A multifunctional therapeutic approach: Synthesis, biological evaluation, crystal structure and molecular docking of diversified 1H-pyrazolo[3,4-b]pyridine derivatives against Alzheimer's disease

Antioxidants in anti-Alzheimer's disease drug discovery

Oxidative stress is widely recognized as a key contributor to the pathogenesis of Alzheimer's disease (AD). While not the sole factor, it is closely linked to critical pathological features, such as the formation of senile plaques and neurofibrillary tangles. The development of agents with antioxidant properties has become an area of growing interest in AD research. Between 2015 and 2024, several antioxidant-targeted drugs for AD progressed to clinical trials, with increasing attention to the evaluation of antioxidant properties during their development. Oxidative stress plays a pivotal role in linking various AD hypotheses, underscoring its importance in understanding the disease mechanisms. Despite this, comprehensive reviews addressing advancements in AD drug development from the perspective of antioxidant capacity remain limited, hindering the design of novel compounds. This review aims to explore the mechanistic relationship between oxidative stress and AD, summarize methods for assessing antioxidant capacity, and provide an overview of antioxidant compounds with anti-AD properties reported over the past decade. The goal is to offer strategies for identifying effective antioxidant-based therapies for AD and to deepen our understanding of the role of oxidative stress in AD pathology.

Unveiling piperazine-quinoline hybrids as potential multi-target directed anti-Alzheimer's agents: design, synthesis and biological evaluation

Multi-target directed ligands (MTDLs) have recently been popularized due to their outstanding efficacy in combating the complicated features of Alzheimer's disease. This study details the synthesis of piperazine-quinoline-based MTDLs through a multicomponent Petasis reaction, targeting multiple factors such as AChE, BuChE, metal chelation to restore metal dyshomeostasis, and antioxidant activity. Some of the synthesized compounds exhibited notable inhibitory activity against AChE and BuChE enzymes at specific concentrations. Among the synthesized compounds compound (95) containing a 4-chloroaniline moiety and a 4-methoxybenzyl group displayed the most promising inhibitory activities against AChE (IC50 3.013 µM) and BuChE (IC50 = 3.144 µM). Compound (83) featuring 2-methoxyaniline and 4-fluorobenzyl substituents, exhibited the highest BuChE inhibition (IC50 1.888 µM). Notably, compound (79) demonstrated 93-times higher selectivity for BuChE over AChE. Molecular docking and molecular dynamics simulations were also performed to explore the binding modes and stability of these compounds with the AChE amd BuChE proteins. Further, kinetics study was performed against AChE for comounds (83 and 95) which indicated mixed inhibition of the enzyme by these compounds, Amongs the synthesized compounds, nine compounds were assessed for their antioxidant activity, displaying significant antioxidant properties with IC50 values ranging from 156 µM to 310 µM. Moreover, all the compounds demonstrated metal chelating tendency with Cu+2, Zn+2, Fe+2, Fe+3 and Al+3. This study provides insights into the design of novel MTDLs, highlighting compound (95) as a potential candidate for combating Alzheimer's disease.

Analysis of skeletal diversity of multi-target directed ligands (MTDLs) targeting Alzheimer's disease

Alzheimer's disease (AD) remains a significant healthcare challenge, necessitating innovative therapeutic approaches to address its complex and multifactorial nature. Traditional drug discovery strategies targeting single molecular targets are not sufficient for the effective treatment of AD. In recent years, MTDLs have emerged as promising candidates for AD therapy, aiming to simultaneously modulate multiple pathological targets. Among the various strategies employed in MTDL design, pharmacophore hybridization offers a versatile approach to integrate diverse pharmacophoric features within a single molecular scaffold. This strategy provides access to a wide array of chemical space for the design and development of novel therapeutic agents. This review, therefore, provides a comprehensive overview of skeletal diversity exhibited by MTDLs designed recently for AD therapy based on pharmacophore hybridization approach. A diverse range of pharmacophoric elements and core scaffolds hybridized to construct MTDLs that has the potential to target multiple pathological features of AD including amyloid-beta aggregation, tau protein hyperphosphorylation, cholinergic dysfunction, oxidative stress, and neuroinflammation are discussed. Through the comprehensive analysis and integration of structural insights of key biomolecular targets, this review aims to enhance optimization efforts in MTDL design, ultimately striving towards a comprehensive cure for the multifaceted pathophysiology of the disease.

In Silico Study, Synthesis, and In Vitro Evaluation of Acetylcholinesterase and Butyrylcholinesterase Inhibitory Activity of Novel N-Thiazole Substituted Acetamide Coumarin Derivatives

In this study, a structurally directed pharmacophore hybridization technique is used to combine the two essential structural scaffolds coumarin and thiazoles in search of a new class of acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) inhibitor for Alzheimer's disease (AD). A library of 120 compounds was designed in two series 5a(1-15), 5b(16-30), 5c(31-45), 5d(46-60), and 6a(61-75), 6b(76-90), 6c(91-105), 6d(106-120) using various substituted phenol, β-ketoesters, and thiazole derivatives. Eleven compounds were identified as potential hybrids using molecular property filter analysis and molecular docking studies, and they comprise N-substituted thiazole coumarin derivatives. The docking results indicated that compounds 5b16 and 5c35 exhibited strong binding interactions with GLY116, GLY117, TYR332, and HIS438 (ranging from -27.42 to -24.18 kcal/mol) and GLY119, ASP72, and PHE288 (ranging from -32.21 to -25.92 kcal/mol) when tested against AChE (1EVE) and BuChE (1P0I) inhibitors. These compounds were synthesized via conventional methods and characterized by different spectroscopic methods. In vitro anti-cholinesterase activity results indicated that two compounds, for example, 5b16 and 5c35 showed potent to moderate activity against AChE and BuChE with IC50 (2.00 ± 0.09-29.63 ± 0.48) µM and (34.93 ± 0.62-17.92 ± 0.42) µM, respectively. Our study demonstrated the development of a novel class of hybrid coumarin thiazole derivatives as AChE and BuChE inhibitors, and these compounds could be utilized against ADs.

