5,6-Diphenyl triazine-thio methyl triazole hybrid as a new Alzheimer's disease modifying agents

Synthesis of novel aryl-substituted 2-aminopyridine derivatives by the cascade reaction of 1,1-enediamines with vinamidinium salts to develop novel anti-Alzheimer agents

Alzheimer's disease (AD), a severe neurodegenerative disorder, imposes socioeconomic burdens and necessitates innovative therapeutic strategies. Current therapeutic interventions are limited and underscore the need for novel inhibitors of acetylcholinesterase (AChE) and butyrylcholinesterase (BChE), enzymes implicated in the pathogenesis of AD. In this study, we report a novel synthetic strategy for the generation of 2-aminopyridine derivatives via a two-component reaction converging aryl vinamidinium salts with 1,1-enediamines (EDAMs) in a dimethyl sulfoxide (DMSO) solvent system, catalyzed by triethylamine (Et3N). The protocol introduces a rapid, efficient, and scalable synthetic pathway, achieving good to excellent yields while maintaining simplistic workup procedures. Seventeen derivatives were synthesized and subsequently screened for their inhibitory activity against AChE and BChE. The most potent derivative, 3m, exhibited an IC50 value of 34.81 ± 3.71 µM against AChE and 20.66 ± 1.01 µM against BChE compared to positive control donepezil with an IC50 value of 0.079 ± 0.05 µM against AChE and 10.6 ± 2.1 µM against BChE. Also, detailed kinetic studies were undertaken to elucidate their modes of enzymatic inhibition of the most potent compounds against both AChE and BChE. The promising compound was then subjected to molecular docking and dynamics simulations, revealing significant binding affinities and favorable interaction profiles against AChE and BChE. The in silico ADMET assessments further determined the drug-like properties of 3m, suggesting it as a promising candidate for further pre-clinical development.

Pathogenesis of Alzheimer's Disease and Diversity of 1,2,3-Triazole Scaffold in Drug Development: Design Strategies, Structural Insights, and Therapeutic Potential

Alzheimer's disease is a most prevalent form of dementia all around the globe and currently poses a significant challenge to the healthcare system. Currently available drugs only slow the progression of this disease rather than provide proper containment. Identification of multiple targets responsible for this disease in the last three decades established it as a multifactorial neurodegenerative disorder that needs novel multifunctional agents for its management and the possible reason for the failure of currently available single target clinical drugs. 1,2,3-Triazole is a miraculous nucleus in medicinal chemistry and the first choice for development of multifunctional hybrid molecules. Apart from that, it is an integral component of various drugs in clinical trials as well as in clinical practice. This review is focused on the pathogenesis of Alzheimer's disease and 1,2,3-triazole containing derivatives developed in recent decades as potential anti-Alzheimer's agents. The review will provide (A) precise insight of various established targets of Alzheimer's disease including cholinergic, amyloid, tau, monoamine oxidases, glutamate, calcium, and reactive oxygen species hypothesis and (B) design hypothesis, structure-activity relationships, and pharmacological outcomes of 1,2,3-triazole containing multifunctional anti-Alzheimer's agents. This review will provide a baseline for various research groups working on Alzheimer's drug development in designing potent, safer, and effective multifunctional anti-Alzheimer's candidates of the future.

Design, Synthesis, and Pharmacological Evaluation of Embelin-Aryl/alkyl Amine Hybrids as Orally Bioavailable Blood-Brain Barrier Permeable Multitargeted Agents with Therapeutic Potential in Alzheimer's Disease: Discovery of SB-1448

The complex and multifaceted nature of Alzheimer's disease has brought about a pressing demand to develop ligands targeting multiple pathways to combat its outrageous prevalence. Embelin is a major secondary metabolite of Embelia ribes Burm f., one of the oldest herbs in Indian traditional medicine. It is a micromolar inhibitor of cholinesterases (ChEs) and β-site amyloid precursor protein cleaving enzyme 1 (BACE-1) with poor absorption, distribution, metabolism, and excretion (ADME) properties. Herein, we synthesize a series of embelin-aryl/alkyl amine hybrids to improve its physicochemical properties and therapeutic potency against targeted enzymes. The most active derivative, 9j (SB-1448), inhibits human acetylcholinesterase (hAChE), human butyrylcholinesterase (hBChE), and human BACE-1 (hBACE-1) with IC₅₀ values of 0.15, 1.6, and 0.6 μM, respectively. It inhibits both ChEs noncompetitively with k_i values of 0.21 and 1.3 μM, respectively. It is orally bioavailable, crosses blood-brain barrier (BBB), inhibits Aβ self-aggregation, possesses good ADME properties, and protects neuronal cells from scopolamine-induced cell death. The oral administration of 9j at 30 mg/kg attenuates the scopolamine-induced cognitive impairments in C57BL/6J mice.

