Synthesis and evaluation of novel 1,2,3-triazole-based acetylcholinesterase inhibitors with neuroprotective activity

Discovery of cinnamamide/ester triazole hybrids as potential treatment for Alzheimer's disease

Developing multitargeted ligands as promising therapeutics for Alzheimer's disease (AD) has been considered important. Herein, a novel class of cinnamamide/ester-triazole hybrids with multifaceted effects on AD was developed based on the multitarget-directed ligands strategy. Thirty-seven cinnamamide/ester-triazole hybrids were synthesized, with most exhibiting significant inhibitory activity against Aβ-induced toxicity at a single concentration in vitro. The most optimal hybrid compound 4j inhibited copper-induced Aβ toxicity in AD cells. its action was superior to that of donepezil and memantine. It also moderately inhibited intracellular AChE activity and presented favorable bioavailability and blood-brain barrier penetration with low toxicity in vivo. Of note, it ameliorated cognitive impairment, neuronal degeneration, and Aβ deposition in Aβ1-42-injured mice. Mechanistically, the compound regulated APP processing by promoting the ADAM10-associated nonamyloidogenic signaling and inhibiting the BACE1-mediated amyloidogenic pathway. Moreover, it suppressed intracellular AChE activity and tau phosphorylation. Therefore, compound 4j may be a promising multitargeted active molecule against AD.

Discovery of triazole-bridged aryl adamantane analogs as an intriguing class of multifunctional agents for treatment of Alzheimer's disease

Alzheimer's disease (AD) is a progressive brain disorder associated with slow loss of brain functions leading to memory failure and modest changes in behavior. The multifactorial neuropathological condition is due to a depletion of cholinergic neurons and accumulation of amyloid-beta (Aβ) plaques. Recently, a multi-target-directed ligand (MTDL) strategy has emerged as a robust drug discovery tool to overcome current challenges. In this research work, we aimed to design and develop a library of triazole-bridged aryl adamantane analogs for the treatment of AD. All synthesized analogs were characterized and evaluated through various in vitro and in vivo biological studies. The optimal compounds 32 and 33 exhibited potent inhibitory activities against acetylcholinesterase (AChE) (32 - IC50 = 0.086 μM; 33 - 0.135 μM), and significant Aβ aggregation inhibition (20 μM). N-methyl-d-aspartate (NMDA) receptor (GluN1-1b/GluN2B subunit combination) antagonistic activity of compounds 32 and 33 measured upon heterologous expression in Xenopus laevis oocytes showed IC50 values of 3.00 μM and 2.86 μM, respectively. The compounds possessed good blood-brain barrier permeability in the PAMPA assay and were safe for SH-SY5Y neuroblastoma (10 μM) and HEK-293 cell lines (30 μM). Furthermore, in vivo behavioral studies in rats demonstrated that both compounds improved cognitive and spatial memory impairment at a dose of 10 mg/kg oral administration. Together, our findings suggest triazole-bridged aryl adamantane as a promising new scaffold for the development of anti-Alzheimer's drugs.

Review of triazole scaffolds for treatment and diagnosis of Alzheimer's disease

Triazole scaffolds, a series of 5-membered heterocycles, are well known for their high efficacy, low toxicity, and superior pharmacokinetics. Alzheimer's disease (AD) is the first neurodegenerative disorder with complex pathological mechanisms. Triazole, as an aromatic group with three nitrogen atoms, forms polar and non-polar interactions with diverse key residues in the receptor-ligand binding procedure, and has been widely used in the molecular design in the development of anti-AD agents. Moreover, considering the simple synthesis approaches, triazole scaffolds are commonly used to link two pharmacodynamic groups in one chemical molecule, forming multi-target directed ligands (MTDLs). Furthermore, the click reaction between azide- and cyano-modified enzyme and ligand provides feasibility for the new modulator discovery, compound tissue distribution evaluation, enzyme localization, and pharmacological mechanism study, promoting the diagnosis of AD course.

