Development of Multifunctional Pyrimidinylthiourea Derivatives as Potential Anti-Alzheimer Agents

Discovery of novel quinolin-2-one derivatives as potential GSK-3β inhibitors for treatment of Alzheimer's disease: Pharmacophore-based design, preliminary SAR, in vitro and in vivo biological evaluation

Recently, glycogen synthase kinase-3β (GSK-3β) has been considered as a critical factor implicated in Alzheimer's disease (AD). In a previous work, a 3D pharmacophore model for GSK-3β inhibitors was created and the results suggested that derivative ZINC67773573, VIII, may provide a promising lead for developing novel GSK-3β inhibitors for the AD's treatment. Consequently, in this work, novel series of quinolin-2-one derivatives were synthesized and assessed for their GSK-3β inhibitory properties. In vitro screening identified three compounds: 7c, 7e and 7f as promising GSK-3β inhibitors. Compounds 7c, 7e and 7f were found to exhibit superior inhibitory effect on GSK-3β with IC50 value ranges between 4.68 ± 0.59 to 8.27 ± 0.60 nM compared to that of staurosporine (IC50 = 6.12 ± 0.74 nM). Considerably, compounds 7c, 7e and 7f effectively lowered tau hyperphosphorylated aggregates and proving their safety towards the SH-SY5Y and THLE2 normal cell lines. The most promising compound 7c alleviated cognitive impairments in the scopolamine-induced model in mice. Compound 7c's activity profile, while not highly selective, may provide a starting point and valuable insights into the design of multi-target inhibitors. According to the ADME prediction results, compounds 7c, 7e and 7f followed Lipinski's rule of five and could almost permeate through the BBB. Molecular docking simulations showed that these compounds are well accommodated in the ATP binding site interacting by its quinoline-2-one ring through hydrogen bonding with the key amino acids Asp133 and Val135 at the hinge region. The findings of this study suggested that these new compounds may have potential as anti-AD drugs targeting GSK-3β.

Synthesis, characterization, molecular modeling studies, and biological evaluation of metal piroxicam complexes (M = Ni(II), Pt(IV), Pd(II), Ag(I)) as antibacterial and anticancer agents

Four piroxicam metal complexes; NiL2 , PtL2 , PdL2 , and AgL were synthesized and characterized by different techniques with enhanced antibacterial and anticancer activity. Regarding in vitro antimicrobial activity, complex NiL2 displayed potent antibacterial effect against Escherichia coli and Pseudomonas aeruginosa that was 1.9-folds higher than piroxicam (minimum inhibitory concentration [MIC] = 31.85, 65.32 µM), respectively. In case of G+ve bacteria, complex PtL2 had potent activity on Staphylococcus aureus which was 2.1-folds higher than piroxicam (MIC = 43.12 µM), while activity of complex AgL against Enterococcus faecalis was threefolds higher than piroxicam (MIC = 74.57 µM. Complexes PtL2 and PdL2 exhibited higher inhibition of DNA gyrase than piroxicam (IC50  = 6.21 µM) in the range of 1.9-1.7-folds. The in vitro antiproliferative activity depicted that all investigated complexes showed better cytotoxic effect than piroxicam, specifically Pt and Pd complexes which had lower IC50 values than piroxicam on human liver cancer cell line HepG2 by 1.8 and 1.7-folds, respectively. While Pd and Ag complexes showed 2 and 1.6-folds better effect on human colon cancer cell line HT-29 compared with piroxicam. Molecular modeling studies including docking on Stranded DNA Duplex (1juu) and DNA gyrase enzyme (1kzn) that gave good insight about interaction of complexes with target molecules, calculation of electrostatic potential map and global reactivity descriptors were performed.

Conjugates of amiridine and thiouracil derivatives as effective inhibitors of butyrylcholinesterase with the potential to block β-amyloid aggregation

New amiridine-thiouracil conjugates with different substituents in the pyrimidine fragment (R = CH3 , CF2 Н, CF3 , (CF2 )2 H) and different spacer lengths (n = 1-3) were synthesized. The conjugates rather weakly inhibit acetylcholinesterase (AChE) and exhibit high inhibitory activity (IC50 up to 0.752 ± 0.021 µM) and selectivity to butyrylcholinesterase (BChE), which increases with spacer elongation; the lead compounds are 11c, 12c, and 13c. The conjugates are mixed-type reversible inhibitors of both cholinesterases and practically do not inhibit the structurally related off-target enzyme carboxylesterase. The results of molecular docking to AChE and BChE are consistent with the experiment on enzyme inhibition and explain the structure-activity relationships, including the rather low anti-AChE activity and the high anti-BChE activity of long-chain conjugates. The lead compounds displace propidium from the AChE peripheral anion site (PAS) at the level of the reference compound donepezil, which agrees with the mixed-type mechanism of AChE inhibition and the main mode of binding of conjugates in the active site of AChE due to the interaction of the pyrimidine moiety with the PAS. This indicates the ability of the studied conjugates to block AChE-induced aggregation of β-amyloid, thereby exerting a disease-modifying effect. According to computer calculations, all synthesized conjugates have an ADME profile acceptable for drugs.