Computational analysis of Urolithin A as a potential compound for anti-inflammatory, antioxidant, and neurodegenerative pathways

Urolithin A, an active precursor derived from the metabolism of ellagitanins in rats and humans, is known for its potential health benefits, including stimulating mitophagy and promoting muscular skeletal function. While experimental studies have demonstrated Urolithin A's potential to enhance cellular health, the detailed molecular interactions through which Urolithin A exerts its effects are not fully elucidated. In this study, we investigated the anti-inflammatory, antioxidation and neuroprotective abilities of Urolithin A in selected targets using molecular docking and molecular dynamics simulation methods. Molecular docking studies revealed the strong affinity for receptors involved in inflammation activities, including human p38 MAP kinase (4DLI) with -10.1 kcal/mol interacting with SER252, LYS249, and ASP294 residues. The binding energy in the 5KIR target was -8.6 kcal/mol, interacting with GLN203 through hydrogen bond, and lastly, 1A9U with an affinity of -6.8 with no hydrogen bond formed with Urolithin A and interacts with van der Waals interactions. In oxidant targets, the influence of Urolithin was observed in 1OG5 with -7.9 kcal/mol interacting with GLN185, PHE447. For the 1M17 target, the binding affinity was -7.7 kcal/mol interacting with THR95 residue and 1ZXM target at -7.4 kcal/mol interacting with TYR36, TYR216, and LEU234 residues. The neuroprotective ability of urolithin A was observed in selected targets for acetylcholinesterase; the binding energy was -9.7 kcal/mol interacting with van der Waals and π interactions; for the 1GQR target, the binding energy was -9.9 kcal/mol interacting with van der Waals and π interactions and for β-amylase (1iyt) the binding energy was -5.5 forming hydrogen bond with SER8, GLN15 residues. Molecular Dynamics simulations at 100 ns of Urolithin A compared with reference 4DLI. The Urolithin A-4DLI complex exhibited greater stability than the reference receptor, as confirmed by RMSD, RMSF, Radius of Gyration, Hydrogen bond, and SASA analyses.

Design, synthesis and biological evaluation of novel pyrazolinone derivatives as multifunctional ligands for the treatment of Alzheimer's disease

Alzheimer's disease (AD) is a progressive neurodegenerative disorder characterized by the depletion of cholinergic neurons and the accumulation of amyloid β (Aβ) plaques. The complexity and multifaceted nature of AD necessitate further exploration of multi-target drugs for its treatment. In this study, a series of novel pyrazolinone-based compounds were designed, synthesized, and evaluated as acetylcholinesterase (AChE) inhibitors and antioxidants. The lead compounds ET11 and ET21 showed strong inhibitory activity against human AChE, with IC50 values of 6.34 and 1.81 nM, respectively. In vitro DPPH and ORACFL assays confirmed the compounds' strong antioxidant capabilities. ET11 exhibited excellent neuroprotective activity in the tBHP-induced SH-SY5Y cell damage model. Benefiting from the pyridopyrazolone moiety, ET11 showed significant Cu2+ chelating ability and effectively inhibited Cu2+-induced Aβ aggregation. In vivo behavioral studies and histopathology analysis preliminarily confirmed the compound's cognitive improvement and neuroprotective effects. Overall, these findings suggested that compound ET11 is expected to play a synergistic role in the treatment of AD, potentially slowing disease progression.

Rational design, synthesis and computational studies of multi-targeted anti-Alzheimer's agents integrating coumarin scaffold

The traditional theory of "one drug, one target, one illness" has come under scrutiny owing to the multifactorial nature of Alzheimer's disease (AD) and the failure of most of its medications, therefore multi-target directed ligands (MTDLs) are prospective therapeutics for AD. In the present study, we synthesized novel series of coumarin derivatives and assessed their inhibitory actions against hAChE, hBuChE, GSK-3β, tau protein and Aβ aggregation. Compounds 6c and 6h stood out among the others with their multifunctional profile. With IC50 values of 28.88 and 26.03 nM, respectively, compounds 6c and 6h showed outstanding activity as hAChE inhibitors and demonstrated good inhibitory activity against hBuChE with IC50 values of 103.90 and 90.09 nM along with appropriate action against GSK-3β in nanomolar range. Also, both compounds 6c and 6h were found to outperform the reported anti-AD donepezil as tau protein aggregation and amyloid aggregation (Aβ) inhibitors as well as low cytotoxicity on healthy neuroblastoma SHSY5Y and hepatic THLE2 cells. Kinetic analysis and docking studies indicated hAChE dual site (mixed) inhibitory effect of compound 6h. Both compounds 6c and 6h complied with Lipinski's rule of five and were virtually able to cross the BBB. All the data suggested that compounds 6c and 6h have potential as a multifunctional therapy for AD.

Synthesis of 3-Aminoazaindazoles via Cu-Catalyzed Cross Coupling of Isocyanides

Nitrogen-containing heterocycles are commonly encountered in drug discovery, but the synthesis of such ring structures is not always efficient. Fused heterocyclic rings, in particular, can be challenging to synthesize. Herein, we report a highly convergent synthesis of 3-aminoazaindazoles via a Cu-catalyzed reaction between isocyanides and 3-halo-2-hydrazineylpyridines (and analogues). Reaction optimization through high-throughput experimentation (HTE) identified a novel set of exogenous ligand-free Cu conditions utilizing a cheap and readily available catalyst. The reaction displays high functional group tolerance and has the potential to be highly enabling for medicinal chemistry efforts. A putative mechanism is described as well as preliminary mechanistic experiments.