An Overview of 1,2,3-triazole-Containing Hybrids and Their Potential Anticholinesterase Activities

Acetylcholine (ACh) neurotransmitter of the cholinergic system in the brain is involved in learning, memory, stress responses, and cognitive functioning. It is hydrolyzed into choline and acetic acid by two key cholinesterase enzymes, viz., acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE). A loss or degeneration of cholinergic neurons that leads to a reduction in ACh levels is considered a significant contributing factor in the development of neurodegenerative diseases (NDs) such as Alzheimer's disease (AD). Numerous studies have shown that cholinesterase inhibitors can raise the level of ACh and, therefore, enhance people's quality of life, and, at the very least, it can temporarily lessen the symptoms of NDs. 1,2,3-triazole, a five-membered heterocyclic ring, is a privileged moiety, that is, a central scaffold, and is capable of interacting with a variety of receptors and enzymes to exhibit a broad range of important biological activities. Recently, it has been clubbed with other pharmacophoric fragments/molecules in hope of obtaining potent and selective AChE and/or BuChE inhibitors. The present updated review succinctly summarizes the different synthetic strategies used to synthesize the 1,2,3-triazole moiety. It also highlights the anticholinesterase potential of various 1,2,3-triazole di/trihybrids reported in the past seven years (2015-2022), including a rationale for hybridization and with an emphasis on their structural features for the development and optimization of cholinesterase inhibitors to treat NDs.

Modulation of inflammatory mediators involved in the antinociceptive and anti-inflammatory effects of a new thioamide derivative: thiocyanoacetamide

Inflammatory pain is part of the body's defense mechanism and plays an important role in the healing process. Although some drugs are efficient and intensively used for their potent anti-inflammatory properties, they present problematic side effects. The aim of this study was to evaluate the anti-nociceptive effect of the thiocyanoacetamide (Thm) compared to paracetamol (Para), dexamethasone (Dex) and morphine (Morph) and to study inflammatory mediators on models of acute inflammatory pain in rats using the formalin injection test in the hind paw of rats as chemical stimulus. The obtained results showed significant modulation of pain by Thm pretreatment with a maximum at an effective dose (10 mg/kg) proved by the absence of licking and biting of the affected paw during the early and late phases of inflammation. This effect was comparable to Dex at 10 mg/kg, Para at 400 mg/kg and less than Morph at 5 mg/kg pretreatment doses. The study of anti-inflammatory targets showed that Thm pretreatment maintained plasma serotonin release at normal level compared to the negative control group (T-) and corrected the decrease in the plasma level of prostaglandins after inflammatory induction with no variation in the level of histamine in different groups. The evaluation of inflammation mediators demonstrated that the pretreatment with Thm induced the decrease in the amount of both IL-1 Beta and TNF alpha in plasma and the increase in their amount in the tissue of the injection site. The Thm has been promoted as an anti-nociceptive drug that induces modulation of inflammatory mediators.

Design, synthesis, and structure-activity relationship of caffeine-based triazoles as dual AChE and BACE-1 inhibitors

Natural products have significantly contributed to drug discovery for neurodegenerative diseases. Caffeine is one of the well-known central nervous system(CNS)-active natural products. Besides its CNS stimulant properties, it is a mild inhibitor of acetylcholinesterase (AChE) and possesses memory-enhancing properties. The present work aimed to improve the AChE inhibition activity of the caffeine. The rationally designed caffeine-based triazoles were synthesized and evaluated in vitro for cholinesterase and β-site amyloid precursor protein cleaving enzyme-1 (BACE-1) inhibitory activities. The attachment of triazole to the caffeine enhances its AChE inhibition activity from half-maximal inhibitory concentration (IC₅₀ ) of 129 µM to 0.49 µM (derivative, 6l). The caffeine core interacts with the peripheral anionic site, whereas the benzyl triazole occupies the catalytic anionic site located at the bottom of the active site gorge. The structure-activity relationship revealed that the four-atom ester linker is superior to shorter linkers for connecting the caffeine core to the triazole. The 2,6-difluorobenzyl triazole-linked caffeine derivative, 6d, exhibits dual inhibition of AChE and BACE-1 with IC₅₀ values of 1.43 and 10.9 µM, respectively. The derivative 6d inhibits AChE via a mixed-type mode with an inhibition rate constant (K_i ) value of 2.35 μM, which was corroborated by docking studies. The triazole 6d has an acceptable stability profile in human liver microsomes (t_1/2  = 54 min) and was found to possess CNS permeability when evaluated using the parallel artificial membrane permeability blood-brain barrier assay. The results presented herein warrant investigating caffeine-based triazoles in preclinical models of Alzheimer's disease.

