Pyridazinone hybrids: Design, synthesis and evaluation as potential anticonvulsant agents

Diverse Pharmacological Potential of Pyridazine Analogs against Various Diseases

Pyridazinone analogs possess diverse types of pharmacological activities, such as anticancer, antimicrobial, anticonvulsant, analgesic, anti-inflammatory, antioxidant, antihypertensive, antisecretory, antiulcer, and other useful pharmacological activities. They also possess cyclooxygenase (COX) inhibitors, dipeptidyl peptidase inhibitors, phosphodiesterase inhibitors, glutamate transporter activators, adenosine receptor antagonists, serotonin receptors antagonists, lipooxygenase, cholinesterase, vasodilator, and anesthetics. Pyridazine rings are the essential structure for some marketed drugs, such as pimobendan, levosimendan as a cardiotonic drug, and emorfozan as an analgesic and anti-inflammatory (Non-steroidal anti-inflammatory drug) agent. So, researchers all over the world have paid attention to synthesizing various pyridazinone compounds mainly due to the ease of design and synthesis of different analogs and variables in the pharmacological responses. This review article focuses on the pharmacological activities of different pyridazine analogs.

Synthesis, crystal structure, DFT, Hirshfeld surface analysis, energy framework, docking and molecular dynamic simulations of (E)-4-(4-methylbenzyl)-6-styrylpyridazin-3(2H)-one as anticancer agent

In this work, a novel crystal, (E)-4-(4-methylbenzyl)-6-styrylpyridazin-3(2H)-one (E-BSP) was synthesized via Knoevenagel condensation of benzaldehyde and (E)-6-(4-methoxystyryl)-4,5-dihydropyridazin-3(2H)-one. The molecular structure of E-BSP was confirmed by using FT-IR, 1H-NMR, 13C-NMR, UV-vis, ESI-MS, TGA/DTA thermal analyses and single crystal X-ray diffraction. The DFT/B3LYP methods with the 6-311++G(d,p) basis set were used to determine the vibrational modes over the optimized structure. Potential energy distribution (PED) and the VEDA 4 software were used to establish the theoretical mode assignments. The same approach was used to compute the energies of frontier molecular orbitals (HOMO-LUMO), global reactivity descriptors, and molecular electrostatic potential (MEP). Additionally, experimental and computed UV spectral parameters were determined in methanol and the obtained outputs were supported by FMO analysis. Molecular docking and molecular dynamics (MD) simulation analyses of the E-BSP against six proteins obtained from different cancer pathways were carried out. The proteins include; epidermal growth factor receptor (EGFR), Estrogen receptor (ERα), Mammalian target of rapamycin (mTOR), Progesterone receptor (PR) (Breast cancer), Human cyclin-dependent kinase 2 (CDK2) (Colorectal cancer), and Survivin (Squamous cell carcinoma/Non-small cell lung cancer). The results of the analyses showed that the compound had less binding energies ranging between -6.30 to -9.09 kcal/mol and formed stable complexes at the substrate-binding site of the proteins after the 50 ns MD simulation. Therefore, E-BSP was considered a potential inhibitor of different cancer pathways and should be used for the treatment of cancer after experimental validation and clinical trial.Communicated by Ramaswamy H. Sarma.

Synthesis, Spectroscopic Characterization, Antibacterial Activity, and Computational Studies of Novel Pyridazinone Derivatives

In this work, a novel series of pyridazinone derivatives (3-17) were synthesized and characterized by NMR (¹H and ¹³C), FT-IR spectroscopies, and ESI-MS methods. All synthesized compounds were screened for their antibacterial activities against Staphylococcus aureus (Methicillin-resistant), Escherichia coli, Salmonella typhimurium, Pseudomonas aeruginosa, and Acinetobacter baumannii. Among the series, compounds 7 and 13 were found to be active against S. aureus (MRSA), P. aeruginosa, and A. baumannii with the lowest MIC value range of 3.74-8.92 µM. Afterwards, DFT calculations of B3LYP/6-31++G(d,p) level were carried out to investigate geometry structures, frontier molecular orbital, molecular electrostatic potential maps, and gap energies of the synthesized compounds. In addition, the activities of these compounds against various bacterial proteins were compared with molecular-docking calculations. Finally, ADMET studies were performed to investigate the possibility of using of the target compounds as drugs.