Piperazine-2-carboxylic acid derivatives as MTDLs anti-Alzheimer agents: Anticholinesterase activity, mechanistic aspect, and molecular modeling studies

Development of Multitarget-Directed Ligands (MTDLs) is a promising approach to combat the complex etiologies of Alzheimer's disease (AD). Herein we report the design, synthesis, and characterization of a new series of 1,4-bisbenzylpiperazine-2-carboxylic acid derivatives 3-5(a-g), 7a-f, 8a-s, and their piperazine-2-yl-1,3,4-oxadiazole analogs 6a-g. In vitro inhibitory effect against Electrophorus electricus acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) from Equine serum was evaluated using modified Ellman's method, considering donepezil and tacrine as reference drugs. Lineweaver-Burk plot analysis of the results proved competitive inhibition of AChE and BChE with Ki values, in low micromolar range. The free carboxylic acid series 4a-g showed enhanced selectivity for AChE. Hence, 4c, 1,4-bis (4-chlorobenzyl)-piperazinyl-2-carboxylic acid), was the most active member of this series (Ki (AChE) = 10.18 ± 1.00 µM) with clear selectivity for AChE (SI ∼ 17.90). However, the hydroxamic acids 7a-f and carboxamides 8a-s congeners were more potent and selective inhibitors of BChE (SI ∼ 5.38 - 21862.5). Extraordinarily, 1,4-bis (2-chlorobenzyl)-piperazinyl-2-hydroxamic acid 7b showed promising inhibitory activity against BChE enzyme (Ki = 1.6 ± 0.08 nM, SI = 21862.5), that was significantly superior to that elicited by donepezil (Ki = 12.5 ± 2.6 µM) and tacrine (Ki = 17.3 ± 2.3 nM). Cytotoxicity assessment of 4c and 7b, on human neuroblastoma (SH-SY5Y) cell lines, revealed lower toxicity than staurosporine and was nearly comparable to that of donepezil. Molecular docking and molecular dynamics simulation afforded unblemished insights into the structure-activity relationships for AChE and BChE inhibition. The results showed stable binding with fair H-bonding, hydrophobic and/or ionic interactions to the catalytic and peripheral anionic sites of the enzymes. In silico predicted ADME and physicochemical properties of conjugates showed good CNS bioavailability and safety parameters. In this regard, compound (7b) might be considered as a promising inhibitor of BChE with an innovative donepezil-based anti-Alzheimer activity. Further assessments of the most potent AChE and BChE inhibitors as potential MTDLs anti-Alzheimer's agents are under investigation with our research group and will be published later.

N4-Substituted Piperazinyl Norfloxacin Derivatives with Broad-Spectrum Activity and Multiple Mechanisms on Gyrase, Topoisomerase IV, and Bacterial Cell Wall Synthesis

Fluoroquinolones are an important class of antibiotics with broad-spectrum antibacterial and antitubercular activity. Here, we describe the design and synthesis of a series of 38 N4-substituted piperazinyl norfloxacin derivatives. Their activity and mechanism of action were characterized using in silico, in vitro, and in vivo approaches. Several compounds displayed interesting activities against both Gram-negative and Gram-positive bacteria, and few displayed antimycobacterial activity, whereby some were as potent as norfloxacin and ciprofloxacin. Molecular docking experiments suggested that the new derivatives inhibit both DNA gyrase and DNA topoisomerase IV in a similar manner as norfloxacin. Selecting the most promising candidates for experimental mode of action analysis, we confirmed DNA gyrase and topoisomerase IV as targets of all tested compounds using enzymatic in vitro assays. Phenotypic analysis of both Escherichia coli and Bacillus subtilis confirmed a typical gyrase inhibition phenotype for all of the tested compounds. Assessment of possible additional targets revealed three compounds with unique effects on the B. subtilis cell wall synthesis machinery, suggesting that they may have an additional target in this pathway. Comparison with known cell wall synthesis inhibitors showed that the new compounds elicit a distinct and, so far, unique phenotype, suggesting that they act differently from known cell wall synthesis inhibitors. Interestingly, our phenotypic analysis revealed that both norfloxacin and ciprofloxacin displayed additional cellular effects as well, which may be indicative of the so far unknown additional mechanisms of fluoroquinolones.

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

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

Multitargeted C9-substituted ester and ether derivatives of berberrubine for Alzheimer's disease: Design, synthesis, biological evaluation, metabolic stability, and pharmacokinetics

Berberrubine is a naturally occurring isoquinoline alkaloid and a bioactive metabolite of berberine. Berberine exhibits a wide range of pharmacological activities, including cholinesterase inhibition. The cholinesterase inhibitors provide symptomatic treatment for Alzheimer's disease; however, multitarget-directed ligands have the potential as disease-modifying therapeutics. Herein, we prepared a series of C9-substituted berberrubine derivatives intending to discover dual cholinesterase and beta-site amyloid-precursor protein cleaving enzyme 1 (BACE-1) inhibitors. Most synthesized derivatives possessed balanced dual inhibition (AChE and BChE) activity in the submicromolar range and a moderate inhibition against BACE-1. Two most active ester derivatives, 12a and 11d, display inhibition of AChE, BChE, and BACE-1. The 3-methoxybenzoyl ester derivative, 12a, inhibits electric eel acetylcholinesterase (EeAChE), equine serum butyrylcholinesterase (eqBChE), and human hBACE-1 with IC₅₀ values of 0.5, 4.3, and 11.9 μM, respectively and excellent BBB permeability (P_e  = 8 × 10^-6  cm/s). The ester derivative 12a is metabolically unstable; however, its ether analog 13 is stable in HLM and exhibits inhibition of AChE, BChE, and BACE-1 with IC₅₀ values of 0.44, 3.8, and 17.9 μM, respectively. The ether analog also inhibits self-aggregation of Aβ and crosses BBB (P_e  = 7.3 × 10^-6  cm/s). Administration of 13 at 5 mg/kg (iv) in Wistar rats showed excellent plasma exposure with AUC_0-∞ of 28,834 ng min/ml. In conclusion, the multitargeted berberrubine ether derivative 13 is CNS permeable and has good ADME properties.