New 1,2,4-oxadiazole derivatives as potential multifunctional agents for the treatment of Alzheimer's disease: design, synthesis, and biological evaluation

A series of new 1,2,4-oxadiazole-based derivatives were synthesized and evaluated for their anti-AD potential. The results revealed that eleven compounds (1b, 2a-c, 3b, 4a-c, and 5a-c) exhibited excellent inhibitory potential against AChE, with IC50 values ranging from 0.00098 to 0.07920 µM. Their potency was 1.55 to 125.47 times higher than that of donepezil (IC50 = 0.12297 µM). In contrast, the newly synthesized oxadiazole derivatives with IC50 values in the range of 16.64-70.82 µM exhibited less selectivity towards BuChE when compared to rivastigmine (IC50 = 5.88 µM). Moreover, oxadiazole derivative 2c (IC50 = 463.85 µM) was more potent antioxidant than quercetin (IC50 = 491.23 µM). Compounds 3b (IC50 = 536.83 µM) and 3c (IC50 = 582.44 µM) exhibited comparable antioxidant activity to that of quercetin. Oxadiazole derivatives 3b (IC50 = 140.02 µM) and 4c (IC50 = 117.43 µM) showed prominent MAO-B inhibitory potential. They were more potent than biperiden (IC50 = 237.59 µM). Compounds 1a, 1b, 3a, 3c, and 4b exhibited remarkable MAO-A inhibitory potential, with IC50 values ranging from 47.25 to 129.7 µM. Their potency was 1.1 to 3.03 times higher than that of methylene blue (IC50 = 143.6 µM). Most of the synthesized oxadiazole derivatives provided significant protection against induced HRBCs lysis, revealing the nontoxic effect of the synthesized compounds, thus making them safe drug candidates. The results unveiled oxadiazole derivatives 2b, 2c, 3b, 4a, 4c, and 5a as multitarget anti-AD agents. The high AChE inhibitory potential can be computationally explained by the synthesized oxadiazole derivatives' significant interactions with the AChE active site. Compound 2b showed good physicochemical properties. All these data suggest that 2b could be considered as a promising candidate for future development.

Chemical exploration of different extracts from Phytolacca americana leaves and their potential utilization for global health problems: ın silico and network pharmacology validation

Phytolacca americana L. is of great interest as a traditional additive in various folk remedies in several countries, including Turkey. We aimed to determine the chemical profile (assisted by high-Performance liquid chromatography-electrospray ionization-tandem mass apectrometry (HPLC-ESI-MS/MS) experiments of three extracts obtained by different polarity solvents viz. ethyl acetate (to extract semipolar compounds), methanol and water (to extract highly polar metabolites) from P. americana leaves. Their anti-diabetic effects were investigated in vitro by assessing their inhibition toα-amylase and α-glucosidase. Assessment of the neuroprotective potential of the three extracts was carried out against acetyl-(AChE) and butyryl-(BChE) cholinesterase enzymes. HPLC-ESI-MS/MS experiments showed a total of 17 chromatographic peaks primarily classified to six flavonoids, two saponins, and six fatty acids. Antioxidant assays revealed remarkable activity for the ethyl acetate and methanol extracts. The BChE inhibition was considerably more significant (4.08 mg galantamine equivalent (GALAE)/g) for the ethyl acetate extract, whereas the methanol extract had good inhibitory efficacy for AChE (2.05 mg GALAE/g). Through network pharmacology, the compounds' mechanism of action of targeted key gene in their associated diseases were identified. The hubb gene signal transducer and activator of transcription 3 (STAT3) and tumour necrosis factor (TNFα) where the P. americana compound's site of action in inflammation bowel disease. The results offer possibilities for the prospective application of P. americana in metabolic regulation, blood glucose control, and as a source of bioactive compounds with cholinesterase enzyme inhibitory characteristics which could be of relevance in the cosmetic or pharmaceutical industry for combating melanogenesis.

Multi-targeted anti-Alzheimer's agents: Synthesis, biological evaluation, and molecular modeling study of some pyrazolopyridine hybrids

A new series of compounds bearing a pyrazolopyridine scaffold was synthesized as integrated anti-Alzheimer's disease (AD) multi-targeted ligands. Compounds 49 and 51 showed remarkable activity as hAChE inhibitors with IC50 values of 0.17 and 0.16 μM, respectively; and proved to be active hBuChE inhibitors with IC50 values 0.17 and 0.69 μM, eight and two-fold more active than the reference compound rivastigmine, respectively. Compounds 49 and 51 showed potent GSK3β inhibition with IC50 values of 0.21 and 0.26 μM, respectively compared to L807mts. Also, 49 and 51 showed 66.0 and 60.0% as tau protein aggregation inhibitors; and Aβ1-42 self-aggregation inhibitors with 79.0 and 75.0% respectively. Furthermore, 49 and 51 could bind virtually with the PAS affecting Aβ aggregation, thus preventing Aβ-dependent neurotoxicity. They proved to have the ability to chelate bio-metals such as Fe2+, Cu2+, and Zn2+ preventing their oxidative damage in the brain of AD patients, in addition to their safety upon WI-38 cell line. Both compounds could virtually penetrate BBB and obeyed Lipinski's rule of five. Compounds 49 and 51 could be considered as MTDLs for AD patients and the obtained model and pattern of substitution could be used for further development of new multi-targeted anti-Alzheimer's agents.

Synthesis of Highly Functionalized 4-Iodo-7-azaindazoles via Condensation/Diels-Alder/Retro-Diels-Alder Cyclization of Iodoalkynones and 2-Hydrazineylpyrimidines

A method for the preparation of highly functionalized 4-iodo-7-azaindazoles is reported. These valuable heterocycles are synthesized via condensation of 2-hydrazineylpyrimidines with various iodoalkynones followed by Diels-Alder/retro-Diels-Alder cyclization. The method is general to the formation of products with a variety of C3, C5, and C6 substituents while preserving the C4 iodide functional handle for further late-stage functionalization. The utility of this transformation is demonstrated through the rapid synthesis of several bioactive azaindazole targets.

Design, synthesis and biological evaluation of novel indanones derivatives as potent acetylcholinesterase/monoamine oxidase B inhibitors

Aim: Based on a multitarget design strategy, a series of novel indanone-1-benzyl-1,2,3,6-tetrahydropyridin hybrids were identified for the potential treatment of Alzheimer's disease (AD). Results: These compounds exhibited significant inhibitory activities against acetylcholinesterase (AChE) and moderate inhibitory activities toward monoamine oxidase B (MAO-B). The optimal compound A1 possessed excellent dual AChE/MAO-B inhibition both in terms of potency (AChE: IC50 = 0.054 ± 0.004 μM; MAO-B: IC50 = 3.25 ± 0.20 μM), moderate inhibitory effects on self-mediated amyloid-β (Aβ) aggregation and antioxidant activity. In addition, compound A1 exhibited low neurotoxicity. More importantly, compound A1 showed significant cognitive and spatial memory improvements in the scopolamine-induced AD mouse model. Conclusion: All results suggest that compound A1 may become a promising lead of anti-AD drug for further development.

