MPMT-OX) in the GABAergic and cholinergic systems. We demonstrate that MPMT-OX reduced the locomotor activity of C. elegans with a normal balance between the E/I systems and increased the resistance to paralysis in worms exposed to pentylenetetrazol and aldicarb. MPMT-OX increased seizure resistance and assisted in the recovery of locomotor activity in worms with deletions in the genes unc-46, which regulates the transport of GABA into vesicles, and unc-49, which encodes the GABA_A receptor. C. elegans with deletions in the unc-25 and unc-47 genes did not respond to treatment. Therefore, we suggest that the compound MPMT-OX upregulates GABAergic signaling in a manner dependent on the unc-25 gene, which is responsible for GABA synthesis, and unc-47, which encodes the vesicular GABA transporter.

Design, synthesis, and evaluation of anticonvulsant activities of benzoxazole derivatives containing the 1,2,4-triazolone moiety

A novel series of benzoxazole derivatives containing 1,2,4-triazolone (5a-m) was designed. These compounds were synthesized in order to screen their anticonvulsant activities by the maximal electroshock seizure (MES) model and the subcutaneous pentylenetetrazole (sc-PTZ) seizure model in mice. The rotarod test was used to evaluate their neurotoxicities. Most of the compounds showed anti-MES activities at 100 and 300 mg/kg. Compound 5f, which showed potential anticonvulsant activity in the MES model with ED₅₀ values of 22.0 mg/kg, was considered as the most promising one in this study. It exhibited greater safety than that of carbamazepine and valproate regarding neurotoxicity. The efficacy of compound 5f in inhibiting the tonic seizures and death induced by the convulsants 3-mercaptopropionic acid and BIC was also verified. In an enzyme-linked immunosorbent assay, compound 5f and the positive drug phenytoin significantly increased the γ-aminobutyric acid (GABA) level in the mouse brain. Further, pretreatment with an inhibitor of the GABA synthesizing enzyme dramatically raised the ED₅₀ value of 5f in the MES model. These results confirmed that the compound 5f plays its anticonvulsive action via regulating the GABA function in the brain. Also, a docking study of the compound 5f in the benzodiazepine (BZD) binding site of the GABA_A receptor confirmed possible binding of the compound 5f with BZD receptors.

Design, Synthesis and Cytotoxicity of Novel Coumarin-1,2,3-triazole-1,2,4- Oxadiazole Hybrids as Potent Anti-breast Cancer Agents

Background:

This work reports design, synthesis, and in vitro cytotoxicity of novel coumarin-1,2,3-triazole-1,2,4-oxadiazole hybrids against three breast cancer cell lines MCF-7, MDA-MB-231, and T-47D.

Methods:

Synthetic procedure for the preparation of desired compounds was started from the reaction of coumarins or with propargyl bromide to give O-propargylated coumarins or 5. Then, click reaction between the later compounds and 3-aryl-5-(chloromethyl)-1,2,4-oxadiazoles afforded the desired products in good yields.

Results:

Among the synthesized compounds, 4-((1-((3-(4-chlorophenyl)-1,2,4-oxadiazol-5- yl)methyl)-1H-1,2,3-triazol-4-yl)methoxy)-2H-chromen-2-one (9a) showed the best cytotoxicity against breast cancer cell lines.

Conclusion:

Compound 9a depicted the most activity toward MDA-MB-231 and T-47D cells while compounds 8a and 8c were the most potent compounds against MCF-7.

Design, synthesis, in vivo, and in silico evaluation of new coumarin-1,2,4-oxadiazole hybrids as anticonvulsant agents

A novel series of coumarin-1,2,4-oxadiazole hybrids were designed, synthesized, and evaluated as anticonvulsant agents. The title compounds were easily synthesized from reaction of appropriate coumarins and 3-aryl-5-(chloromethyl)-1,2,4-oxadiazole derivatives. In vivo anticonvulsant activity of the synthesized compounds were determined using pentylenetetrazole (PTZ)- and maximal electroshock (MES)-induced seizures confirming that they were more effective against MES test than PTZ test. It should be noted that compounds 3b, 3c, and 3e showed the best activity in MES model which possessed drug-like properties with no neurotoxicity. Anticonvulsant activity of the most potent compound 3b was remarkably reduced after treatment with flumazenil which confirmed the participation of a benzodiazepine mechanism in the anticonvulsant activity. Also, docking study of compound 3b in the BZD-binding site of GABA_A receptor confirmed possible binding of 3b to the BZD receptors.