Current Pharmacotherapy and Multi-Target Approaches for Alzheimer's Disease

Alzheimer's disease (AD) is a neurodegenerative disorder characterized by decreased synaptic transmission and cerebral atrophy with appearance of amyloid plaques and neurofibrillary tangles. Cognitive, functional, and behavioral alterations are commonly associated with the disease. Different pathophysiological pathways of AD have been proposed, some of which interact and influence one another. Current treatment for AD mainly involves the use of therapeutic agents to alleviate the symptoms in AD patients. The conventional single-target treatment approaches do not often cause the desired effect in the disease due to its multifactorial origin. Thus, multi-target strategies have since been undertaken, which aim to simultaneously target multiple targets involved in the development of AD. In this review, we provide an overview of the pathogenesis of AD and the current drug therapies for the disease. Additionally, rationales of the multi-target approaches and examples of multi-target drugs with pharmacological actions against AD are also discussed.

Toll-Like Receptor 4: A Promising Therapeutic Target for Alzheimer's Disease

Alzheimer's disease (AD) is a progressive neurodegenerative disease that primarily manifests as memory deficits and cognitive impairment and has created health challenges for patients and society. In AD, amyloid β-protein (Aβ) induces Toll-like receptor 4 (TLR4) activation in microglia. Activation of TLR4 induces downstream signaling pathways and promotes the generation of proinflammatory cytokines, such as tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), and interleukin-1β (IL-1β), which also trigger the activation of astrocytes and influence amyloid-dependent neuronal death. Therefore, TLR4 may be an important molecular target for treating AD by regulating neuroinflammation. Moreover, TLR4 regulates apoptosis, autophagy, and gut microbiota and is closely related to AD. This article reviews the role of TLR4 in the pathogenesis of AD and a range of potential therapies targeting TLR4 for AD. Elucidating the regulatory mechanism of TLR4 in AD may provide valuable clues for developing new therapeutic strategies for AD.

Development of spiro-3-indolin-2-one containing compounds of antiproliferative and anti-SARS-CoV-2 properties

A series of 1″-(alkylsulfonyl)-dispiro[indoline-3,2'-pyrrolidine-3',3″-piperidine]-2,4″-diones 6a‒o has been synthesized through regioselective multi-component azomethine dipolar cycloaddition reaction of 1-(alkylsulfonyl)-3,5-bis(ylidene)-piperidin-4-ones 3a‒h. X-ray diffraction studies (6b‒d,h) confirmed the structures. The majority of the synthesized analogs reveal promising antiproliferation properties against a variety of human cancer cell lines (MCF7, HCT116, A431 and PaCa2) with good selectivity index towards normal cell (RPE1). Some of the synthesized agents exhibit potent inhibitory properties against the tested cell lines with higher efficacies than the standard references (sunitinib and 5-fluorouracil). Compound 6m is the most potent. Multi-targeted inhibitory properties against EGFR and VEGFR-2 have been observed for the synthesized agents. Flow cytometry supports the antiproliferation properties and shows the tested agents as apoptosis and necrosis forming. Vero cell viral infection model demonstrates the anti-SARS-CoV-2 properties of the synthesized agents. Compound 6f is the most promising (about 3.3 and 4.8 times the potency of the standard references, chloroquine and hydroxychloroquine). QSAR models explain and support the observed biological properties.

Novel thiophene Chalcones-Coumarin as acetylcholinesterase inhibitors: Design, synthesis, biological evaluation, molecular docking, ADMET prediction and molecular dynamics simulation

A series of around eight novel chalcone based coumarin derivatives (23a-h) was designed, subjected to in-silico ADMET prediction, synthesized, characterized by IR, NMR, Mass analytical techniques and evaluated as acetylcholinesterase (AChE) inhibitor for the treatment of Alzheimer's disease (AD). The results of predicted ADMET study demonstrated the drug-likeness properties of the titled compounds with developmental challenges in lipophilicity and solubility parameters. The in vitro assessment of the synthesized compounds revealed that all of them showed significant activity (IC₅₀ ranging from 0.42 to 1.296 µM) towards AChE compared to the standard drug, galantamine (IC₅₀ = 1.142 ± 0.027 µM). Among these, compound 23e displayed the most potent inhibitory activity with IC₅₀ value of 0.42 ± 0.019 µM. Cytotoxicity of all compounds was tested on normal human hepatic (THLE-2) cell lines at three different concentrations using the MTT assay, in which none of the compound showed significant toxicity at the highest concentration of 1000 µg/ml compared to the control group. Based on the docking study against AChE, the most active derivative 23e was orientated towards the active site and occupied both catalytic anionic site (CAS) and peripheral anionic site (PAS) of the target enzyme. In-silico studies revealed tested showed better inhibition activity of AChE compared to Butyrylcholinesterase (BuChE). Molecular dynamics simulation explored the stability and dynamic behavior of 23e- AChE complex.