Microwave assisted one-pot access to pyrazolo quinolinone and tetrahydroisoxazolo quinolinone derivatives via T3P®-DMSO catalysed tandem oxidative-condensation reaction

A new approach for the synthesis of two important annulated pyrazolo quinolinone and tetrahydroisoxazolo quinolinone derivatives from multicomponent reactions was achieved by using T3P®-DMSO-catalysed reactions of stable alcohols, cyclic 1,3-dicarbonyl compounds and amino derivatives of phenyl pyrazoles and isoxazole and has been reported for the first time. This reaction occurred via a tandem oxidative-condensation reaction under microwave irradiation and notable characteristics of this protocol are MCR reactions, shorter reaction time, less waste creation, ease of workup, stable precursors, broad substrate scope and functional group tolerance.

Modified Tacrine Derivatives as Multitarget-Directed Ligands for the Treatment of Alzheimer's Disease: Synthesis, Biological Evaluation, and Molecular Modeling Study

To develop multitarget-directed ligands (MTDLs) as potential treatments for Alzheimer's disease (AD) and to shed light on the effect of the chromene group in designing these ligands, 35 new tacrine-chromene derivatives were designed, synthesized, and biologically evaluated. Compounds 5c and 5d exhibited the most desirable multiple functions for AD; they were strong hAChE inhibitors with IC₅₀ values of 0.44 and 0.25 μM, respectively. Besides, their potent BuChE inhibitory activity was 10- and 5-fold more active than rivastigmine with IC₅₀ = 0.08 and 0.14 μM, respectively. Moreover, they could bind to the peripheral anionic site (PAS), influencing Aβ aggregation and decreasing Aβ-related neurodegeneration, especially compound 5d, which was 8 times more effective than curcumin with IC₅₀ = 0.74 μM and 76% inhibition at 10 μM. Compounds 5c and 5d showed strong BACE-1 inhibition at the submicromolar level with IC₅₀ = 0.38 and 0.44 μM, respectively, which almost doubled the activity of curcumin. They also showed single-digit micromolar inhibitory activity against MAO-B with IC₅₀ = 5.15 and 2.42 μM, respectively. They also had antioxidant activities and showed satisfactory metal-chelating properties toward Fe⁺², Zn⁺², and Cu⁺², inhibiting oxidative stress in AD brains. Furthermore, compounds 5c and 5d showed acceptable relative safety upon normal cells SH-SY5Y and HepG2. It was shown that 5c and 5d were blood-brain barrier (BBB) penetrants by online prediction. Taken together, these multifunctional properties highlight that compounds 5c and 5d can serve as promising candidates for the further development of multifunctional drugs against AD.

Multicomponent Petasis reaction for the identification of pyrazine based multi-target directed anti-Alzheimer's agents: In-silico design, synthesis, and characterization

Multi-target directed ligands (MTDLs) have recently attracted significant interest due to their exceptional effectiveness against multi-factorial Alzheimer's disease. The present work described the development of pyrazine-based MTDLs using multicomponent Petasis reaction for the dual inhibition of tau-aggregation and human acetylcholinesterase (hAChE). The molecular structure of synthesized ligands was validated by ¹H & ¹³C NMR and mass spectrometry. The screened compounds were shown to have a strong inhibitory effect at 10 μM concentration against tau-oligomerization and hAChE, but only moderate inhibitory activity against Aβ₄₂. Among all the compounds, the half-maximal inhibitory concentration (IC₅₀) for 21 and 24 against hAChE were 0.71 μM and 1.09 μM, respectively, while they displayed half-maximal effective concentrations (EC₅₀) values of 2.21 μM and 2.71 μM for cellular tau-oligomerization, respectively. Additionally, an MTT experiment using tau-expressing SH-SY5Y neuroblastoma cells revealed that 21 was more neuroprotective than the FDA-approved medication donepezil. Furthermore, an MD simulation study was performed to investigate the dynamics and stability of AChE-21 and AChE-24 complexes in an aqueous environment. The MM-PBSA calculations were performed to evaluate the binding of 21 and 24 with AChE, and the relative binding energy was calculated as -870.578 and -875.697 kJ mol^-1, respectively. As a result, the study offered insight into the design of new MTDLs and highlighted 21 as a potential roadblock to the development of anti-AD medications.

Identification of new oxospiro chromane quinoline-carboxylate antimalarials that arrest parasite growth at ring stage

Malaria still threatens half the globe population despite successful Artemisinin-based combination therapy. One of the reasons for our inability to eradicate malaria is the emergence of resistance to current antimalarials. Thus, there is a need to develop new antimalarials targeting Plasmodium proteins. The present study reported the design and synthesis of 4, 6 and 7-substituted quinoline-3-carboxylates 9(a-o) and carboxylic acids 10(a-b) for the inhibition of Plasmodium N-Myristoyltransferases (NMTs) using computational biology tools followed by chemical synthesis and functional analysis. The designed compounds exhibited a glide score of -9.241 to -6.960 kcal/mol for PvNMT and -7.538 kcal/mol for PfNMT model proteins. Development of the synthesized compounds was established via NMR, HRMS and single crystal X-ray diffraction study. The synthesized compounds were evaluated for their in vitro antimalarial efficacy against CQ-sensitive Pf3D7 and CQ-resistant PfINDO lines followed by cell toxicity evaluation. In silico results highlighted the compound ethyl 6-methyl-4-(naphthalen-2-yloxy)quinoline-3-carboxylate (9a) as a promising inhibitor with a glide score of -9.084 kcal/mol for PvNMT and -6.975 kcal/mol for PfNMT with IC50 values of 6.58 µM for Pf3D7 line. Furthermore, compounds 9n and 9o exhibited excellent anti-plasmodial activity (Pf3D7 IC50 = 3.96, 6.71 µM, and PfINDO IC50 = 6.38, 2.8 µM, respectively). The conformational stability of 9a with the active site of the target protein was analyzed through MD simulation and was found concordance with in vitro results. Thus, our study provides scaffolds for the development of potent antimalarials targeting both Plasmodium vivax and Plasmodium falciparum.Communicated by Ramaswamy H. Sarma.

