Design, synthesis, in vitro, and in vivo evaluation of novel phthalazinone-based derivatives as promising acetylcholinesterase inhibitors for treatment of Alzheimer's disease

Twenty novel phthalazinone-based compounds were designed as acetylcholinesterase (hAChE) inhibitors. Compounds 7e and 17c demonstrated comparable or superior activity compared to donepezil, respectively, in in vitro enzyme assay. Moreover, both compounds 7e and 17c possess minimal toxicity on hepatic and neuroblastoma cell lines. Besides, it was proved that compounds 7e and 17c have percentage alternations and a transfer latency time comparable to donepezil and can alleviate the cognitive impairment caused by the scopolamine-induced model in mice. The kinetic analysis for compound 17c suggested this compound as a mixed-type inhibitor that could bind to both the peripheral (PAS) and the catalytic site (CAS) of the hAChE enzyme. The synthesized molecules were subjected to in silico analyses, including molecular docking studies, and the outcomes were consistent with the in vitro findings.

Syntheses, crystal structures and Hirshfeld surface analysis of three salts of 1-(4-nitro-phenyl)-piperazine

The structures and Hirshfeld surface analysis of three salts of 1-(4-nitro-phenyl)-piperazine are discussed. In 4-(4-nitro-phen-yl)piperazin-1-ium salicylate (C₁₀H₁₄N₃O₂ ⁺·C₇H₅O₃ ^-), there are strong hydrogen bonds between cation and anion and the 4-nitro-phenyl substituent occupies an equatorial position in the piperazinium ring. The cation and anion are linked together by supra-molecular inter-actions [graph-set notation of hydrogen bonding (6) propagating in the a-axis direction]. Additionally, there is π-π stacking involving the salicylate anion and the piperazinium cation in adjacent asymmetric units as well as a C-H⋯π inter-action between a hydrogen atom on the piperazine ring and the phenyl ring within the salicyclate anion. In bis-[4-(4-nitro-phen-yl)piperazin-1-ium] bis-(4-fluoro-benzoate) trihydrate (2C₁₀H₁₄N₃O₂ ⁺·2C₇H₄FO₂ ^-·3H₂O), there are two cations, two anions, and three water mol-ecules of solvation in the asymmetric unit, all linked by hydrogen bonds [graph-set notation of hydrogen bonding R ² ₂(20) between adjacent cations and R ³ ₃(9) between a cation and its adjacent anion]. In the anion, the 4-nitro-phenyl ring occupies an axial substitution position in the piperazinium ring, which is relatively rare. Within the asymmetric unit, the phenyl groups in the cations show an offset π-π inter-action. Additionally, there is a C-H⋯π inter-action between a hydrogen atom on the phenyl ring within a cation and the phenyl ring within an anion. In 4-(4-nitro-phen-yl)piperazin-1-ium 3,5-di-nitro-benzoate (C₁₀H₁₄N₃O₂ ⁺·C₇H₄N₂O₆ ^-), there is a strong N-H⋯O hydrogen bond linking the cation and anion and the 4-nitro-phenyl ring occupies an axial substitution position in the piperazinium ring, as seen in the previous structure. In the crystal, the cation and the anion form a complex three-dimensional hydrogen-bonded array involving R ² ₂(8), R ⁴ ₄(12) and R ⁴ ₄(20) rings propogating in the a-axis direction. The nitro-phenyl group is disordered with occupancies of 0.806 (10) and 0.194 (10).

Inhibitory potential of nitrogen, oxygen and sulfur containing heterocyclic scaffolds against acetylcholinesterase and butyrylcholinesterase

Heterocycles are the key structures in organic chemistry owing to their immense applications in the biological, chemical, and pharmaceutical fields. Heterocyclic compounds perform various noteworthy functions in nature, medication, innovation etc. Most frequently, pure nitrogen heterocycles or various positional combinations of nitrogen, oxygen, and sulfur atoms in five or six-membered rings can be found. Inhibition of acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) enzymes is a popular strategy for the management of numerous mental diseases. In this context, cholinesterase inhibitors are utilized to relieve the symptoms of neurological illnesses like dementia and Alzheimer's disease (AD). The present review focuses on various heterocyclic scaffolds and their role in designing and developing new potential AChE and BChE inhibitors to treat AD. Moreover, a detailed structure-activity relationship (SAR) has been established for the future discovery of novel drugs for the treatment of AD. Most of the heterocyclic motifs have been used in the design of new potent cholinesterase inhibitors. In this regard, this review is an endeavor to summarize the biological and chemical studies over the past decade (2010-2022) describing the pursuit of new N, O and S containing heterocycles which can offer a rich supply of promising AChE and BChE inhibitory activities.