Multiple roles of fucoxanthin and astaxanthin against Alzheimer's disease: Their pharmacological potential and therapeutic insights

Alzheimer's disease (AD) is the most devastating neurodegenerative disorder affecting the elderly. The exact pathology of AD is not yet fully understood and several hallmarks such as the deposition of amyloid-β, tau hyperphosphorylation, and neuroinflammation, as well as mitochondrial, metal ions, autophagy, and cholinergic dysfunctions are known as pathologic features of AD. Since no definitive treatment has been proposed to target AD to date, many natural products have shown promising preventive potentials and contributed to slowing down the disease progression. Algae is a promising source of novel bioactive substances known to prevent neurodegenerative disorders including AD. In this context, fucoxanthin and astaxanthin, natural carotenoids abundant in algae, has shown to possess neuroprotective properties through antioxidant, and anti-inflammatory characteristics in modulating the symptoms of AD. Fucoxanthin and astaxanthin exhibit anti-AD activities by inhibition of AChE, BuChE, BACE-1, and MAO, suppression of Aβ accumulation. Also, fucoxanthin and astaxanthin inhibit apoptosis induced by Aβ_1-42 and H₂O₂-induced cytotoxicity, and modulate the antioxidant enzymes (SOD and CAT), through inhibition of the ERK pathway. Moreover, cellular and animal studies on the beneficial effects of fucoxanthin and astaxanthin against AD were also reviewed. The potential role of fucoxanthin and astaxanthin exhibits great efficacy for the management of AD by acting on multiple targets.

Design, synthesis, in silico and biological evaluations of novel polysubstituted pyrroles as selective acetylcholinesterase inhibitors against Alzheimer's disease

The objective of this study was to design new polysubstituted pyrrole derivatives as selective acetylcholinesterase (AChE) inhibitors to target Alzheimer's disease. In this context, a highly efficient, one-pot, sequential, multi-component synthesis of a diverse range of polysubstituted pyrroles was developed through a sequential domino strategy by the condensation of amines with 1,1-bis(methylthio)-2-nitroethene (BMTNE), Knovenagle reaction of arylglyoxals with malono derivatives and subsequent Michael addition and intramolecular cyclization reaction in EtOH at reflux. Thirty-nine synthesized compounds were evaluated as AChE and butyrylcholinesterase (BChE) inhibitors. Among the synthesized compounds, compound 4ad (IC₅₀ = 2.95 ± 1.31 µM) was the most potent and selective AChE inhibitor with no significant inhibition against butyrylcholinesterase BChE. A kinetic study of 4ad revealed that this compound inhibited AChE in an uncompetitive mode. Based on a molecular modeling study, compound 4ad due to its small size properly fitted into the active site of AChE compared to BChE and stabilized by H-bond and hydrophobic interactions with the critical residues of the AChE binding pocket. Consequently, it was proposed that the 4ad derivative can be an ideal lead candidate against AD with a simple and practical operation of synthetic procedures.

Design, synthesis, and molecular docking studies of diphenylquinoxaline-6-carbohydrazide hybrids as potent α-glucosidase inhibitors

A novel series of diphenylquinoxaline-6-carbohydrazide hybrids 7a-o were rationally designed and synthesized as anti-diabetic agents. All synthesized compounds 7a-o were screened as possible α-glucosidase inhibitors and exhibited good inhibitory activity with IC50 values in the range of 110.6 ± 6.0 to 453.0 ± 4.7 µM in comparison with acarbose as the positive control (750.0 ± 10.5 µM). An exception in this trend came back to a compound 7k with IC50 value > 750 µM. Furthermore, the most potent derivative 7e bearing 3-fluorophenyl moiety was further explored by kinetic studies and showed the competitive type of inhibition. Additionally, the molecular docking of all derivatives was performed to get an insight into the binding mode of these derivatives within the active site of the enzyme. In silico assessments exhibited that 7e was well occupied in the binding pocket of the enzyme through favorable interactions with residues, correlating to the experimental results.

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.

