Phenoxyethyl Piperidine/Morpholine Derivatives as PAS and CAS Inhibitors of Cholinesterases: Insights for Future Drug Design

Carvacrol/thymol derivatives as highly selective BuChE inhibitors with anti-inflammatory activities: Discovery and bio-evaluation

In this study, nine novel carvacrol/thymol derivatives incorporating carbamate groups were designed, synthesized, and evaluated as multifunctional anti-AD agents. These derivatives displayed superior BuChE inhibitory and anti-inflammatory characteristics compared to the parent compounds. While the derivatives exhibited AChE IC50 values exceeding the detectable limit (>100 μM), they demonstrated high potency as BuChE inhibitors, with IC50 values ranging from 0.05 to 9.62 μM. In an inflammation model of BV2 microglial cells induced by lipopolysaccharide (LPS), the derivatives effectively reduced the levels of the pro-inflammatory cytokine interleukin-1β (IL1β), with inhibition rates of IL1β exceeding 50 % at 10 μM. Notably, compound SXF3 ‌attained the highest BuChE inhibition efficacy (eqBuChE IC50 = 0.05 ± 0.003 μM, hBuChE IC50 = 0.04 ± 0.001 μM), the highest selectivity for BuChE (with a selectivity index, SI, exceeding 2000, calculated as the ratio of eeAChE IC50 to eqBuChE IC50) and high anti-inflammatory activity (inhibition of IL1β, IC50 = 8.33 ± 0.08 μM). In a scopolamine-induced AD mouse model, SXF3 (15 mg/kg) significantly reduced the latency to the platform and attenuated memory deficits. Biochemical analysis confirmed that SXF3 significantly increased acetylcholine (ACh) levels in the mice hippocampus, primarily due to the inhibition of BuChE rather than AChE, and that SXF3 significantly reduced IL1β levels to normal, further confirming its anti-inflammatory activities. Hence, the selective BuChE inhibitory properties and anti-inflammatory attributes of SXF3 render it a promising candidate for further investigation in the treatment of AD.

Recent Studies on Heterocyclic Cholinesterase Inhibitors Against Alzheimer's Disease

Alzheimer's disease is a progressive and neurodegenerative disease characterized by impairment in emotion, language, memory, and cognitive judgment. There are many factors related to Alzheimer's disease, such as amyloid beta plaques (Aβ) due to impaired metabolism of amyloid precursor protein (APP), tau hyperphosphorylation, and accumulation of neurofibrillary tangles, and disruption of the cholinergic system. Disruption of the cholinergic system responsible for cognitive function and memory processes is one of the important causes of Alzheimer's disease. Therefore, cholinesterase (acetylcholinesterase and butyrylcholinesterase) inhibitors that maintain choline (acetylcholine and butyrylcholine) levels in the synaptic gap play an important role in the symptomatic treatment of Alzheimer's disease. Numerous studies have been carried out against Alzheimer's disease involving acetylcholinesterase and butyrylcholinesterase inhibitors. However, there are very few drugs (tacrine, rivastigmine, galantamine, and donepezil) approved as cholinesterase inhibitors. Therefore, cholinesterase inhibitors are needed against Alzheimer's disease. This review is focused on using heterocyclic rings that show remarkable cholinesterase inhibitory activity for Alzheimer's disease. In this review, chemical structures and structure-activity relationships of recently reported cholinesterase inhibitors are emphasized. This review will give important ideas to medicinal chemists in the discovery and development of potent cholinesterase inhibitors in their future studies.

Contilisant-Belinostat Hybrids: Polyfunctionalized Indole Derivatives as Multineurotarget Drugs for the Potential Treatment of Alzheimer's Disease

In this work, we designed, synthesized, and evaluated two types of multineurotargeting compounds using a pharmacophore merging strategy, aiming to develop potential treatments for Alzheimer's disease. We combined belinostat, an FDA-approved unselective histone deacetylase (HDAC) inhibitor, with the 5-substituted indole core of contilisant, known for its antioxidant and neuroprotective properties as well as its potent inhibitory activity against monoamine oxidases (MAOs), acetylcholinesterase (AChE), and butyrylcholinesterase (BChE). Among these, compounds 8c (HDAC1, IC50 = 0.019 μM; HDAC6, IC50 = 0.040 μM; AChE, IC50 = 20.06 μM; BChE, IC50 = 17.10 μM; MAO-B, IC50 = 2.14 μM), and 9c (HDAC1, IC50 = 0.126 μM; HDAC6, IC50 = 0.020 μM; AChE, IC50 = 2.73 μM; BChE, IC50 = 4.03 μM; MAO-B, IC50 = 1.18 μM) emerged as the most promising candidates. These compounds warrant further investigation as potential treatments for Alzheimer's disease due to their unique inhibition profiles and favorable mode of inhibition.