The novel therapeutic strategy of vilazodone-donepezil chimeras as potent triple-target ligands for the potential treatment of Alzheimer's disease with comorbid depression

Depression is one of the most frequent comorbid psychiatric symptoms of Alzheimer's disease (AD), and no efficacious drugs have been approved specifically for this purpose thus far. Herein, we proposed a novel therapeutic strategy that merged the key pharmacophores of the antidepressant vilazodone (5-HT_1A receptor partial agonist and serotonin transporter inhibitor) and the anti-AD drug donepezil (acetylcholinesterase inhibitor) together to develop a series of multi-target-directed ligands for potential therapy of the comorbidity of AD and depression. Accordingly, 55 vilazodone-donepezil chimeric derivatives were designed and synthesized, and their triple-target activities against acetylcholinesterase, 5-HT_1A receptor, and serotonin transporter were systematically evaluated. Among them, compound 5 displayed strong triple-target bioactivities in vitro, low hERG potassium channel inhibition and acceptable brain distribution. Importantly, oral intake of 5 mg/kg of the compound 5 dihydrochloride significantly alleviated the depressive symptoms and ameliorated cognitive dysfunction in mouse models. In brief, these results highlight vilazodone-donepezil chimeras as a prospective therapeutic approach for the treatment of the comorbidity of AD and depression.

Strategies for Structural Modification of Small Molecules to Improve Blood-Brain Barrier Penetration: A Recent Perspective

In the development of central nervous system (CNS) drugs, the blood-brain barrier (BBB) restricts many drugs from entering the brain to exert therapeutic effects. Although many novel delivery methods of large molecule drugs have been designed to assist transport, small molecule drugs account for the vast majority of the CNS drugs used clinically. From this perspective, we review studies from the past five years that have sought to modify small molecules to increase brain exposure. Medicinal chemists make it easier for small molecules to cross the BBB by improving diffusion, reducing efflux, and activating carrier transporters. On the basis of their excellent work, we summarize strategies for structural modification of small molecules to improve BBB penetration. These strategies are expected to provide a reference for the future development of small molecule CNS drugs.

Structural exploration of multifunctional monoamine oxidase B inhibitors as potential drug candidates against Alzheimer's disease

AD is one of the most typical neurodegenerative disorders that suffer many seniors worldwide. Recently, MAO inhibitors have received increasing attention not only for their roles involved in monoamine neurotransmitters metabolism and oxidative stress but also for their additional neuroprotective and neurorescue effects against AD. The curiosity in MAO inhibitors is reviving, and novel MAO-B inhibitors recently developed with ancillary activities (e.g., Aβ aggregation and AChE inhibition, anti-ROS and chelating activities) have been proposed as multitarget drugs foreshadowing a positive outlook for the treatment of AD. The current review describes the recent development of the design, synthesis, and screening of multifunctional ligands based on MAO-B inhibition for AD therapy. Structure-activity relationships and rational design strategies of the synthetic or natural product derivatives (chalcones, coumarins, chromones, and homoisoflavonoids) are discussed.

Sulfur-containing therapeutics in the treatment of Alzheimer's disease

Sulfur is widely existent in natural products and synthetic organic compounds as organosulfur, which are often associated with a multitude of biological activities. OBenzothiazole, in which benzene ring is fused to the 4,5-positions of the thiazolerganosulfur compounds continue to garner increasing amounts of attention in the field of medicinal chemistry, especially in the development of therapeutic agents for Alzheimer's disease (AD). AD is a fatal neurodegenerative disease and the primary cause of age-related dementia posing severe societal and economic burdens. Unfortunately, there is no cure for AD. A lot of research has been conducted on sulfur-containing compounds in the context of AD due to their innate antioxidant potential and some are currently being evaluated in clinical trials. In this review, we have described emerging trends in the field, particularly the concept of multi-targeting and formulation of disease-modifying strategies. SAR, pharmacological targets, in vitro/vivo ADMET, efficacy in AD animal models, and applications in clinical trials of such sulfur compounds have also been discussed. This article provides a comprehensive review of organosulfur-based AD therapeutic agents and provides insights into their future development.

Biological evaluation of 7-O-amide hesperetin derivatives as multitarget-directed ligands for the treatment of Alzheimer's disease

A series of 7-O-amide hesperetin derivatives were subjected to multi-target biological evaluation of anti-Alzheimer's disease. Most of the compounds showed good in vitro inhibitory activity against cholinesterase, of which compound 7c (7-O-(4-(morpholinoethyl)-acetamide) hesperetin) was the most effective anti-eqBuChE derivative (IC₅₀ = 0.28 ± 0.05 μM) and exerted neuroprotective effects. Further biological evaluation found that compounds 4d, 4e and 7c showed strong antioxidant, anti-Aβ self-aggregation and anti-neuroinflammatory activities. Compound 7c could inhibit the expression of iNOS and COX-2 proteins and prevent LPS-induced inflammatory response in BV2 cells. In addition, compound 7c could chelate biometal ions such as Cu²⁺ and Zn²⁺. In the vivo study, the MWM test confirmed that compound 7c could improve the cognitive impairment caused by scopolamine. In summary, the above studies have shown that the optimized compound 7c has great development potential as MTDL for the treatment of AD.