Crystal structures of six 4-(4-nitro-phenyl)-piperazin-1-ium salts

Six piperazinium salts, namely 4-(4-nitro-phenyl)-piperazin-1-ium 4-bromo-ben-zo-ate dihydrate, C10H14N3O2 +·C7H4BrO2 -·2H2O, (I), 4-(4-nitro-phenyl)-pi-per-a-zin-1-ium 4-iodo-benzoate dihydrate, C10H14N3O2 +·C7H4IO2 -·2H2O, (II), 4-(4-nitro-phenyl)-piperazin-1-ium 4-hy-droxy-benzoate monohydrate, C10H14N3O2 +·C7H5O3 -·H2O, (III), 4-(4-nitro-phenyl)-piperazin-1-ium 4-methyl-benzoate monohydrate, C10H14N3O2 +·C8H7O2 -·H2O, (IV), 4-(4-nitro-phenyl)-piperazin-1-ium 4-meth-oxy-benzoate hemihydrate, 2C10H14N3O2 +·2C8H7O3 -·H2O, (V), and 4-(4-nitro-phenyl)-piperazin-1-ium 4-eth-oxy-benzoate, 2C10H14N3O2 +·2C9H9O3 -, (VI), have been synthesized and their crystal structures solved by single-crystal X-ray diffraction, revealing that all of them crystallize in the triclinic space group P except for (V), which crystallizes in the monoclinic space group P21/c and has a disordered nitro group. Compounds (I) and (II) are isostructural. The crystal packing of (I)-(V) is constructed from organic chains formed by a combination of hydrogen bonds of type N-H⋯O and/or O-H⋯O and other weak inter-actions of type C-H⋯O and/or C-H⋯π, forming sheets, whereas (VI) shows a cationic and anionic-based layer structure.

Design and synthesis of novel coumarin derivatives as potential acetylcholinesterase inhibitors for Alzheimer's disease

Twenty novel 7-benzyloxycoumarin based compounds were synthesized with a variety of bioactive chemical fragments. The synthesized compounds showed remarkable acetylcholinesterase (AChE) inhibitory activity. In vitro assay revealed that compounds 7-benzyloxy-4-{[(4-phenylthiazol-2(3H)-ylidene)hydrazono]methyl}-2H-chromen-2-one (5b, IC₅₀= 0.451μM), 7-benzyloxy-4-({[4-(4-methoxyphenyl)thiazol-2(3H)-ylidene]hydrazono}methyl)-2H-chromen-2-one (5d, IC₅₀= 0.625μM), 5-amino-1-[2-(7-benzyloxy-2-oxo-2H-chromen-4-yl)acetyl]-1H-pyrazole-4-carbonitrile (13c, IC₅₀= 0.466μM), 2-(7-benzyloxy-2-oxo-2H-chromen-4-yl)-N-(2-methylimino-4-phenylthiazol-3(2H)-yl)acetamide (16a, IC₅₀= 0.500μM) and 2-(7-benzyloxy-2-oxo-2H-chromen-4-yl)-N-[4-(4-methoxyphenyl)-2-methyliminothiazol-3(2H)-yl]acetamide (16b, IC₅₀= 0.590μM) exhibited promising AChE inhibitory activity even better than donepezil (IC₅₀= 0.711μM). Kinetic study for compound 5b implied mixed type inhibitor which could bind peripheral anionic site (PAS) and catalytic active site (CAS) of AChE enzyme. In addition, in vivo evaluation of compounds 5b, 13c and 16a confirmed significant memory improvement in scopolamine-induced impairment model in tested mice. Furthermore, in silico studies were performed on the synthesized compounds which included molecular docking study at the active site of recombinant human acetylcholinesterase enzyme (rhAChE) as well as prediction of ADMET and other physicochemical parameters. A correlation between the docking results and IC₅₀ of tested compounds was routinely observed and shared similar binding pattern to the co-crystallized ligand donepezil.

Interplay of weak noncovalent interactions in alkoxybenzylidene derivatives of benzohydrazide and acetohydrazide: a combined experimental and theoretical investigation and lipoxygenase inhibition (LOX) studies

Three hydrazide-based Schiff bases have been synthesized and characterized by IR, UV-vis and X-ray diffraction methods. A detail analysis of intermolecular interactions has been performed by Hirshfeld surface analysis and DFT calculations.