Anti-Inflammatory Activity of 4-(4-(Heptyloxy)phenyl)-2,4-dihydro-3H-1,2,4-triazol-3-one via Repression of MAPK/NF-κB Signaling Pathways in β-Amyloid-Induced Alzheimer's Disease Models

Alzheimer’s disease (AD) is a major neurodegenerative disease, but so far, it can only be treated symptomatically rather than changing the process of the disease. Recently, triazoles and their derivatives have been shown to have potential for the treatment of AD. In this study, the neuroprotective effects of 4-(4-(heptyloxy)phenyl)-2,4-dihydro-3H-1,2,4-triazol-3-one (W112) against β-amyloid (Aβ)-induced AD pathology and its possible mechanism were explored both in vitro and in vivo. The results showed that W112 exhibits a neuroprotective role against Aβ-induced cytotoxicity in PC12 cells and improves the learning and memory abilities of Aβ-induced AD-like rats. In addition, the assays of the protein expression revealed that W112 reversed tau hyperphosphorylation and reduced the production of proinflammatory cytokines, tumor necrosis factor-α and interleukin-6, both in vitro and in vivo studies. Further study indicated that the regulation of mitogen-activated protein kinase/nuclear factor-κB pathways played a key role in mediating the neuroprotective effects of W112 against AD-like pathology. W112 may become a potential drug for AD intervention.

Synthesis of novel immunomodulatory 1,4-disubstituted bis-1,2,3-triazoles by using click chemistry and their intracellular mechanism of action

In this study, six new 1,4-disubstituted bis-1,2,3-triazole compounds, N,N'-(1,2-phenylene)bis(2-(4-R-1H-1,2,3-triazol-1-yl)acetamide), were synthesized with high yield (88-96 %) by using click chemistry and their molecular structures were characterized by using NMR, FT-IR, HRMS and elemental analysis techniques. Previous studies suggest anti-inflammatory and analgesic activities for different 1,2,3-triazole derivatives and in the light of those studies we aimed to examine these novel derivatives immunomodulatory activities on the mammalian macrophages. Pro-inflammatory cytokines (TNF, IL6, GMCSF and IL12p40) secretion levels were tested in the presence of bis-1,2,3-triazole compounds when the macrophages were activated with LPS. These new derivatives were able to suppress the production of these cytokines at different levels. Intracellular phophorylated PI3K protein levels were measured due to its prominent role in inflammatory reactions. Our flow cytometry analysis results suggested that some of these compounds were partially effective through PI3K pathway. In different inflammatory and autoimmune disease settings these novel 1,2,3-triazole derivatives can be utilized as non-steroid based anti-inflammatory drug candidates.

New 1,2,3-Triazole-genipin Analogues and Their Anti-Alzheimer's Activity

A novel series of 1,2,3-triazole-genipin analogues were designed, synthesized, and evaluated for neuroprotective activity, acetylcholinesterase (AChE), and butyrylcholinesterase (BuChE) inhibitory activity. The genipin analogues bearing bromoethyl- and diphenylhydroxy-triazole showed in vitro neuroprotective properties against H₂O₂ toxicity along with potent inhibitory activity on BuChE with IC₅₀ values of 31.77 and 54.33 μM, respectively, compared with galantamine (IC₅₀ = 34.05 μM). The molecular docking studies of these genipin analogues showed good binding energy and interact well with the key amino acids of BuChE via hydrogen-bonding and hydrophobic interactions. Triazole genipins might be promising lead compounds as anti-Alzheimer's agents.

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.

Acetylcholinesterase Enzyme Inhibitor Molecules with Therapeutic Potential for Alzheimer's Disease

Acetylcholinesterase (AchE), hydrolase enzyme, regulates the hydrolysis of acetylcholine neurotransmitter in the neurons. AchE is found majorly in the central nervous system at the site of cholinergic neurotransmission. It is involved in the pathophysiology of Alzheimer's diseasecausing dementia, cognitive impairment, behavioral and psychological symptoms. Recent findings involved the inhibition of AchE that could aid in the treatment of Alzheimer's. Many drugs of different classes are being analyzed in the clinical trials and examined for their potency. Drugs that are used in the treatment of Alzheimer's disease are donepezil, galantamine, tacrine, rivastigmine showing major adverse effects. To overcome this, researchers work on novel drugs to elicit inhibition. This review comprises many hybrids and non-hybrid forms of heteroaromatic and nonheteroaromatic compounds that were designed and evaluated for AchE inhibition by Ellman's method of assay. These novel compounds may assist future perspectives in the discovery of novel moieties against Alzheimer's disease by the inhibition of AchE.