Discovery of novel hybrid tryptamine-rivastigmine molecules as potent AChE and BChE inhibitors exhibiting multifunctional properties for the management of Alzheimer's disease

Contemporary research evidence has corroborated a gradual loss of central cholinergic neurons in Alzheimer's Disease (AD). This progressive deterioration leads to cognitive dysfunction and impaired motor activity, culminating in the brain cell's death in the disease. The approved drugs for AD treatment can only offer relief from symptoms without addressing the underlying pathological hallmarks of the disease. To address the limitations associated with rivastigmine (RIV), a marketed drug for AD, a series of tryptamine derivatives was designed, synthesized, and evaluated in various in-vitro and in-vivo AD models. Enzyme inhibition studies identified compounds 6d and 6e as the lead molecules with potent inhibitors against AChE (6d, IC50: 0.99 ± 0.009 nM and 6e IC50: 7.97 ± 0.016 nM and BChE (6d, IC50: 27.79 ± 0.21 nM and 6e, IC50: 0.79 ± 0.005 nM), compared to the marketed drug Riv (AChE, IC50: 6630 ± 0.76 nM, BChE IC50 = 91 ± 0.40 nM). The molecular docking and dynamics studies corroborated the enzyme inhibition studies. The PAMPA assay strongly suggested the BBB crossing ability of the lead molecules. Further, 6d and 6e demonstrated the capability to counteract oxidative stress and Aβ1-42 in various in-vitro studies. Compound 6e exhibited remarkable radical scavenging activity in the DPPH assay (IC50: 22.91 ± 1.73 μM) compared to rivastigmine (% radical scavenging activity: 3.71 ± 0.09 at 200 μM). Interestingly, 6d and 6e exhibited promising activity in the AD Drosophila model by protecting eye phenotypes from degeneration induced by Aβ1-42 toxicity and reduced mitochondrial and cellular oxidative stress in this model. Furthermore, upon oral administration, 6d and 6e could reverse scopolamine-induced amnesia by improving spatial and cognitive memory in mice at 0.3 and 0.5 mg/kg compared to rivastigmine at 3 mg/kg and were found to have potent ex-vivo anti-ChEs properties, which are correlated with the observed pro-cognitive effects in the Morris Water Maze, likely mediated through the inhibition of both cholinesterases. The expression of various neuroprotection markers, such as BDNF and TRKB, was significantly overexpressed compared to the disease control group.

Potential Azo-8-hydroxyquinoline derivatives as multi-target lead candidates for Alzheimer's disease: An in-depth in silico study of monoamine oxidase and cholinesterase inhibitors

Cognitive dysfunction in Alzheimer's disease results from a complex interplay of various pathological processes, including the dysregulation of key enzymes such as acetylcholinesterase (AChE), butyrylcholinesterase (BuChE), and monoamine oxidase B (MAO-B). This study proposes and designs a series of novel molecules derived from 8-hydroxyquinoline (Azo-8HQ) as potential multi-target lead candidates for treating AD. An exhaustive in silico analysis was conducted, encompassing docking studies, ADMET analysis, density functional theory (DFT) studies, molecular dynamics simulations, and subsequent MM-GBSA calculations to examine the pharmacological potential of these molecules with the specific targets of interest. Out of the 63 Azo-8HQ derivatives analysed, two molecules, 14c and 17c, demonstrated strong affinities for AChE, BuChE, and MAO-B, along with favourable pharmacokinetic profiles and electronic properties. Molecular dynamics simulations confirmed the stability of these molecules within the active sites of the targets, and MM-GBSA calculations revealed low binding energies, indicating robust interactions. These findings identify molecules 14c and 17c as promising multi-target candidates for the treatment of AD, based on an in-depth computational study aimed at minimizing drug development costs and time. Future work will include the synthesis of these molecules followed by in-depth in vitro and in vivo testing to validate their potential therapeutic efficacy.

Development of coumarin-inspired bifunctional hybrids as a new class of anti-Alzheimer's agents with potent in vivo efficacy

Considering the multifactorial and complex nature of Alzheimer's disease and the requirement of an optimum multifunctional anti-Alzheimer's agent, a series of triazole tethered coumarin-eugenol hybrid molecules was designed as potential multifunctional anti-Alzheimer's agents using donepezil and a template. The designed hybrid molecules were synthesized via a click chemistry approach and preliminarily screened for cholinesterase and Aβ1-42 aggregation inhibition. Among them, AS15 emerged as a selective inhibitor of AChE (IC50 = 0.047 μM) over butyrylcholinesterase (BuChE: IC50 ≥ 10 μM) with desired Aβ1-42 aggregation inhibition (72.21% at 50 μM) properties. In addition, AS15 showed protective effects against DNA damage caused by hydroxyl radicals originating from H2O2. Molecular docking and simulation studies confirmed the favorable interactions of AChE and the Aβ1-42 monomer desired for their inhibition. AS15 exhibited an LD50 value of 300 mg kg-1 and showed significant improvements in memory and learning behavior in scopolamine-induced cognition impairment mouse-based animal models (Y-maze test and Morris water maze test) for behavioral analysis. Overall outcomes suggest AS15 as a potential preclinical multifunctional candidate for the management of Alzheimer's disease, and it serves as a promising lead for further development of potent and safer multifunctional anti-Alzheimer's agents.