A Review Exploring Therapeutic Worth of 1,3,4-Oxadiazole Tailored Compounds

1,3,4-Oxadiazole, a five-membered aromatic ring can be seen in a number of synthetic molecules. The peculiar structural feature of 1,3,4-oxadiazole ring with pyridine type of nitrogen atom is beneficial for 1,3,4-oxadiazole derivatives to have effective binding with different enzymes and receptors in biological systems through numerous weak interactions, thereby eliciting an array of bioactivities. Research in the area of development of 1,3,4-oxadiazole-based derivatives has become an interesting topic for the scientists. A number of 1,3,4-oxadiazole based compounds with high therapeutic potency are being extensively used for the treatment of different ailments, contributing to enormous development value. This work provides a systematic and comprehensive review highlighting current developments of 1,3,4-oxadiazole based compounds in the entire range of medicinal chemistry such as anticancer, antifungal, antibacterial, antitubercular, anti-inflammatory, antineuropathic, antihypertensive, antihistaminic, antiparasitic, antiobesity, antiviral, and other medicinal agents. It is believed that this review will be of great help for new thoughts in the pursuit for rational designs for the development of more active and less toxic 1,3,4-oxadiazole based medicinal agents.

Neuropharmacokinetics: a bridging tool between CNS drug development and therapeutic outcome

WHO classified neurological disorders to be among 6.3% of the global disease burden. Among the most central aspects of CNS drug development is the ability of novel molecules to cross the blood-brain barrier (BBB) to reach the target site over a desired time period for therapeutic action. Based on various aspects, brain pharmacokinetics is considered to be one of the foremost perspectives for the higher attrition rate of CNS biologics. Although drug traits are important, the BBB and blood-cerebrospinal fluid barrier together with transporters become the mechanistic approach behind CNS drug delivery. The present review emphasizes neuropharmacokinetic parameters, their importance, an assessment approach and the vast effect of transporters to brain drug distribution for CNS drug discovery.

Pyrano[3,2-c]quinoline Derivatives as New Class of α-glucosidase Inhibitors to Treat Type 2 Diabetes: Synthesis, in vitro Biological Evaluation and Kinetic Study

BACKGROUND

Pyrano[3,2-c]quinoline derivatives 6a-n were synthesized via simple two-step reactions and evaluated for their in vitro α-glucosidase inhibitory activity.

METHODS

Pyrano[3,2-c]quinoline derivatives 6a-n derivatives were prepared from a two-step reaction: cycloaddition reaction between 1-naphthyl amine 1 and malonic acid 2 to obtain benzo[h]quinoline-2(1H)-one 3 and reaction of 3 with aryl aldehydes 4 and Meldrum's acid 5. The anti- α-glucosidase activity and kinetic study of the synthesized compounds were evaluated using α-glucosidase from Saccharomyces cerevisiae and p-nitrophenyl-a-D-glucopyranoside as substrate. The α-glucosidase inhibitory activity of acarbose was evaluated as positive control.

RESULTS

All of the synthesized compounds, except compounds 6i and 6n, showed more inhibitory activity than the standard drug acarbose and were also found to be non-cytotoxic. Among the synthesized compounds, 1-(2-bromophenyl)-1H-benzo[h]pyrano[3,2-c]quinoline-3,12(2H,11H)-dione 6e displayed the highest α-glucosidase inhibitory activity (IC50 = 63.7 ± 0.5 µM). Kinetic study of enzyme inhibition indicated that the most potent compound, 6e, is a non-competitive inhibitor of α-glucosidase with a Ki value of 72 µM. Additionally, based on the Lipinski rule of 5, the synthesized compounds were found to be potential orally active drugs.

CONCLUSION

Our results suggest that the synthesized compounds are promising candidates for treating type 2 diabetes.

A Straightforward and High-Yielding Synthesis of 1,2,4-Oxadiazoles from Chiral N-Protected α-Amino Acids and Amidoximes in Acetone-Water: An Eco-Friendly Approach

A straightforward and high-yielding methodology for the synthesis of a high structural diversity of 1,2,4-oxadiazoles from different chiral N-protected α-amino acids and amidoximes under microwave (MW) irradiation is described herein. This greener approach gives the desired products using acetone/water as solvent in very short reaction times.