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.

Autophagy Induced by a Novel Triazol Derivative Promotes Angiogenesis Through Decreasing Interferon-Inducible Protein 10 Level in Vascular Endothelial Cells

ABSTRACT

Autophagy plays an important role in angiogenesis, whereas the mechanisms of vascular endothelial cell (VEC) autophagy associated with angiogenesis remain unclear. In this study, we identified a novel triazol derivative (JL025) that significantly promoted angiogenesis both in vitro and in vivo. Moreover, JL025 had no effects on cell proliferation but dramatically increased the autophagy level of VEC. The suppression of autophagy inhibited JL025-induced angiogenesis in vitro and in vivo, suggesting that JL025-induced angiogenesis was dependent on the enhanced autophagy. Mechanistic studies indicated that JL025-induced VEC autophagy was related to the Protein Kinase B/mTOR signaling pathway. Meanwhile, JL025 decreased the antiangiogenic chemokine interferon-inducible protein 10 (IP10) protein level in human VECs. Importantly, the suppression of autophagy inhibited JL025-induced decrease of IP10 protein level, indicating that autophagy mediated the degradation of IP10. Taken together, our findings provide new insights into the relationship of VEC autophagy with angiogenesis, and JL025 may have a therapeutic potential in related diseases.

Design, synthesis and in-vitro evaluation of fluorinated triazoles as multi-target directed ligands for Alzheimer disease

Alzheimer disease is multi-factorial and inflammation plays a major role in the disease progression and severity. Metals and reactive oxygen species (ROS) are the key mediators for inflammatory conditions associated with Alzheimer's. Along multi-factorial nature, major challenge for developing new drug is the ability of the molecule to cross blood brain barrier (BBB). We have designed and synthesized multi-target directed hexafluorocarbinol containing triazoles to inhibit Amyloid β aggregation and simultaneously chelate the excess metals present in the extracellular space and scavenge the ROS thus reduce the inflammatory condition. From the screened compound library, compound 1c found to be potent and safe. It has demonstrated inhibition of Amyloid β aggregation (IC₅₀ of 4.6 μM) through selective binding with Amyloid β at the nucleation site (evidenced from the molecular docking). It also chelate metals (Cu⁺², Zn⁺² and Fe⁺³) and scavenges ROS significantly. Due to the presence of hexafluorocarbinol moiety in the molecule it may assist to permeate BBB and improve the pharmacokinetic properties. The in-vitro results of compound 1c indicate the promiscuity for the development of hexafluorocarbinol containing triazoles amide scaffold as multi-target directed therapy against Alzheimer disease.

Triazole analogues as potential pharmacological agents: a brief review

Background

A large number of studies have recently reported that, because of their significant biological and pharmacological properties, heterocyclic compounds and their derivatives have attracted a strong interest in medicinal chemistry. The triazole nucleus is one of the most important heterocycles which has a feature of natural products as well as medicinal agents. Heterocyclic nitrogen is abundantly present in most medicinal compounds. The derivatization of triazole ring is based on the phenomenon of bio-isosteres in which substituted the oxygen atom of oxadiazole nucleus with nitrogen triazole analogue.

Main text

This review focuses on recent synthetic procedure of triazole moiety, which comprises of various pharmacological activities such as antimicrobial, anticonvulsant, anti-inflammatory, analgesic, antitubercular, anthelmintic, antioxidant, antimalarial, antiviral, etc..

Conclusion

This review highlights the current status of triazole compounds as different multi-target pharmacological activities. From the literature survey, triazole is the most widely used compound in different potential activities.