Anticancer evaluation and molecular docking of new pyridopyrazolo-triazine and pyridopyrazolo-triazole derivatives

3-Amino-4,6-dimethylpyrazolopyridine was applied as a precursor for the synthesis of some new pyridopyrazolo-triazine and pyridopyrazolo-triazole derivatives through diazotization, followed by coupling with many 2-cyanoacetamide compounds, ethyl 3-(phenylamino)-3-thioxopropanoate, 3-oxo-N-phenylbutanethioamide, and α-bromo-ketone reagents [namely; 2-bromo-1-(4-fluorophenyl)ethan-1-one, 5-bromo-2-(bromoacetyl)thiophene, 3-(2-bromoacetyl)-2H-chromen-2-one and/or 3-chloroacetylacetone]. The prepared compounds were identified by spectroscopic analyses as IR, ¹H NMR, and mass data. The anticancer activity of these pyrazolopyridine analogues was investigated in colon, hepatocellular, breast, and cervix carcinoma cell lines. The pyridopyrazolo-triazine compound 5a substituted with a carboxylate group gave a distinguished value of IC₅₀ = 3.89 µM against the MCF-7 cell line compared to doxorubicin as a reference drug. Also, the pyridopyrazolo-triazine compound 6a substituted with the carbothioamide function gave good activity toward HCT-116 and MCF-7 cell lines with IC₅₀ values of 12.58 and 11.71 µM, respectively. The discovered pyrazolopyridine derivatives were studied theoretically by molecular docking, and this study exhibited suitable binding between the active sides of pyrazolopyridine ligands and proteins (PDB ID: 5IVE). The pyridopyrazolo-triazine compound 6a showed the highest free binding energy (- 7.8182 kcal/mol) when docked inside the active site of selected proteins.

Design, Synthesis and Pharmacological Evaluation of New Quinoline-Based Panx-1 Channel Blockers

Pannexins are an interesting new target in medicinal chemistry, as they are involved in many pathologies such as epilepsy, ischemic stroke, cancer and Parkinson's disease, as well as in neuropathic pain. They are a family of membrane channel proteins consisting of three members, Panx-1, Panx-2 and Panx-3, and are expressed in vertebrates. In the present study, as a continuation of our research in this field, we report the design, synthesis and pharmacological evaluation of new quinoline-based Panx-1 blockers. The most relevant compounds 6f and 6g show an IC₅₀ = 3 and 1.5 µM, respectively, and are selective Panx-1 blockers. Finally, chemical stability, molecular modelling and X-ray crystallography studies have been performed providing useful information for the realization of the project.

Understanding Alzheimer's Disease and its Metal Chelation Therapeutics: A Narrative Review

The neurodegenerative disorders are age-related illnesses that cause the morphology or activity of neurons to deteriorate over time. Alzheimer's disease is the most frequent neurodegenerative illness in the long run. The rate of advancement might vary, even though it is a progressive neurological illness. Various explanations have been proposed, however the true etiology of Alzheimer's disease remains unclear. Most pharmacological interventions are based on the cholinergic theory, that is earliest idea. In accordance with the amyloid hypothesis, the buildup of beta-amyloid in brain regions is the primitive cause of illness. There is no proof that any one strategy is useful in avoiding Alzheimer's disease, though some epidemiological studies have suggested links within various modifiable variables, such as cardiovascular risk, diet and so on. Different metals like zinc, iron, and copper are naturally present in our bodies. In metal chelation therapy drugs are used to jam the metal ions from combining with other molecules in the body. Clioquinol is one of the metal chelation drugs used by researchers. Research on metal chelation is still ongoing. In the present review, we go over the latest developments in prevalence, incidence, etiology, or pathophysiology of our understanding of Alzheimer's disease. Additionally, a brief discussion on the development of therapeutic chelating agents and their viability as Alzheimer's disease medication candidates is presented. We also assess the effect of clioquinol as a potential metal chelator.

Design, synthesis, theoretical study, antioxidant, and anticholinesterase activities of new pyrazolo-fused phenanthrolines

Pyrazole-fused phenanthroline compounds were obtained through several synthetic routes. NMR, HRMS, and IR techniques were used to characterize and confirm the chemical structures. Crystal structures were obtained from compounds 3a, 5b, 5j, 5k, and 5n and analyzed using X-ray diffraction. Compounds were evaluated as acetyl (AChE) and butyrylcholinesterase (BChE) inhibitors, and the results showed a moderate activity. Compound 5c presented the best activity against AChE (IC50 = 53.29 μM) and compound 5l against BChE enzyme (IC50 = 119.3 μM). Furthermore, the ability of the synthetic compounds to scavenge cationic radicals DPPH and ABTS was evaluated. Compound 5e (EC50 = 26.71 μg mL-1) presented the best results in the DPPH assay, and compounds 5e, 5f and 5g (EC50 = 11.51, 3.10 and <3 μg mL-1, respectively) showed better ABTS cationic radical scavenging results. Finally, in silico analyses indicated that 71% of the compounds show good oral availability and are within the ranges established by the Lipinski criteria.