In silico modeling for dual inhibition of acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) enzymes in Alzheimer's disease

In this research, we have implemented two-dimensional quantitative structure-activity relationship (2D-QSAR) modeling using two different datasets, namely, acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) enzyme inhibitors. A third dataset has been derived based on their selectivity and used for the development of partial least squares (PLS) based regression models. The developed models were extensively validated using various internal and external validation parameters. The features appearing in the model against AChE enzyme suggest that a small ring size, higher number of -CH2- groups, higher number of secondary aromatic amines and higher number of aromatic ketone groups may contribute to the inhibitory activity. The features obtained from the model against BuChE enzyme suggest that the sum of topological distances between two nitrogen atoms, higher number of fragments X-C(=X)-X, higher number of secondary aromatic amides, fragment R--CR-X may be more favorable for inhibition. The features obtained from selectivity based model suggest that the number of aromatic ethers, unsaturation content relative to the molecular size and molecular shape may be more specific for the inhibition of the AChE enzyme in comparison to the BuChE enzyme. Moreover, we have implemented the molecular docking studies using the most and least active molecules from the datasets in order to identify the binding pattern between ligand and target enzyme. The obtained information is then correlated with the essential structural features associated with the 2D-QSAR models.

Perspectives for New and More Efficient Multifunctional Ligands for Alzheimer's Disease Therapy

Despite tremendous research efforts at every level, globally, there is still a lack of effective drugs for the treatment of Alzheimer's disease (AD). The biochemical mechanisms of this devastating neurodegenerative disease are not yet clearly understood. This review analyses the relevance of multiple ligands in drug discovery for AD as a versatile toolbox for a polypharmacological approach to AD. Herein, we highlight major targets associated with AD, ranging from acetylcholine esterase (AChE), beta-site amyloid precursor protein cleaving enzyme 1 (BACE-1), glycogen synthase kinase 3 beta (GSK-3β), N-methyl-d-aspartate (NMDA) receptor, monoamine oxidases (MAOs), metal ions in the brain, 5-hydroxytryptamine (5-HT) receptors, the third subtype of histamine receptor (H3 receptor), to phosphodiesterases (PDEs), along with a summary of their respective relationship to the disease network. In addition, a multitarget strategy for AD is presented, based on reported milestones in this area and the recent progress that has been achieved with multitargeted-directed ligands (MTDLs). Finally, the latest publications referencing the enlarged panel of new biological targets for AD related to the microglia are highlighted. However, the question of how to find meaningful combinations of targets for an MTDLs approach remains unanswered.

Synthesis and molecular modeling studies of cholinesterase inhibitor dispiro[indoline-3,2'-pyrrolidine-3',3''-pyrrolidines]

A set of dispiro[indoline-3,2′-pyrrolidine-3′,3′′-pyrrolidines] 8a–l was regioselectively synthesized utilizing multi-component azomethine cycloaddition reaction of 3-(arylmethylidene)pyrrolidine-2,5-diones 5a–e, isatins 6a–c and sarcosine 7. Single crystal X-ray studies of 8c add conclusive support for the structure. Compounds 8e and 8g reveal cholinesterase inhibitory properties with promising efficacy against both AChE and BChE and were found to be more selective towards AChE than BChE as indicted by the selectivity index like Donepezil (a clinically used cholinesterase inhibitory drug). Molecular modeling studies assist in understanding the bio-observations and identifying the responsible parameters behind biological properties.

Dispiro[indoline-3,2′-pyrrolidine-3′,3′′-pyrrolidines] were regioselectively synthesized revealing cholinesterase (AChE, BChE) inhibitory properties.

Circumdatin D Exerts Neuroprotective Effects by Attenuating LPS-Induced Pro-Inflammatory Responses and Downregulating Acetylcholinesterase Activity In Vitro and In Vivo

Alzheimer's disease (AD) is a prevalent neurodegenerative disorder with multifactorial causes, of which systemic inflammation may play a key role to promote neurodegeneration, and acetylcholinesterase (AChE) is a target protein to induce cholinergic transmission. Inhibitors toward inflammation and targeting AChE are regarded to promote cholinergic signaling of the central nervous system in AD therapy. During the search for neuroprotection agents from marine-derived compounds, seven circumdatin-type alkaloids from a coral-associated fungus Aspergillus ochraceus LZDX-32-15 showed potent inhibition against lipopolysaccharide (LPS)-induced nitric oxide (NO) production and activation of NF-κB report gene along with anti-AChE activities. Among the tested compounds, circumdatin D showed the most potent inhibitory effect against AChE activity and NO production. In vivo experiments using AD-like nematode models demonstrated that circumdatin D effectively delayed paralysis of CL4176 worms upon temperature up-shift via suppression of AChE activity and inflammatory-related gene expression. Moreover, circumdatin D interfered with inflammatory response by inhibiting the secretion of pro-inflammatory cytokines in LPS-induced BV-2 and primary microglia cells. Mechanistically, circumdatin D modulated Toll-like receptor 4 (TLR4)-mediated NF-κB, MAPKs and JAK/STAT inflammatory pathways in LPS-stimulated BV-2 cells, and protected primary neurons cells from LPS-induced neurotoxicity. Thus, circumdatin D is a potential agent for neuroprotective effects by the multi-target strategy.