15β-Senecioyl-oxy-ent-kaur-16-en-19-oic Acid, a Diterpene Isolated from Baccharis lateralis, as Promising Oral Compound for the Treatment of Schistosomiasis

Praziquantel is the only available drug to treat schistosomiasis, and therefore, urgent studies must be performed to identify new anthelmintic agents. This study reports the anthelmintic evaluation of two related ent-kaurane diterpenes isolated from aerial parts of Baccharis lateralis (Asteraceae), ent-kaur-16-en-19-oic acid (1) and 15β-senecioyl-oxy-ent-kaur-16-en-19-oic acid (2) against Schistosoma mansoni in vitro and in a murine model of schistosomiasis. Both compounds exhibited in vitro activity with lethal concentration 50% (LC₅₀) values of 26.1 μM (1) and 11.6 μM (2) as well as reduced toxicity against human cell lines, revealing a good selectivity profile, mainly with compound 2 (selectivity index > 10). Compound 2 also decreased egg production and caused morphological alterations in the parasite reproductive system. In mice infected with S. mansoni, oral treatment with compound 2 at 400 mg/kg, the standard dose used in this model of schistosomiasis, caused a significant reduction in a total worm burden of 61.9% (P < 0.01). S. mansoni egg production, a key mechanism for both transmission and pathogenesis, was also markedly reduced. In addition, compound 2 achieved a significant reduction in hepatosplenomegaly. Therefore, the diterpene 15β-senecioyl-oxy-ent-kaur-16-en-19-oic acid (2) has an acceptable cytotoxicity profile and is orally active in a murine schistosomiasis model.

Vitamin B3-Based Biologically Active Compounds as Inhibitors of Human Cholinesterases

We evaluated the potential of nine vitamin B3 scaffold-based derivatives as acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) inhibitors, as a starting point for the development of novel drugs for treating disorders with cholinergic neurotransmission-linked pathology. As the results indicate, all compounds reversibly inhibited both enzymes in the micromolar range pointing to the preference of AChE over BChE for binding the tested derivatives. Molecular docking studies revealed the importance of interactions with AChE active site residues Tyr337 and Tyr124, which dictated most of the observed differences. The most potent inhibitor of both enzymes with K_i of 4 μM for AChE and 8 μM for BChE was the nicotinamide derivative 1-(4′-phenylphenacyl)-3-carbamoylpyridinium bromide. Such a result places it within the range of several currently studied novel cholinesterase inhibitors. Cytotoxicity profiling did not classify this compound as highly toxic, but the induced effects on cells should not be neglected in any future detailed studies and when considering this scaffold for drug development.

Tyrosol 1,2,3-triazole analogues as new acetylcholinesterase (AChE) inhibitors

The present work proposed the preparation of triazolic analogues of tyrosol, a biophenol found in olive oil and whose wide range of bioactivities has been the target of many studies. We obtained fifteen novel tyrosol derivatives and the compounds of the series were later evaluated as acetylcholinesterase (AChE) inhibitors. The study of AChE inhibition is important for the development of new drugs and pesticides, and especially the research for managing Alzheimer's disease. The most active compound, namely 7-({1-[2-(4-hydroxyphenyl)ethyl]-1H-1,2,3-triazol-4-yl}methoxy)-4-methyl-2H-chromen-2-one (30), showed IC₅₀ value of 14.66 ± 2.29 μmol L^-1. Docking experiments corroborated by kinetic assay are suggestive of a competitive inhibition mechanism. Derivatives interacted with amino acids from the AChE active site associated to the development of Alzheimer's disease. The results indicate that the compounds synthesized have a high potential as prototypes for the development of new acetylcholinesterase inhibitors.

Synthesis and bioactivities of 1-(4-hydroxyphenyl)-2-((heteroaryl)thio)ethanones as carbonic anhydrase I, II and acetylcholinesterase inhibitors

The discovery of enzyme targeting inhibitors is a popular area of drug research. Biological activities of the compounds bearing phenol and heteroaryl groups make them popular groups in drug design targeting important enzymes such as acetylcholinesterase (AChE, E.C.3.1.1.7) and carbonic anhydrases (CAs, EC 4.2.1.1). 1-(4-hydroxyphenyl)- 2-((aryl)thio)ethanones as possible AChE and CAs inhibitors were synthesized, and their chemical structures were confirmed by IR, 1H NMR, 13C NMR, and HRMS. The compounds 2 and 4 were found potent AChE inhibitors with the Ki values of 22.13 ±1.96 nM and 23.71 ±2.95 nM, respectively, while the compounds 2 (Ki = 8.61 ±0.90 nM, on hCA I) and 1 (Ki = 8.76 ±0.84 nM, on hCA II) had considerable CAs inhibitory potency. The lead compounds may help the scientists for the rational designing of an innovative class of drug candidates targeting enzyme-based diseases.