Toward the cholinesterase inhibition potential of TADDOL derivatives: Seminal biological and computational studies

Alzheimer's disease (AD) is a degenerative neurological disease characterized by gradual loss of cognitive skills and memory. The exact pathogenesis involved still remains unrevealed, but several studies indicate the involvement of an array of different enzymes, underlining the multifactorial character of the disease. Inhibition of these enzymes is therefore a powerful approach in the development of AD treatments, with promising candidates, including acetylcholinesterase (AChE), butyrylcholinesterase (BuChE), and monoamine oxidase. Interestingly, AChE is the target of a major pesticide family (organophosphates), with several reports indicating an intersection between the pesticide's activity and AD. In this study, various TADDOL derivatives were synthesized and their in vitro activities as AChE/BuChE inhibitors as well as their antioxidant activities were studied. Molecular modeling studies revealed the capability of TADDOL derivatives to bind to AChE and induce inhibition, especially compounds 2b and 3c furnishing IC50 values of 36.78 ± 8.97 and 59.23 ± 5.31 µM, respectively. Experimental biological activities and molecular modeling studies clearly demonstrate that TADDOL derivatives with specific stereochemistry have an interesting potential for the design of potent AChE inhibitors. The encouraging results for compounds 2b and 3c indicate them as promising scaffolds for selective and potent AChE inhibitors.

High-Pressure Metal-Free Catalyzed One-Pot Two-Component Synthetic Approach for New 5-Arylazopyrazolo[3,4-b]Pyridine Derivatives

An appropriate and efficient Q-tube-assisted ammonium acetate-mediated protocol for the assembly of the hitherto unreported 5-arylazopyrazolo[3,4-b]pyridines was demonstrated. This methodology comprises the cyclocondensation reaction of 5-amino-2-phenyl-4H-pyrazol-3-one with an assortment of arylhydrazonals in an NH4OAc/AcOH buffer solution operating a Q-tube reactor. This versatile protocol exhibited several outstanding merits: easy work-up, mild conditions, scalability, broad substrate scope, safety (the Q-tube kit is simply for pressing and sealing), and a high atom economy. Consequently, performing such reactions under elevated pressures and utilizing the Q-tube reactor seemed preferable for achieving the required products in comparison to the conventional conditions. Diverse spectroscopic methods and X-ray single-crystal techniques were applied to confirm the proposed structure of the targeted compounds.

Recent Updates in Development of Small Molecules as Potential Clinical Candidates for Alzheimer's Disease: A Review

Alzheimer's disease (AD) is one of the prominent causes for disability and lowered quality of life worldwide in elderly population. It has fostered immense burden to AD patients, families and society. Burgeoning progress in the field of pathogenesis over last two decades has persuaded the investigation of novel pharmacological therapeutics that focuses towards the pathophysiological events of AD. Miscellaneous clinical trials, development and testing of interventions aimed at various targets, such as anti-tau and anti-amyloid interventions, neurotransmitter modification, neuroprotection and anti-neuroinflammation interventions, cognitive enhancement, and interventions to palliate behavioral symptoms have been carried out. Despite massive efforts to find disease modifying therapies there lingers a vital need for continuing the advancement in progress of the AD research. This review features the new developments of small molecule compounds that will be beneficial in evolution of new AD therapies. In particular, this review briefly describes summary of mechanistic causes chiefly associated with AD and focuses on medicinal approach via small molecule inhibitors that can manage cognitive impairment and dysfunction and may combat Alzheimer's development.

Synthesis, anticholinesterase activity, molecular docking, and molecular dynamic simulation studies of 1,3,4-oxadiazole derivatives

Two new series of 1,3,4-oxadiazoles bearing pyridine and thiazole heterocycles (4a-h and 5a-h) were synthesized (2,5-disubstituted-1,3,4-oxadiazoles). The structures of these newly synthesized compounds were confirmed by ¹ H nuclear magnetic resonance (NMR), ¹³ C NMR, high-resolution mass spectrometric and Fourier transform infrared spectroscopic methods. All these compounds were evaluated for their enzyme inhibitory activities against two cholinesterase enzymes, acetylcholinesterase (AChE) and butyrylcholinesterase (BChE). From the studies, we identified compounds 4a, 4h, 5a, 5d, and 5e as selective AChE inhibitors, with IC₅₀ values ranging from 0.023 to 0.037 μM. Furthermore, docking studies of these compounds were performed at the active sites of their target enzymes. The molecular docking study showed that 5e possessed an ideal docking pose with interactions inside AChE.

Pyrazolopyridine: An efficient pharmacophore in recent drug design and development

Among the various heterocyclic molecules employed for drug design and discovery, pyrazolopyridine is one of the promising pharmacophores. Pyrazolopyridine is a result of fusion of pyrazole and pyridine rings. The potent pharmacology of pyrazolopyridine may be the synergistic effect of pyrazole and pyridine moieties in a single framework. It has been used in drug design of a wide range of diseases such as anticancer, antimicrobial, anti-inflammatory, and neuroprotection. Cancer has become a common disease among elderly people now a days that might be because of genetic inheritance to some extent, carcinogens, pollution, and some infectious diseases. Whatever may be the reason, cancer is one of the major causes of deaths worldwide. In addition, over-usage and improper usage of antibiotics have led to drug resistance of microbes. Further, inflammation is a cause of various diseases such as arthritis, and other diseases. Thus, proinflammatory kinases are considered as primary target for inhibition of inflammation. In view of this, a work that compiles potent pharmacology of recently reported pyrazolopyridine analogs has been planned. The review is aimed to discuss pharmacology in brief along with structure-activity relationship (SAR). The review would emphasize importance of pyrazolopyridines in future drug design and discovery and may help in design of potent pharmacological agents.

Promising heterocycle-based scaffolds in recent (2019-2021) anti-Alzheimer's drug design and discovery

Alzheimer's disease (AD) is one of the neurodegenerative diseases that led to morbidity and mortality world-wide. It is a complex disease whose etiology is not completely known that leads to difficulty in prevent or cure of the AD. Also, there are only few approved drugs for AD treatment. Apart from deaths due to AD, expenditure of treatment and care of AD patients is higher than that of treatment of HIV and cancer diseases combined. Hence, it leads to an economic burden also. Although research is being carried out on designing drugs for AD, most of them have ended up in poor inhibitors with high toxicity. Hence, researchers should shoulder a great responsibility of discovery of efficient drugs for AD treatment. In the field of drug discovery, heterocycles played an important role. Also, most of the heterocyclic scaffolds have been used in design of potent anti-AD agents. In view of this, heterocyclic molecules reported recently are compiled and evaluated comprehensively. Especially, the molecules which exhibited pronounced activity are emphasized and described with respect to structure-activity relationship (SAR) in brief.