Piperazine: A Promising Scaffold with Analgesic and Anti-inflammatory Potential

Piperazine, a nitrogen-containing heterocyclic has acquired an inimitable position in medicinal chemistry because of its versatile structure, which has fascinated researchers to design novel piperazine based molecules having various biological actions. The subsistence of various compounds possessing diverse pharmacological activities in the literature further confirms this fact. Currently available analgesics and anti-inflammatory drugs are associated with side effects that limit their use. Moreover, the literature reveals the incredible anti-inflammatory and analgesic potential of piperazine derivatives along with their method of synthesis, therefore; the present review has been designed to collate the development made in this area that will surely be advantageous in designing novel piperazine based candidates with enhanced efficacy and less toxicity. An extensive literature survey was carried by scrutinizing peer reviewed articles from worldwide scientific databases available on GOOGLE, SCOPUS, PUBMED, and only relevant studies published in English were considered.

In silico design of hydrazone antioxidants and analysis of their free radical-scavenging mechanism by thermodynamic studies

Background

Antioxidants are very crucial in maintaining the normal function of body cells, as they scavenge excess free radical in the body. A set of hydrazone antioxidants was designed by in silico screening. The density functional theory (DFT) method was employed to explore the reaction energetics of their free radical-scavenging mechanism. With the aid of the developed quantitative structure-activity relationship (QSAR) model for hydrazone antioxidants, the structure and antioxidant activity of these compounds were predicted. Three potential reaction mechanisms were investigated, namely, hydrogen atom transfer (HAT), single-electron transfer followed by proton transfer (SET-PT) and sequential proton loss electron transfer (SPLET). Bond dissociation enthalpy (BDE), adiabatic ionization potential (AIP), proton dissociation enthalpy (PDE), proton affinity (PA), electron transfer enthalpy (ETE) and Gibbs free energy that characterize the various steps in these mechanisms were calculated in the gas phase.

Results

A total of 25 hydrazone antioxidants were designed, in which the molecule MHD 017 gave the best antioxidant activity. Among the tested molecules, MHD 017 at the 10-OH site gave the best results for the various thermodynamic parameters calculated. The reaction Gibbs free energy results also indicate that this is the most favoured site for free radical scavenge.

Conclusion

The obtained results show that HAT and SPLET mechanisms are the thermodynamically plausible reaction pathways of free radical scavenge by hydrazone antioxidants. The reactivity of these compounds towards the hydroperoxyl radical (HOO·) was greater than that towards the methyl peroxyl radical (CH3OO·) based on the exergonicity of the calculated reaction Gibbs free energy.

Graphical abstract

Synthesis, X-Ray Crystal Structures, and Preliminary Antiproliferative Activities of New s-Triazine-hydroxybenzylidene Hydrazone Derivatives

We herein report a new small library of Schiff-base compounds that encompasses s-triazine and (2 or 4)-hydroxylbenzylidene derivatives. These compounds were synthesized through a hydrazone linkage connecting both the s-triazine and hydroxybenzylidene derivatives. The synthetic strategy adopted allowed the synthesis of the target compounds with excellent yields and purities as observed from their NMR (1H and 13C) and elemental analysis. Furthermore, 4f, 5b, and 5f were further confirmed by X-ray single crystal diffraction technique. The preliminary antiproliferative activities for the synthesized compounds were tested against two different cancer cell lines including breast cancer (MCF-7) and colon cancer (HCT-116). From the eighteen compounds, which have been examined, only two derivatives having piperidine moiety showed more selectivity against the two cell lines MCF-7 and HCT-116, while the others showed very weak activity. The position of the hydroxyl group in the benzylidine ring and the substituent on the s-triazine moiety has great effect on the activity of the prepared compounds. The IC50 values for the two derivatives 4a and 5a evaluated against breast cancer cells, very close to those for the chemotherapeutic drug cisplatin, are 27 µM (13.3 µg/mL), 17 µM (8.4 µg/mL), and 20 µM (6 µg/mL) for 4a, 5a, and cisplatin, respectively. These results propose the preliminary antiproliferative activity of these two derivatives may deserve further consideration for development of new derivatives as potent anticancer agents.

Ultrasonic Irradiation: Synthesis, Characterization, and Preliminary Antimicrobial Activity of Novel Series of 4,6-Disubstituted-1,3,5-triazine Containing Hydrazone Derivatives

Novel series of 4,6-disubstituted-1,3,5-triazines containing hydrazone derivatives were synthesized employing ultrasonic irradiation and conventional heating. The ultrasonication gave the target products in higher yields and purity in shorter reaction time compared with the conventional method. IR, NMR (H 1 and C 13), elemental analysis, and LC-MS confirmed the structures of the new products. The antimicrobial and antifungal activities were evaluated for all the prepared compounds against some selected Gram-positive and Gram-negative bacterial strains. The results showed that only two compounds 7i (pyridine derivative) and 7k (4-chlorobenzaldehyde derivative) displayed biological activity against some Gram-positive and Gram-negative bacteria, while the rest of the tested compounds did not display any antifungal activity.