Design and synthesis of benzodiazepine-1,2,3-triazole hybrid derivatives as selective butyrylcholinesterase inhibitors

A new series of compounds based on benzodiazepine-1,2,3-triazole were synthesized and evaluated as cholinesterase inhibitors by Ellman's method. The compounds proved to be selective inhibitors of butyrylcholinesterase (BuChE) over acetylcholinesterase. The most potent compound was 3,3-dimethyl-11-(3-((1-(4-nitrobenzyl)-1H-1,2,3-triazol-4-yl)methoxy)phenyl)-2,3,4,5,10,11-hexahydro-1H-dibenzo[b,e][1,4]diazepin-1-one, identified as a submicromolar inhibitor of BuChE with IC₅₀ value of 0.2 µM. In addition, the amyloid-β self-aggregation evaluation studies for selected compounds showed potent inhibitory effects compared to donepezil. The docking and cell viability studies supported the potential of compound 9b-6 as significant BuChE inhibitor.

Exploring the Chemistry and Therapeutic Potential of Triazoles: A Comprehensive Literature Review

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Triazole is a valuable platform in medicinal chemistry, possessing assorted pharmacological properties, which could play a major role in the common mechanisms associated with various disorders like cancer, infections, inflammation, convulsions, oxidative stress and neurodegeneration. Structural modification of this scaffold could be helpful in the generation of new therapeutically useful agents. Although research endeavors are moving towards the growth of synthetic analogs of triazole, there is still a lot of scope to achieve drug discovery break-through in this area. Upcoming therapeutic prospective of this moiety has captured the attention of medicinal chemists to synthesize novel triazole derivatives. The authors amalgamated the chemistry, synthetic strategies and detailed pharmacological activities of the triazole nucleus in the present review. Information regarding the marketed triazole derivatives has also been incorporated. The objective of the review is to provide insights to designing and synthesizing novel triazole derivatives with advanced and unexplored pharmacological implications.

Critical evaluation of current Alzheimer's drug discovery (2018-19) & futuristic Alzheimer drug model approach

Alzheimer's disease (AD), a neurodegenerative disease responsible for death of millions of people worldwide is a progressive clinical disorder which causes neurons to degenerate and ultimately die. It is one of the common causes of dementia wherein a person's incapability to independently think, behave and decline in social skills can be quoted as major symptoms. However the early signs include the simple non-clinical symptoms such as forgetting recent events and conversations. Onset of these symptoms leads to worsened conditions wherein the AD patient suffers severe memory impairment and eventually becomes unable to work out everyday tasks. Even though there is no complete cure for AD, rigorous research has been going on to reduce the progress of AD. Currently, a very few clinical drugs are prevailing for AD treatment. So this is the need of hour to design, develop and discovery of novel anti-AD drugs. The main factors for the cause of AD according to scientific research reveals structural changes in brain proteins such as beta amyloid, tau proteins into plaques and tangles respectively. The abnormal proteins distort the neurons. Despite the high potencies of the synthesized molecules; they could not get on the clinical tests up to human usage. In this review article, the recent research carried out with respect to inhibition of AChE, BuChE, NO, BACE1, MAOs, Aβ, H3R, DAPK, CSF1R, 5-HT4R, PDE, σ₁R and GSK-3β is compiled and organized. The summary is focused mainly on cholinesterases, Aβ, BACE1 and MAOs classes of potential inhibitors. The review also covers structure activity relationship of most potent compounds of each class of inhibitors alongside redesign and remodeling of the most significant inhibitors in order to expect cutting edge inhibitory properties towards AD. Alongside the molecular docking studies of the some final compounds are discussed.