Discovery of nitazoxanide-based derivatives as autophagy activators for the treatment of Alzheimer's disease

Drug repurposing is an efficient strategy for new drug discovery. Our latest study found that nitazoxanide (NTZ), an approved anti-parasite drug, was an autophagy activator and could alleviate the symptom of Alzheimer's disease (AD). In order to further improve the efficacy and discover new chemical entities, a series of NTZ-based derivatives were designed, synthesized, and evaluated as autophagy activator against AD. All compounds were screened by the inhibition of phosphorylation of p70S6K, which was the direct substrate of mammalian target of rapamycin (mTOR) and its phosphorylation level could reflect the mTOR-dependent autophagy level. Among these analogs, compound 22 exhibited excellent potency in promoting β-amyloid (Aβ) clearance, inhibiting tau phosphorylation, as well as stimulating autophagy both in vitro and in vivo. What's more, 22 could effectively improve the memory and cognitive impairments in APP/PS1 transgenic AD model mice. These results demonstrated that 22 was a potential candidate for the treatment of AD.

The development of advanced structural framework as multi-target-directed ligands for the treatment of Alzheimer's disease

In this work, we have developed a novel series of multi-target-directed ligands to address low levels of acetylcholine (ACh), oxidative stress, metal ion dysregulation, and the misfolded proteins. Novel apigenin-donepezil derivatives, naringenin-donepezil derivatives, genistein-donepezil derivatives and chalcone-donepezil derivatives have been synthesized, in vitro results showed that TM-4 was a reversible and potent huAChE (IC₅₀ = 0.36 μM) and huBChE (IC₅₀ = 15.3 μM) inhibitor, and showed potent antioxidant activity (ORAC = 1.2 eq). TM-4 could significantly inhibit self-induced Aβ_1-42 aggregation (IC₅₀ = 3.7 μM). TM-4 was also an ideal neuroprotectant, potential metal chelation agent, and it could inhibit and disaggregate huAChE-induced and Cu²⁺-induced Aβ aggregation. Moreover, TM-4 could activate UPS degradation pathway in HT22 cells and induce autophagy on U87 cells to clear abnormal proteins associated with AD. More importantly, TM-4 could cross BBB in vitro assay. In addition, in vivo assay revealed that TM-4 exhibited remarkable dyskinesia recovery rate and response efficiency on AlCl₃-induced zebrafish AD model, and TM-4 indicated surprising protective effect on Aβ_1-40-induced vascular injury. TM-4 presented precognitive effect on scopolamine-induced memory impairment. And the regulation of multi-targets for TM-4 were further conformed through transcriptome sequencing. More interesting, the blood, urine and feces metabolism in rat and rat/human liver microsome metabolism towards TM-4 were also investigated. Overall, TM-4 is a promising multi-function candidate for the development of drugs to Alzheimer's disease.

Structurally Related Edaravone Analogues: Synthesis, Antiradical, Antioxidant, and Copper-Chelating Properties

Background::

The current therapeutic options available to patients diagnosed with Amyotrophic Lateral Sclerosis (ALS) are limited and edaravone is a compound that has gained significant interest for its therapeutic potential in this condition.

Objectives: :

The current work was thus undertaken to synthesize and characterize a series of edaravone analogues.

Methods:

A total of 17 analogues were synthesized and characterized for their antioxidant properties, radical scavenging potential and copper-chelating capabilities.

Results:

Radical scavenging and copper-chelating properties were notably observed for edaravone. Analogues bearing hydrogen in position 1 and a phenyl at position 3 and a phenyl in both positions of pyrazol-5 (4H)-one displayed substantial radical scavenging, antioxidants and copper-chelating properties. High accessibility of electronegative groups combined with higher electronegativity and partial charge of the carbonyl moiety in edaravone might explain the observed difference in the activity of edaravone relative to the closely related analogues 6 and 7 bearing hydrogen at position 1 and a phenyl at position 3 (6) and a phenyl in both positions (7).

Conclusion:

Overall, this study reveals a subset of edaravone analogues with interesting properties. Further investigation of these compounds is foreseen in relevant models of oxidative stress-associated diseases in order to assess their therapeutic potential in such conditions.

Aryldiazoquinoline based multifunctional small molecules for modulating Aβ42aggregation and cholinesterase activity related to Alzheimer's disease

Novel series of aryldiazoquinoline multifunctional molecules controls amyloid formation and neuro-protective role by inhibiting esterase enzymes.

New phosphazine and phosphazide derivatives as multifunctional ligands targeting acetylcholinesterase and β-Amyloid aggregation for treatment of Alzheimer's disease