An Expedient Approach to Pyrazolo[3,4-b]pyridine-3-carboxamides via Palladium-Catalyzed Aminocarbonylation

Pyrazolo[3,4-b]pyridine is a privileged scaffold found in many small drug molecules that possess a wide range of pharmacological properties. Efforts to further develop and exploit synthetic methodologies that permit the functionalization of this heterocyclic moiety warrant investigation. To this end, a series of novel 1,3-disubstituted pyrazolo[3,4-b]pyridine-3-carboxamide derivatives have been prepared by introducing the 3-carboxamide moiety using palladium-catalyzed aminocarbonylation methodology and employing CO gas generated ex situ using a two-chamber reactor (COware®). The functional group tolerance of this optimized aminocarbonylation protocol is highlighted through the synthesis of a range of diversely substituted C-3 carbox­amide pyrazolo[3,4-b]pyridines in excellent yields of up to 99%.

One-pot three-component synthesis of novel pyrazolo[3,4-b]pyridines as potent antileukemic agents

In the current study, we report on the development of novel series of pyrazolo[3,4-b]pyridine derivatives (8a-u, 11a-n, and 14a,b) as potential anticancer agents. The prepared pyrazolo[3,4-b]pyridines have been screened for their antitumor activity in vitro at NCI-DTP. Thereafter, compound 8a was qualified by NCI for full panel five-dose assay to assess its GI₅₀, TGI and LC₅₀ values. Compound 8a showed broad-spectrum anti-proliferative activities over the whole NCI panel, with outstanding growth inhibition full panel GI₅₀ (MG-MID) value equals 2.16 μM and subpanel GI₅₀ (MG-MID) range: 1.92-2.86 μM. Furthermore, pyrazolo[3,4-b]pyridines 8a, 8e-h, 8o, 8u, 11a, 11e, 11h, 11l and 14a-b were assayed for their antiproliferative effect against a panel of leukemia cell lines (K562, MV4-11, CEM, RS4;11, ML-2 and KOPN-8) where they possessed moderate to excellent anti-leukemic activity. Moreover, pyrazolo[3,4-b]pyridines 8o, 8u, 14a and 14b were further explored for their effect on cell cycle on RS4;11 cells, in which they dose-dependently increased populations of cells in G2/M phases. Finally we analyzed the changes of selected proteins (HOXA9, MEIS1, PARP, BcL-2 and McL-1) related to cell death and viability in RS4;11 cells via Western blotting. Collectively, the obtained results suggested pyrazolo[3,4-b]pyridines 8o, 8u, 14a and 14b as promising lead molecules for further optimization to develop more potent and efficient anticancer candidates.

In-vitro evaluation of antioxidant and anticholinesterase activities of novel pyridine, quinoxaline and s-triazine derivatives

Cholinesterase enzymes such as acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) cause hydrolysis of acetylcholine (ACh), a neurotransmitter responsible for the cognitive functions of the brain such as acquiring knowledge and comprehension. Therefore, inhibition of these enzymes is an effective process to curb the progressive and fatal neurological Alzheimer's disease (AD). Herein, we explored the potential inhibitory activities of various pyridine, quinoxaline, and triazine derivatives (3a-k, 6a-j and 11a-h) against AChE and BuChE enzymes by following the modified Ellman's method. Further, anti-oxidant property of these libraries was monitored using DPPH (2,2'-diphenyl-1-picryl-hydrazylhydrate) radical scavenging analysis. From the studies, we identified that compounds 6e, 6f, 11b and 11f behaved as selective AChE inhibitors with IC₅₀ values ranging from 7.23 to 10.35 μM. Further studies revealed good anti-oxidant activity by these compounds with IC₅₀ values in the range of 14.80-27.22 μM. The kinetic studies of the active analogues demonstrated mixed-type of inhibition due to their interaction with both the catalytic active sites (CAS) and peripheral anionic sites (PAS) of the AChE. Additionally, molecular simulation in association with fluorescence and circular dichroism (CD) spectroscopic analyses explained strong affinities of inhibitors to bind with AChE enzyme at the physiological pH of 7.2. Binding constant values of 5.4 × 10⁴, 4.3 × 10⁴, 3.2 × 10⁴ and 4.9 × 10⁴ M^-1 corresponding to free energy changes -5.593, -6.799, -6.605 and -8.104 KcalM^-1 were obtained at 25 °C from fluorescence emission spectroscopic studies of 6e, 6f, 11b and 11f, respectively. Besides, CD spectroscopy deliberately explained the secondary structure of AChE partly unfolded upon binding with these dynamic molecules. Excellent in vitro profiles of distinct quinoxaline and triazine compounds highlighted them as the potential leads compared to pyridine derivatives, suggesting a path towards developing preventive or therapeutic targets to treat the Alzheimer's disease.

Discovery of 7-O-1, 2, 3-triazole hesperetin derivatives as multi-target-directed ligands against Alzheimer's disease

The development of multi-target-directed ligands (MTDLs) may improve complex central nervous system diseases such as Alzheimer's disease (AD). Here, a series of 7-O-1, 2, 3-triazole hesperetin derivatives was evaluated for their inhibition of cholinesterase, anti-neuroinflammatory, and neuroprotective activity. Among the hesperetin derivatives, compound a8 (7-O-((1-(3-chlorobenzyl)-1H-1,2,3-triazol-4-yl)methyl)hesperetin) possessed excellent anti-butyrylcholinesterase activity (IC50 = 3.08 ± 0.29 μM) and exhibited good anti-neuroinflammatory activity (IC50 = 2.91 ± 0.47 μM) against NO production through remarkably blocking the NF-κB signaling pathway and inhibiting the phosphorylation of P65. In addition, a8 showed a remarkable neuroprotective effect and lacked neurotoxicity up to 50 μM concentration. Furthermore, possessing significant self-mediated Aβ1-42 aggregation inhibitory activity, chelated biometals and reduced ROS production were found in compound a8. In the bi-directional transport assay, a8 exhibited a blood-brain barrier penetrating ability. In this study, the Morris water maze task showed that compound a8 significantly improved the learning and memory impairment of the scopolamine-induced AD mice model. Results highlighted the potential of compound a8 to be a potential MTDL for the development of anti-AD agents.