Discovery of New Selective Butyrylcholinesterase (BChE) Inhibitors with Anti-Aβ Aggregation Activity: Structure-Based Virtual Screening, Hit Optimization and Biological Evaluation

In this study, a series of selective butyrylcholinesterase (BChE) inhibitors was designed and synthesized from the structural optimization of hit 1, a 4-((3,4-dihydroisoquinolin-2(1H)-yl)methyl)benzoic acid derivative identified by virtual screening our compound library. The in vitro enzyme assay results showed that compounds 9 ((4-((3,4-dihydroisoquinolin-2(1H)-yl)methyl)phenyl)(pyrrolidin-1-yl)methanone) and 23 (N-(2-bromophenyl)-4-((3,4-dihydroisoquinolin-2(1H)-yl)methyl)benzamide) displayed improved BChE inhibitory activity and good selectivity towards BChE versus AChE. Their binding modes were probed by molecular docking and further validated by molecular dynamics simulation. Kinetic analysis together with molecular modeling studies suggested that these derivatives could target both the catalytic active site (CAS) and peripheral anionic site (PAS) of BChE. In addition, the selected compounds 9 and 23 displayed anti-Aβ_1–42 aggregation activity in a dose-dependent manner, and they did not show obvious cytotoxicity towards SH-SY5Y neuroblastoma cells. Also, both compounds showed significantly protective activity against Aβ_1-42-induced toxicity in a SH-SY5Y cell model. The present results provided a new valuable chemical template for the development of selective BChE inhibitors.

Novel Role of Heterogeneous Nuclear Ribonucleoprotein E1 in Regulation of Apoptosis and Autophagy by a Triazole Derivative in Vascular Endothelial Cells

Vascular endothelial cell (VEC) apoptosis and autophagy play an important role in the maintenance of vascular homeostasis. However, the association of molecular mechanisms between vascular endothelial cell apoptosis and autophagy has not been clarified. Here, we identified a novel triazole derivative, JL014, which could inhibit human umbilical vein vascular endothelial cell (HUVEC) apoptosis induced by deprivation of serum and fibroblast growth factor 2 and maintain HUVEC survival by promoting autophagy. Importantly, JL014 increased the mRNA and protein level of heterogeneous nuclear ribonucleoprotein E1 (hnRNP E1) in HUVECs. In addition, knockdown of hnRNP E1 by RNA interference inhibited the effects of JL014 on VEC apoptosis and autophagy. Furthermore, we investigated the effect of JL014 on the expression of HMBOX1, a key VEC apoptosis inhibitor and autophagy inducer by inhibiting mTOR signaling and the level of cleaved caspase-3. Our results demonstrated that JL014 enhanced mRNA transcription and increased protein synthesis of HMBOX1. JL014 also inhibited mTOR signaling and the cleaved caspase-3 level. Mechanistic studies revealed that hnRNP E1 could bind to the promoter and 5'UTR of HMBOX1 and active HMBOX1 expression. Therefore, our results firmly establish hnRNP E1 as a new regulator of VEC apoptosis and autophagy through mediating HMBOX1 expression, and opened the door to a novel therapeutic drug for related vascular diseases.

Molecular-docking-guided design and synthesis of new IAA-tacrine hybrids as multifunctional AChE/BChE inhibitors

A series of new indole-3-acetic acid (IAA)-tacrine hybrids as dual acetylcholinesterase (AChE)/butyrylcholinesterase (BChE) inhibitors were designed and prepared based on the molecular docking mode of AChE with an IAA derivative (1a), a moderate AChE inhibitor identified by screening our compound library for anti-Alzheimer's disease (AD) drug leads. The enzyme assay results revealed that some hybrids, e.g. 5d and 5e, displayed potent dual in vitro inhibitory activities against AChE/BChE with IC₅₀ values in low nanomolar range. Molecular modeling studies in tandem with kinetic analysis suggest that these hybrids target both catalytic active site and peripheral anionic site of cholinesterase (ChE). Molecular dynamic simulations and Molecular Mechanics/Poisson-Boltzmann Surface Area (MM-PBSA) calculations indicate that 5e has more potent binding affinity than hit 1a, which may explain the stronger inhibitory effect of 5e on AChE. Furthermore, their predicted pharmacokinetic properties and in vitro influences on mouse brain neural network electrical activity were discussed. Taken together, compound 5e can be highlighted as a lead compound worthy of further optimization for designing new anti-AD drugs.