Phosphazine and phosphazide derivatives are described herein as a new class of selective and potent acetylcholinesterase (AChE) inhibitors and β-amyloid aggregation inhibitors. Phosphazines (5-7) were synthesized smoothly via a redox-condensation reaction of 1,2-bis(diphenylphosphino)ethane with different amines derivatives in the presence of dialkyl azodicarboxylate (Staudinger reaction) while phosphazides (8) via electrophilic attack of azido derivatives. Structures of the synthesized compounds were justified on the basis of compatible elementary and spectroscopic analyses. All the compounds were evaluated for their acetylcholinesterase inhibitory activity. The most three potent compounds (5b-c and 8b) showing AChE IC₅₀ values (29.85-34.96 nM) comparable to that of donepezil (34.42 nM) were subjected to further investigation by testing their butyrylcholinesterase, MMP-2 and self-induced Aβ aggregation inhibition activity. Especially, the coumarin phosphazide derivative (8b) presented the best AChE inhibition selectivity index (IC₅₀ = 34.96 nM, AChE/BuChE; 3.81) together with good inhibition ability against MMP-2 (IC₅₀ = 441.33 nM) and self-induced Aβ_1-42 aggregation (IC₅₀ = 337.77 nM). In addition, the inhibition of metal-induced Aβ aggregation by 8b was confirmed by thioflavine T fluorescence. The most potent effect of 8b was observed on the Zn²⁺-induced Aβ₄₂ aggregation. Kinetic study of compound 8b suggested it to be a competitive AChE inhibitor. Also, it specifically chelates metal and is predicted to be permeable to BBB. It also possesses low toxicity on SH-SY5Y neuroblastoma cells with a safety index of 15.37. In addition, it was demonstrated that compound 8b can improve the cognitive impairment of scopolamine-induced model in mice with % alternations and transfer latency time comparable to that of donepezil. Also, a docking study was carried out and it was in accordance with the in vitro results. These promising in vitro and in vivo findings highlight compound 8b as a possible drug candidate in searching for new multifunctional AD drugs.

CH(II), a cerebroprotein hydrolysate, exhibits potential neuro-protective effect on Alzheimer's disease

Alzheimer's disease (AD) is a progressive neurodegenerative disorder, and is the most common type of cognitive impairment and dementia. There is a pressing need to improve the clinical efficacy and quality of life for AD patients, as limited treatments options for AD patients have been developed until now. In this study, we aim to investigate the protective effect of CH(II), a cerebroprotein hydrolysate consisted of abundant biological peptides, on preclinical model of AD. We found that CH(II) treatment effectively protects oxygen glucose deprivation (OGD)-induced N2A cell viability impairment and cell apoptosis. In addition, CH(II) significantly reduces H2O2-induced ROS accumulation and exhibits the protective activities against H2O2-induced oxidative injury. Intriguingly, we found that CH(II) treatment can effectively promote neurite outgrowth of N2A cells. Moreover, CH(II) obviously improve the cognitive and memorial function in scopolamine-induced amnesia mice model. Taken together, this study provides evidences of the neuroprotective activities of CH(II) and offers a potential therapeutic strategy for AD patients.

Targeting virulence factors as an antimicrobial approach: Pigment inhibitors

The fascinating and dangerous colored pathogens contain unique chemically pigmented molecules, which give varied and efficient assistance as virulence factors to the crucial reproduction and growth of microbes. Therefore, multiple novel strategies and inhibitors have been developed in recent years that target virulence factor pigments. However, despite the importance and significance of this topic, it has not yet been comprehensively reviewed. Moreover, research groups around the world have made successful progress against antibacterial infections by targeting pigment production, including our serial works on the discovery of CrtN inhibitors against staphyloxanthin production in Staphylococcus aureus. On the basis of the previous achievements and recent progress of our group in this field, this article will be the first comprehensive review of pigment inhibitors against colored pathogens, especially S. aureus infections, and this article includes design strategies, representative case studies, advantages, limitations, and perspectives to guide future research.

Novel chromanone-dithiocarbamate hybrids as multifunctional AChE inhibitors with β-amyloid anti-aggregation properties for the treatment of Alzheimer's disease

By connecting chromanone with dithiocarbamate moieties through flexible linkers, a series of hybrids as novel multifunctional AChE inhibitors have been designed and synthesized. Most of these compounds displayed strong and excellently selective inhibition to eeAChE as well as potent inhibition to self- and AChE-induced Aβ aggregation. Among them, compound 6c showed the best activity to inhibit eeAChE (IC₅₀ = 0.10 μM) and AChE-induced Aβ aggregation (33.02% at 100 μM), and could effectively inhibit self-induced Aβ aggregation (38.25% at 25 μM). Kinetic analysis and docking study indicated that compound 6c could target both the CAS and PAS, suggesting that it was a dual binding site inhibitor for AChE. Besides, it exhibited good ability to penetrate the BBB and low neurotoxicity in SH-SY5Y cells. More importantly, compound 6c was well tolerated in mice (2500 mg/kg, po) and could attenuate the memory impairment in a scopolamine-induced mouse model. Overall, these results highlight 6c as a promising multifunctional agent for treating AD and also demonstrate that the dithiocarbamate is a valid scaffold for design of multifunctional AChE inhibitors.

Pharmacological investigation of quinoxaline-bisthiazoles as multitarget-directed ligands for the treatment of Alzheimer's disease

Alzheimer's disease (AD) is the most prevalent disease of old age leading to dementia. Complex AD pathogenesis involves multiple factors viz. amyloid plaque formation, neurofibrillary tangles and inflammation. Herein we report of a new series of quinoxaline-bisthiazoles as multitarget-directed ligands (MTDLs) targeting BACE-1 and inflammation concurrently. Virtual screening of a library of novel quinoxaline-bisthiazoles was performed by docking studies. The most active molecules from the docking library were taken up for synthesis and characterized by spectral data. Compounds 8a-8n showed BACE-1 inhibition in micro molar range. One of the compounds, 8n showed BACE-1 inhibition at IC₅₀ of 3 ± 0.07 µM. Rat paw edema inhibition in acute and chronic models of inflammation were obtained at 69 ± 0.45% and 55 ± 0.7%, respectively. Compound 8n also showed noteworthy results in AlCl₃ induced AD model. The treated rats exhibited excellent antiamnesic, antiamyloid, antioxidant, and neuroprotective properties. Behavioural parameters suggested improved cognitive functions which further validates the testimony of present study. Moreover, compound 8n was found to have inherent gastrointestinal safety. This new string of quinoxaline-bisthiazoles were identified as effective lead for the generation of potent MTDLs and compound 8n was found to showcase qualities to tackle AD pathogenesis.