Synthesis and characterization of new 5,5′-dimethyl- and 5,5′-diphenylhydantoin-conjugated hemorphin derivatives designed as potential anticonvulsant agents

Herein, the synthesis and characterization of some novel N-modified hybrid analogues of hemorphins containing a C-5 substituted hydantoin residue as potential anticonvulsants and for the blockade of sodium channels are presented.

Crystal structure and Hirshfeld surface analysis of 4-(2,6-di-chloro-benz-yl)-6-[(E)-2-phenyl-ethen-yl]pyridazin-3(2H)-one

The title pyridazinone derivative, C19H14Cl2N2O, an important pharmacophore with a wide variety of biological applications is not planar, the chloro-phenyl and pyridazinone rings being almost perpendicular, subtending a dihedral angle of 85.73 (11)°. The phenyl ring of the styryl group is coplanar with the pyridazinone ring [1.47 (12)°]. In the crystal, N-H⋯O hydrogen bonds form inversion dimers with an R 2 2(8) ring motif and C-H⋯Cl hydrogen bonds also occur. The roles of the inter-molecular inter-actions in the crystal packing were clarified using Hirshfeld surface analysis, and two-dimensional fingerprint plots indicate that the most important contributions to the crystal packing are from H⋯H (37.9%), C⋯H/H⋯C (18.7%), Cl⋯H/ H⋯Cl (16.4%) and Cl⋯C/C⋯Cl (6.7%) contacts.

Synthesis, spectroscopy, crystal structure, TGA/DTA study, DFT and molecular docking investigations of (E)-4-(4-methylbenzyl)-6-styrylpyridazin-3(2H)-one

In this study, we present the synthesis of novel pyridazin-3(2H)-one derivative namely (E)-4-(4-methylbenzyl)-6-styrylpyridazin-3(2H)-one (MBSP). The chemical structure of MBSP was characterized using spectroscopic techniques such as FT-IR, ¹H NMR, ¹³C NMR, UV-Vis, ESI-MS, and finally, the structure was confirmed by single X-ray diffraction studies. The DFT calculation was performed to compare the gas-phase geometry of the title compound to the solid-phase structure of the title compound. Furthermore, a comparative study between theoretical UV-Vis, IR, ¹H- and ¹³C NMR spectra of the studied compound and experimental ones have been carried out. The thermal behavior and stability of the compound were analyzed by using TGA and DTA techniques which revealed that the compound is thermostable up to its melting point. Finally, the in silico docking and ADME studies are performed to investigate whether MBSP is a potential therapeutic for COVID-19.

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.

Design, synthesis and docking studies of novel benzopyrone derivatives as anticonvulsants

A series of coumarin derivatives 6-8, 9a-h, 11 and 13a, b -16a, b was synthesized and screened for their anticonvulsant profile. Screening of these analogues using the 'gold standard methods' revealed variable anticonvulsant potential with remarkable effects observed particularly in chemically-induced seizure test. Compounds 6, 7, 13b disclosed the highest potency among the series with 100% protection against scPTZ. Quantification study confirmed that compound 6 (ED₅₀ 0.238 mmol/kg) was the most active congener in the scPTZ model and was approximately 1.5 folds more potent than ethosuximide as reference drug Meanwhile, in the MES test, candidate drugs exhibited mild to moderate anticonvulsant efficacy, the highest of which was compound 14a, imparting 50% protection at 2.1 mmol/kg, followed by other compounds with activity ranging from 14 to 33%, as compared to diphenylhydantoin. Additionally, all candidate compounds were screened for acute neurotoxicity using the rotarod method to identify motor impairment, where almost all compounds passed the test. Further neurochemical investigation was performed to unravel the effect of the most active compound (6) on GABA level in mouse brain, where a significant elevation was evident by 4 and 1.4 folds with respect to that of the control and reference groups at p < 0.05. Molecular modeling study using Discovery Studio program was performed, where compound 6 exhibited good binding interaction with γ-aminobutyric acid aminotransferase (GABA-AT) enzyme and this was consistent with the attained experimental results.