Total Synthesis of Pulmonarin B and Design of Brominated Phenylacetic Acid/Tacrine Hybrids: Marine Pharmacophore Inspired Discovery of New ChE and Aβ Aggregation Inhibitors

A marine natural product, pulmonarin B (1), and a series of related tacrine hybrid analogues were synthesized and evaluated as cholinesterase (ChE) inhibitors. The in vitro ChE assay results revealed that 1 showed moderate dual acetylcholinesterase (AChE)/ butyrylcholinesterase (BChE) inhibitory activity, while the hybrid 12j proved to be the most potent dual inhibitor among the designed derivatives, being almost as active as tacrine. Molecular modeling studies together with kinetic analysis suggested that 12j interacted with both the catalytic active site and peripheral anionic site of AChE. Compounds 1 and 12j could also inhibit self-induced and AChE-induced Aβ aggregation. In addition, the cell-based assay against the human hepatoma cell line (HepG2) revealed that 1 and 12j did not show significant hepatotoxicity compared with tacrine and donepezil. Taken together, the present study confirmed that compound 1 was a potential anti-Alzheimer's disease (AD) hit, and 12j could be highlighted as a multifunctional lead compound for anti-AD drug development.

New Octadecanoid Enantiomers from the Whole Plants of Plantago depressa

In this study, 19 octadecanoid derivatives-four pairs of enantiomers (1⁻8), two racemic/scalemic mixtures (9⁻10), and nine biosynthetically related analogues-were obtained from the ethanolic extract of a Chinese medicinal plant, Plantago depressa Willd. Their structures were elucidated on the basis of detailed spectroscopic analyses, with the absolute configurations of the new compounds assigned by time-dependent density functional theory (TD-DFT)-based electronic circular dichroism (ECD) calculations. Six of them (1, 3⁻6, and 9) were reported for the first time, while 2, 7, and 8 have been previously described as derivatives and are currently obtained as natural products. Our bioassays have established that selective compounds show in vitro anti-inflammatory activity by inhibiting lipopolysaccharide-induced nitric oxide (NO) production in mouse macrophage RAW 264.7 cells.

Design, synthesis and biological evaluation of novel 1,2,3-triazole linked coumarinopyrazole conjugates as potent anticholinesterase, anti-5-lipoxygenase, anti-tyrosinase and anti-cancer agents

A series of new 1,2,3-triazole linked coumarinopyrazole conjugates 4a-e and 5a-e have been synthesized via the Copper(I)-catalysed Alkyne-Azide Cycloaddition (CuAAC). Going through the reaction of compound 2 with the 3-propargyl bromide gave a mixture of propargylated regioisomers 3 + 3' used as a dipolarophile to access to triazoles 4a-e and 5a-e. The structures of the prepared cycloadducts were determined by ¹H, ¹³C and 2D-NMR techniques and by HRMS analysis. All the synthesized derivatives have been evaluated for their anticholinesterase, anti-5-lipoxygenase, anti-tyrosinase, and cytotoxic activities.

Bioactive Pyridone Alkaloids from a Deep-Sea-Derived Fungus Arthrinium sp. UJNMF0008

Eight new 4-hydroxy-2-pyridone alkaloids arthpyrones D⁻K (1⁻8), along with two known analogues apiosporamide (9) and arthpyrone B (10), were isolated from a deep-sea-derived fungus Arthrinium sp. UJNMF0008. The structures of the isolated compounds were elucidated on the basis of spectroscopic methods with that of 1 being established by chemical transformation and X-ray diffraction analysis. Compounds 1 and 2 bore an ester functionality linking the pyridone and decalin moieties first reported in this class of metabolites, while 3 and 4 incorporated a rare natural hexa- or tetrahydrobenzofuro[3,2-c]pyridin-3(2H)-one motif. Compounds 3⁻6 and 9 exhibited moderate to significant antibacterial activity against Mycobacterium smegmatis and Staphylococcus aureus with IC₅₀ values ranging from 1.66⁻42.8 μM, while 9 displayed cytotoxicity against two human osteosarcoma cell lines (U2OS and MG63) with IC₅₀ values of 19.3 and 11.7 μM, respectively.

A facile water-stable MOF-based “off–on” fluorescent switch for label-free detection of dopamine in biological fluid

An Abtz–CdI₂–MOF was developed as an “off–on” fluorescent switch for label-free detection of dopamine without any surface modification or functionalization.