Reconsideration of Anticholinesterase Therapeutic Strategies against Alzheimer's Disease

Alzheimer's disease (AD) is well-known as a severe neurodegeneration disease involving complicated etiologies, and cholinesterase inhibition remain the prevailing mode of clinical intervention in AD management. Although most clinically applied cholinesterase inhibitors (ChEIs) achieve limited clinical outcomes, research on the central cholinergic system is still thriving. Recently, an impressive amount of knowledge regarding novel acetylcholinesterase functions, as well as the close association between the central cholinergic system and other key elements for AD pathogenesis, has accumulated, highlighting that this field still has great potential for future drug development. In contrast to the overwhelmingly disappointing clinical therapeutic effects of various disease-modifying drug candidates, interesting evidence has continued to emerge over the past 20 years from the wealth of preclinical and clinical data on the usage of ChEIs, indicating underestimated clinical benefits due to physician ambivalence, a lack of persistent treatment, and inappropriate medication times or doses. Here we pinpoint several topics fit for future attention, focusing on the updated cholinergic hypothesis, especially the pleiotropic relationships with key pathogenetic signaling pathways and functions in AD, as well as possible novel therapeutic strategies, including novel ChEIs and cholinesterase inhibition-based innovative multifunctional therapeutic candidates. We intend to strengthen the future value of the precise application of cholinergic drugs, especially novel ChEIs, as a cornerstone pharmacological approach to AD treatment, either alone or in combination with other targets, to relieve symptoms and to modify disease progression.

Rational Design of Novel Selective Dual-Target Inhibitors of Acetylcholinesterase and Monoamine Oxidase B as Potential Anti-Alzheimer's Disease Agents

Multifunctional agents aiming at cholinesterases (ChEs) and monoamine oxidases (MAOs) are promising therapy for Alzheimer's disease (AD). Herein, a series of novel propargylamine-modified pyrimidinylthiourea derivatives (1-4) were designed and synthesized as dual inhibitors of ChEs and MAOs with other functions against AD. Most of these derivatives inhibited ChEs and MAOs with IC₅₀ values in the micro- or nanomolar ranges. Compound 1c displayed the dual functional profile of targeting the AChE (IC₅₀ = 0.032 ± 0.007 μM) and MAO-B (IC₅₀ = 2.117 ± 0.061 μM), along with the improved blood-brain barrier (BBB) permeability, antioxidant ability, and good copper chelating property in vitro. Animal studies showed that compound 1c·HCl could inhibit the cerebral AChE/MAO-B activities and alleviate scopolamine-induced cognitive impairment in mice. Combined with good oral bioavailability ( F = 45.55%), these findings demonstrated that compound 1c may be a potent brain permeable multifunctional candidate for the treatment of AD.

Carnosine-LVFFARK-NH2 Conjugate: A Moderate Chelator but Potent Inhibitor of Cu2+-Mediated Amyloid β-Protein Aggregation

Aggregation of amyloid-β (Aβ) protein stimulated by Cu²⁺ has been recognized as a crucial step in the neurodegenerative process of Alzheimer's disease. Hence, it is of significance to develop bifunctional agents capable of inhibiting Aβ aggregation as well as Cu²⁺-mediated Aβ toxicity. Herein, a novel bifunctional nonapeptide, carnosine-LVFFARK-NH₂ ( Car-LK7), was proposed by integrating native chelator carnosine ( Car) and an Aβ aggregation inhibitor, Ac-LVFFARK-NH₂ (LK7). Results revealed the bifunctionality of Car-LK7, including remarkably enhanced inhibition capability on Aβ aggregation as compared to LK7 and a moderate Cu²⁺ chelating affinity ( K_D = 28.2 ± 2.1 μM) in comparison to the binding affinity for Aβ₄₀ ( K_D = 1.02 ± 0.13 μM). The moderate Cu²⁺ affinity was insufficient for Car-LK7 to sequester Cu²⁺ from Aβ₄₀-Cu²⁺ species, but it was sufficient to form ternary Aβ₄₀-Cu²⁺- Car-LK7 complexes. Formation of the ternary complexes directed the aggregation into small, unstructured aggregates with little β-sheet structure. Car-LK7 also showed higher activity on arresting Aβ₄₀-Cu²⁺-catalyzed reactive oxygen species production than Car. Cell viability assays confirmed the prominent protection activity of Car-LK7 against Cu²⁺-mediated Aβ₄₀ cytotoxicity; Car-LK7 could almost eliminate Aβ₄₀ cytotoxicity at an equimolar dose (cell viability increased from 59% to 99%). The research has thus provided new insight into the design of potent bifunctional agents against metal-mediated amyloid toxicity by conjugating moderate metal chelators and existing inhibitors.