Deciphering the robustness of pyrazolo-pyridine carboxylate core structure-based compounds for inhibiting α-synuclein in transgenic C. elegans model of Synucleinopathy

Parkinson's disease (PD), a calamitous neurodegenerative disorder with no cure till date, is closely allied with the misfolding and aggregation of α-Synuclein (α -Syn). Inhibition of α-Syn aggregation is one of the optimistic approaches for the treatment for PD. Here, we carried out hypothesis-driven studies towards synthesising a series of pyrazolo-pyridine carboxylate containing compounds (7a-7m) targeted at reducing deleterious α-Syn aggregation. The target compounds were synthesized through multi-step organic synthesis reactions. From docking studies, compounds 7b, 7g and 7i displayed better interaction with the key residues of α-Syn with values: -6.8, -8.9 and -7.2 Kcal/mol, respectively. In vivo transgenic C. elegans model of Synucleinopathy was used to evaluate the ability of the designed and synthesized compounds to inhibit α-Syn aggregation. These lead compounds 7b, 7g and 7i displayed 1.7, 2.4 and 1.5-fold inhibition of α-Syn with respect to the control. Further, the strategy of employing pyrazolo-pyridine-based compounds worked with success and these scaffolds could be further modified and validated for betterment of endpoints associated with PD.

Structural and biological survey of 7-chloro-4-(piperazin-1-yl)quinoline and its derivatives

The 7-chloro-4-(piperazin-1-yl)quinoline structure is an important scaffold in medicinal chemistry. It exhibited either alone or as hybrid with other active pharmacophores diverse pharmacological profiles such as: antimalarial, antiparasitic, anti-HIV, antidiabetic, anticancer, sirtuin Inhibitors, dopamine-3 ligands, acetylcholinesterase inhibitors, and serotonin antagonists. In the presented review, a comprehensive discussion of compounds having this structural core is surveyed and illustrated.

Synthesis, pharmacological evaluation and structure-activity relationship of recently discovered enzyme antagonist azoles

Global people are suffering from the legion of diseases. Cytotoxic property of the chemical compound would not solely influence effective drug properties and reduce unnecessary side effects. Proteins/enzymes responsible for microbe proliferation or survival are specifically targeted and inhibited successfully making the cells to undergo apoptosis. Furthermore, isoforms of essential enzymes have distinct physiological functions; thereby inhibition of essential enzyme isoforms is an apt way to the clinical approach of disease neutralization. Drugs are designed so as to play significant roles such as signaling pathways in the oncogenic process including cell proliferation, invasion, and angiogenesis. The present review comprises collective information of the recent synthesis of various organic drug compounds in brief, which could inhibit particular enzyme. The review also covers the correlation of the structure of a drug molecule designed and its inhibitory activity. Also, the most significant enzyme inhibitors are highlighted and structural moieties/core units responsible for remarkable inhibitory values are emphasized.

A one-pot three-component strategy for highly diastereoselective synthesis of spirocycloalkane fused pyrazolo[3,4-b]pyridine derivatives using recyclable solid acid as a catalyst

An efficient and eco-friendly approach for highly diastereoselective synthesis of spirocycloalkane fused pyrazolo[3,4-b]pyridine derivatives has been developed.

Development of novel N-(6-methanesulfonyl-benzothiazol-2-yl)-3-(4-substituted-piperazin-1-yl)-propionamides with cholinesterase inhibition, anti-β-amyloid aggregation, neuroprotection and cognition enhancing properties for the therapy of Alzheimer's disease

A novel series of benzothiazole–piperazine hybrids were rationally designed, synthesized, and evaluated as multifunctional ligands against Alzheimer's disease (AD). The synthesized hybrid molecules illustrated modest to strong inhibition of acetylcholinesterase (AChE) and Aβ_1-42 aggregation. Compound 12 emerged as the most potent hybrid molecule exhibiting balanced functions with effective, uncompetitive and selective inhibition against AChE (IC₅₀ = 2.31 μM), good copper chelation, Aβ_1-42 aggregation inhibition (53.30%) and disaggregation activities. Confocal laser scanning microscopy and TEM analysis also validate the Aβ fibril inhibition ability of this compound. Furthermore, this compound has also shown low toxicity and is capable of impeding loss of cell viability elicited by H₂O₂ neurotoxicity in SHSY-5Y cells. Notably, compound 12 significantly improved cognition and spatial memory against scopolamine-induced memory deficit in a mouse model. Hence, our results corroborate the multifunctional nature of novel hybrid molecule 12 against AD and it may be a suitable lead for further development as an effective therapeutic agent for therapy in the future.

A novel series of benzothiazole–piperazine hybrids were rationally designed, synthesized, and evaluated as multifunctional ligands against Alzheimer's disease (AD).

A multicomponent, facile and catalyst-free microwave-assisted protocol for the synthesis of pyrazolo-[3,4-b]-quinolines under green conditions

A facile, swift and ecofriendly microwave-assisted multi-component/one-pot protocol is designed for the synthesis of novel pyrazolo-[3,4-b]-quinolines at ambient temperature in aqueous ethanol as a reaction medium. The 18 novel pyrazolo-[3,4-b]-quinoline derivatives were synthesized by fusion of chosen aryl aldehyde, dimedone and 5-amino-3-methyl-1-phenylpyrazole in excellent yields (91–98%). All the molecular structures were confirmed by ¹H-NMR, ¹⁵N-NMR, ¹³C-NMR, and HRMS data analysis. Operational simplicity, easy handling, one-step simple workup procedure, mild reaction conditions, short reaction time (≤10 min), high selectivity and no by-product formation are the striking features of the protocol.

A facile, swift and ecofriendly microwave-assisted multi-component/one-pot protocol is designed for the synthesis of novel pyrazolo-[3,4-b]-quinolines at ambient temperature in aqueous ethanol as a reaction medium.