Polymorphism of 2-(5-benzyl-6-oxo-3-phenyl-1,6-di-hydro-pyridazin-1-yl)acetic acid with two monoclinic modifications: crystal structures and Hirshfeld surface analyses

Two polymorphs of the title compound, C19H16N2O3, were obtained from ethano-lic (polymorph I) and methano-lic solutions (polymorph II), respectively. Both polymorphs crystallize in the monoclinic system with four formula units per cell and a complete mol-ecule in the asymmetric unit. The main difference between the mol-ecules of (I) and (II) is the reversed position of the hy-droxy group of the carb-oxy-lic function. All other conformational features are found to be similar in the two mol-ecules. The different orientation of the OH group results in different hydrogen-bonding schemes in the crystal structures of (I) and (II). Whereas in (I) inter-molecular O-H⋯O hydrogen bonds with the pyridazinone carbonyl O atom as acceptor generate chains with a C(7) motif extending parallel to the b-axis direction, in the crystal of (II) pairs of inversion-related O-H⋯O hydrogen bonds with an R 2 2(8) ring motif between two carb-oxy-lic functions are found. The inter-molecular inter-actions in both crystal structures were analysed using Hirshfeld surface analysis and two-dimensional fingerprint plots.

Crystal structure, Hirshfeld surface analysis and DFT studies of 6-[(E)-2-(thio-phen-2-yl)ethenyl]-4,5-di-hydro-pyridazin-3(2H)-one

In the title compound, C10H10N2OS, the five atoms of the thio-phene ring are essentially coplanar (r.m.s. deviation = 0.0037 Å) and the pyridazine ring is non-planar. In the crystal, pairs of N-H⋯O hydrogen bonds link the mol-ecules into dimers with an R 2 2(8) ring motif. The dimers are linked by C-H⋯O inter-actions, forming layers parallel to the bc plane. The theoretical geometric parameters are in good agreement with XRD results. The inter-molecular inter-actions were investigated using a Hirshfeld surface analysis and two-dimensional fingerprint plots. The Hirshfeld surface analysis of the title compound suggests that the most significant contributions to the crystal packing are by H⋯H (39.7%), C⋯H/H⋯C (17.3%) and O⋯H/H⋯O (16.8%) contacts.

Crystal structure, Hirshfeld surface analysis and DFT studies of 2-[5-(4-methyl-benz-yl)-6-oxo-3-phenyl-1,6-di-hydro-pyridazin-1-yl]acetic acid

In the title compound, the phenyl and pyridazine rings are inclined to each other by 10.55 (12)°, whereas the 4-methyl­benzyl ring is nearly orthogonal to the pyridazine ring with a dihedral angle of 72.97 (10)°.

The title pyridazinone derivative, C₂₀H₁₈N₂O₃, is not planar. The phenyl ring and the pyridazine ring are inclined to each other by 10.55 (12)°, whereas the 4-methyl­benzyl ring is nearly orthogonal to the pyridazine ring, with a dihedral angle of 72.97 (10)°. In the crystal, mol­ecules are linked by pairs of O—H⋯O hydrogen bonds, forming inversion dimers with an R₂²(14) ring motif. The dimers are linked by C—H⋯O hydrogen bonds, generating ribbons propagating along the c-axis direction. The inter­molecular inter­actions were additionally investigated using Hirshfeld surface analysis and two-dimensional fingerprint plots. They revealed that the most significant contributions to the crystal packing are from H⋯H (48.4%), H⋯O/O⋯H (21.8%) and H⋯C/C⋯H (20.4%) contacts. Mol­ecular orbital calculations providing electron-density plots of HOMO and LUMO mol­ecular orbitals and mol­ecular electrostatic potentials (MEP) were also computed, both with the DFT/B3LYP/6–311 G++(d,p) basis set.

Crystal structure and Hirshfeld surface analysis of (E)-6-(4-hy-droxy-3-meth-oxy-styr-yl)-4,5-di-hydro-pyridazin-3(2H)-one

In the title com­pound, inter­molecular C—H⋯O, O—H⋯O and N—H⋯O hydrogen bonds link the mol­ecules into a three-dimensional supra­molecular network.