Cyanoacetohydrazide linked to 1,2,3-triazole derivatives: a new class of α-glucosidase inhibitors

In this work, a novel series of cyanoacetohydrazide linked to 1,2,3-triazoles (9a–n) were designed and synthesized to be evaluated for their anti-α-glucosidase activity, focusing on the fact that α-glucosidase inhibitors have played a significant role in the management of type 2 diabetes mellitus. All synthesized compounds except 9a exhibited excellent inhibitory potential, with IC50 values ranging from 1.00 ± 0.01 to 271.17 ± 0.30 μM when compared to the standard drug acarbose (IC50 = 754.1 ± 0.5 μM). The kinetic binding study indicated that the most active derivatives 9b (IC50 = 1.50 ± 0.01 μM) and 9e (IC50 = 1.00 ± 0.01 μM) behaved as the uncompetitive inhibitors of α-glucosidase with Ki = 0.43 and 0.24 μM, respectively. Moreover, fluorescence measurements were conducted to show conformational changes of the enzyme after binding of the most potent inhibitor (9e). Calculation of standard enthalpy (ΔHm°) and entropy (ΔSm°) values confirmed the construction of hydrophobic interactions between 9e and the enzyme. Also, docking studies indicated desired interactions with important residues of the enzyme which rationalized the in vitro results.

Pharmacological exploration of triazole based therapeutics for Alzheimer disease: An overview

Abstract:

Alzheimer`s disease (AD) is an irreversible progressive neurodegenerative disorder which may account for approximately 60-70% cases of dementia worldwide. AD is characterized by impaired behavioural and cognitive functions including memory, language, conception, attentiveness, judgment, and reasoning problems. The two important hallmarks of AD are the appearance of plaques and tangles of amyloid beta (Aβ) and tau proteins, respectively, in the brain based on the etiology of the disease including cholinergic impairment, metal dyshomeostasis, oxidative stress, and degradation of neurotransmitters. Currently, the used medication only provides alleviation of symptoms but not effective in curing the disease that is creating by an urge to develop new molecules to treat AD. Heterocyclic compounds have proven their ability to be developed as drugs for the treatment of various diseases. The five-membered heterocyclic compound triazole has received foremost fascination for the discovery of new drugs due to the possibility of structural variation and proved its significance in various drug categories. Therefore, this review summarizes mainly the recent advancements in the development of novel 1,2,3-triazole and 1,2,4-triazole based molecules in the drug discovery process for targeting various AD targets such as phosphodiesterase 1 (PDE1) Inhibitors, Apoptosis signal-regulating kinase 1 (ASK1) inhibitors, Somatostatin receptor subtype-4 (SSTR4) agonist, many other druggable targets, molecular modelling studies as well as various methodology for the synthesis of triazoles containing molecules such as Click reaction, Pellizzari and Einhorn-Brunner Reaction.

Imino-2H-Chromene Based Derivatives as Potential Anti-Alzheimer's Agents: Design, Synthesis, Biological Evaluation and in Silico Study

A new series of imino-2H-chromene derivatives were rationally designed and synthesized as novel multifunctional agents against Alzheimer's disease. A set of phenylimino-2H-chromenes as well as the newly synthesized iminochromene derivatives were evaluated as BACE1, acetylcholinesterase (AChE), and butyrylcholinesterase (BuChE) inhibitors. The results indicated that among the iminochromene set, 10c bearing fluorobenzyl moiety was the most potent BACE1 inhibitor with an IC₅₀ value 6.31 μM. In vitro anti-cholinergic activities demonstrated that compound 10a bearing benzyl pendant was the best inhibitor of AChE (% inhibition at 30 μM=24.4) and BuChE (IC₅₀ =3.3 μM). Kinetic analysis of compound 10a against BuChE was also performed and showed a mixed-type inhibition pattern. The neuroprotective assessment revealed that compound 11b, a phenylimino-2H-chromene derivative with hydroxyethyl moiety, provided 32.3 % protection at 25 μM against Aβ-induced PC12 neuronal cell damage. In addition, docking and simulation studies of the most potent compounds against BACE1 and BuChE confirmed the experimental results.

Design and synthesis of phenoxymethybenzoimidazole incorporating different aryl thiazole-triazole acetamide derivatives as α-glycosidase inhibitors

A novel series of phenoxymethybenzoimidazole derivatives (9a-n) were rationally designed, synthesized, and evaluated for their α-glycosidase inhibitory activity. All tested compounds displayed promising α-glycosidase inhibitory potential with IC₅₀ values in the range of 6.31 to 49.89 μM compared to standard drug acarbose (IC₅₀ = 750.0 ± 10.0 μM). Enzyme kinetic studies on 9c, 9g, and 9m as the most potent compounds revealed that these compounds were uncompetitive inhibitors into α-glycosidase. Docking studies confirmed the important role of benzoimidazole and triazole rings of the synthesized compounds to fit properly into the α-glycosidase active site. This study showed that this scaffold can be considered as a highly potent α-glycosidase inhibitor.