In the title com­pound, C₁₃H₁₄N₂O₃, the dihydropyridazine ring (r.m.s. deviation = 0.166 Å) has a screw-boat conformation. The dihedral angle between its mean plane and the benzene ring is 0.77 (12)°. In the crystal, inter­molecular O—H⋯O hydrogen bonds generate C(5) chains and N—H⋯O hydrogen bonds produce R₂²(8) motifs. These types of inter­actions lead to the formation of layers parallel to (12). The three-dimensional network is achieved by C—H⋯O inter­actions, including R₂⁴(8) motifs. Inter­molecular inter­actions were additionally investigated using Hirshfeld surface analysis and two-dimensional fingerprint plots. The most significant contributions to the crystal packing are by H⋯H (43.3%), H⋯C/C⋯H (19.3%), H⋯O/H⋯O (22.6%), C⋯N/N⋯C (3.0%) and H⋯N/N⋯H (5.8%) contacts. C—H⋯π inter­actions and aromatic π–π stacking inter­actions are not observed.

Crystal structure and Hirshfeld surface analysis of 4-(4-methyl-benz-yl)-6-phenyl-pyridazin-3(2H)-one

In this paper, we describe the synthesis of a new di-hydro-2H-pyridazin-3-one derivative. The mol-ecule, C18H16N2O, is not planar; the benzene and pyridazine rings are twisted with respect to each other, making a dihedral angle of 11.47 (2)°, and the toluene ring is nearly perpendicular to the pyridazine ring, with a dihedral angle of 89.624 (1)°. The mol-ecular conformation is stabilized by weak intra-molecular C-H⋯N contacts. In the crystal, pairs of N-H⋯O hydrogen bonds link the mol-ecules into inversion dimers with an R 2 2(8) ring motif. The inter-molecular inter-actions were investigated using Hirshfeld surface analysis and two-dimensional (2D) fingerprint plots, revealing that the most important contributions for the crystal packing are from H⋯H (56.6%), H⋯C/C⋯H (22.6%), O⋯H/H⋯O (10.0%) and N⋯C/C⋯N (3.5%) inter-actions.

Crystal structure and Hirshfeld surface analysis of ethyl 2-[5-(3-chloro-benz-yl)-6-oxo-3-phenyl-1,6-di-hydro-pyridazin-1-yl]acetate

The title pyridazinone derivative, C21H19ClN2O3, is not planar. The unsubstituted phenyl ring and the pyridazine ring are inclined to each other, making a dihedral angle of 17.41 (13)° whereas the Cl-substituted phenyl ring is nearly orthogonal to the pyridazine ring [88.19 (13)°]. In the crystal, C-H⋯O hydrogen bonds generate dimers with R 2 2(10) and R 2 2(24) ring motifs which are linked by C-H⋯O inter-actions, forming chains extending parallel to the c-axis direction. The inter-molecular inter-actions were investigated using Hirshfeld surface analysis and two-dimensional fingerprint plots, revealing that the most significant contributions to the crystal packing are from H⋯H (44.5%), C⋯H/H⋯C (18.5%), H⋯O/H⋯O (15.6%), Cl⋯H/H⋯Cl (10.6%) and C⋯C (2.8%) contacts.

Synthesis, in vivo and in silico evaluation of novel 2,3-dihydroquinazolin-4(1H)-one derivatives as potential anticonvulsant agents

In light of the pharmacophoric structural requirements for achieving anticonvulsant activity, a series of N-(1-methyl-4-oxo-2-un/substituted-1,2-dihydroquinazolin-3[4H]-yl)benzamide (4a-g) and N-(1-methyl-4-oxo-2-un/substituted-1,2-dihydroquinazolin-3[4H]-yl)-2-phenylacetamide (4h-n) derivatives were synthesized in two steps starting from the reaction of N-methyl isatoic anhydride with the appropriate hydrazide and followed by condensation with the appropriate aldehyde. The anticonvulsant activities of the synthesized compounds were evaluated according to the anticonvulsant drug development (ADD) programme protocol. Among the synthesized compounds, 4n showed promising activity in both the maximal electroshock (MES) and pentylenetetrazole (PTZ) tests with median effective dose (ED₅₀ ) values of 40.7 and 6 mg/kg, respectively. The six most promising derivatives, 4b, 4a, 4c, 4f, 4j, and 4i, showed very low ED₅₀ values in the PTZ test (3.1, 4.96, 8.68, 9.89, 12, and 13.53 mg/kg, respectively). All the tested compounds showed no to low neurotoxicity in the rotarod test with a wide therapeutic index. Docking studies of compound 4n suggested that GABA_A binding could be the mechanism of action of these derivatives. The in silico drug likeliness parameters indicated that none of the designed compounds violate Lipinski's rule of five and that they are able to cross the blood-brain barrier. Hit, Lead & Candidate Discovery.