Synthesis and evaluation of novel arylisoxazoles linked to tacrine moiety: in vitro and in vivo biological activities against Alzheimer's disease

Alzheimer's disease (AD) is now ranked as the third leading cause of death after heart disease and cancer. There is no definite cure for AD due to the multi-factorial nature of the disease, hence, multi-target-directed ligands (MTDLs) have attracted lots of attention. In this work, focusing on the efficient cholinesterase inhibitory activity of tacrine, design and synthesis of novel arylisoxazole-tacrine analogues was developed. In vitro acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) inhibition assay confirmed high potency of the title compounds. Among them, compounds 7l and 7b demonstrated high activity toward AChE and BChE with IC₅₀ values of 0.050 and 0.039 μM, respectively. Both compounds showed very good self-induced Aβ aggregation and AChE-induced inhibitory activity (79.4 and 71.4% for compound 7l and 61.8 and 58.6% for compound 7b, respectively). Also, 7l showed good anti-BACE1 activity with IC₅₀ value of 1.65 µM. The metal chelation test indicated the ability of compounds 7l and 7b to chelate biometals (Zn²⁺, Cu²⁺, and Fe²⁺). However, they showed no significant neuroprotectivity against Aβ-induced damage in PC12 cells. Evaluation of in vitro hepatotoxicity revealed comparable toxicity of compounds 7l and 7b with tacrine. In vivo studies by Morris water maze (MWM) task demonstrated that compound 7l significantly reversed scopolamine-induced memory deficit in rats. Finally, molecular docking studies of compounds 7l and 7b confirmed establishment of desired interactions with the AChE, BChE, and BACE1 active sites.

Anti-melanogenesis and anti-tyrosinase properties of aryl-substituted acetamides of phenoxy methyl triazole conjugated with thiosemicarbazide: Design, synthesis and biological evaluations

A series of aryl phenoxy methyl triazole conjugated with thiosemicarbazides were designed, synthesized, and evaluated for their tyrosinase inhibitory activities in the presence of l-dopa and l-tyrosine as substrates. All the compounds showed tyrosinase inhibition in the sub-micromolar concentration. Among the derivatives, compound 9j bearing benzyl displayed exceptionally high potency against tyrosinase with IC₅₀ value of 0.11 μM and 0.17 μM in the presence of l-tyrosine and l-dopa as substrates which is significantly lower than that of kojic acid as the positive control with an IC₅₀ value of 9.28 μM for l-tyrosine and 9.30 μM for l-dopa. According to Lineweaver-Burk plot, 9j demonstrated an uncompetitive type of inhibition in the kinetic assay. Also, in vitro antioxidant activities determined by DPPH assay recorded an IC₅₀ value of 68.43 μM for 9i. The melanin content of 9j was determined on B16F10 melanoma human cells which demonstrated a significant reduction of the melanin content. Moreover, the binding energies corresponding to the same ligand as well as computer-aided drug-likeness and pharmacokinetic studies were also carried out. Compound 9j also possessed metal chelation potential correlated to its high anti-TYR activity.

Design and synthesis of multi-target directed 1,2,3-triazole-dimethylaminoacryloyl-chromenone derivatives with potential use in Alzheimer's disease

To discover multifunctional agents for the treatment of Alzheimer's disease (AD), a new series of 1,2,3-triazole-chromenone derivatives were designed and synthesized based on the multi target-directed ligands approach. The in vitro biological activities included acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) inhibition as well as anti-Aβ aggregation, neuroprotective effects, and metal-chelating properties. The results indicated a highly selective BuChE inhibitory activity with an IC₅₀ value of 21.71 μM for compound 10h as the most potent compound. Besides, compound 10h could inhibit self-induced Aβ_1–42 aggregation and AChE-induced Aβ aggregation with 32.6% and 29.4% inhibition values, respectively. The Lineweaver–Burk plot and molecular modeling study showed that compound 10h targeted both the catalytic active site (CAS) and peripheral anionic site (PAS) of BuChE. It should be noted that compound 10h was able to chelate biometals. Thus, the designed scaffold could be considered as multifunctional agents in AD drug discovery developments.