Synthesis, docking, pharmacokinetic prediction, and acetylcholinesterase inhibitory evaluation of N-(2-(piperidine-1-yl)ethyl)benzamide derivatives as potential anti-Alzheimer agents

Background and purpose

Alzheimer's disease is the most common form of dementia and the sixth most common cause of death in the US according to the Alzheimer's Association. As regards, to date, no effective treatments are available because of the multifactorial nature of the disease, therefore, a large body of recent research has been allocated to the design and development of multi-target-directed ligands that can become effective drug candidates.

Experimental approach

A novel series of benzamide derivatives (5a-5l) containing piperidine core were synthesized in the current work. After identification of the chemical structures of the members of this series using 1H NMR, IR, and MS spectra, their anti-acetylcholinesterase activity was assessed by the Ellman᾽s test. Docking studies were also performed to investigate the binding mode and determine the interacting amino acids with the corresponding ligands. Finally, the pharmacokinetic (ADME parameters) of the most potent derivative (5d) was predicted and compared with donepezil.

Findings/Results

Compound 5d possessing the fluorine atom substitution at position ortho was the most active compound in these series (IC50 = 13 ± 2.1 nM). This compound demonstrated superior activity than the reference drug donepezil (IC50 = 0.6 ± 0.05 µM). Molecular docking showed a significant hydrogen bonding of the carbonyl group of compounds 5d with tyrosine 121 into the active site of acetylcholinesterase. Fortunately, this compound showed better promising ADME properties than donepezil.

Conclusion and implication

The benzamide derivatives introduced in this paper could be proposed as potential anti-acetylcholinesterase.

Assessing the Potential of 1,2,3-Triazole-Dihydropyrimidinone Hybrids Against Cholinesterases: In Silico, In Vitro, and In Vivo Studies

Combining the pharmacological properties of the 1,2,3-triazole and dihydropyrimidinone classes of compounds, two small families of mono- and di(1,2,3-triazole)-dihydropyrimidinone hybrids, A and B, were previously synthesized. The main objective of this work was to investigate the potential anti-Alzheimer effects of these hybrids. The inhibitory activities of cholinesterases (AChE and BuChE), antioxidant activity, and the inhibitory mechanism through in silico (molecular docking) and in solution (STD-NMR) experiments were evaluated. The 1,2,3-triazole-dihydropyrimidinone hybrids (A and B) showed moderate in vitro inhibitory activity on eqBuChE (IC50 values between 1 and 58.4 μM). The best inhibitor was the hybrid B4, featuring two 1,2,3-triazole cores, which exhibited stronger inhibition than galantamine, with an IC50 of 1 ± 0.1 μM for eqBuChE, through a mixed inhibition mechanism. Among the hybrids A, the most promising inhibitor was A1, exhibiting an IC50 of 12 ± 2 µM, similar to that of galantamine. Molecular docking and STD-NMR experiments revealed the key binding interactions of these promising inhibitors with BuChE. Hybrids A and B did not display Artemia salina toxicity below 100 μM.

Design of Promising Thiazoloindazole-Based Acetylcholinesterase Inhibitors Guided by Molecular Docking and Experimental Insights

Alzheimer's disease is characterized by a progressive deterioration of cognitive function and memory loss, and it is closely associated with the dysregulation of cholinergic neurotransmission. Since acetylcholinesterase (AChE) is a critical enzyme in the nervous system, responsible for breaking down the neurotransmitter acetylcholine, its inhibition holds a significant interest in the treatment of various neurological disorders. Therefore, it is crucial to develop efficient AChE inhibitors capable of increasing acetylcholine levels, ultimately leading to improved cholinergic neurotransmission. The results reported here represent a step forward in the development of novel thiazoloindazole-based compounds that have the potential to serve as effective AChE inhibitors. Molecular docking studies revealed that certain of the evaluated nitroindazole-based compounds outperformed donepezil, a well-known AChE inhibitor used in Alzheimer's disease treatment. Sustained by these findings, two series of compounds were synthesized. One series included a triazole moiety (Tl45a-c), while the other incorporated a carbazole moiety (Tl58a-c). These compounds were isolated in yields ranging from 66 to 87% through nucleophilic substitution and Cu(I)-catalyzed azide-alkyne 1,3-dipolar cycloaddition (CuAAC) reactions. Among the synthesized compounds, the thiazoloindazole-based 6b core derivatives emerged as selective AChE inhibitors, exhibiting remarkable IC50 values of less than 1.0 μM. Notably, derivative Tl45b displays superior performance as an AChE inhibitor, boasting the lowest IC50 (0.071 ± 0.014 μM). Structure-activity relationship (SAR) analysis indicated that derivatives containing the bis(trifluoromethyl)phenyl-triazolyl group demonstrated the most promising activity against AChE, when compared to more rigid substituents such as carbazolyl moiety. The combination of molecular docking and experimental synthesis provides a suitable and promising strategy for the development of new efficient thiazoloindazole-based AChE inhibitors.

Design and synthesis of ligustrazine derivatives as potential anti-Alzheimer's agents

A novel series of ligustrazine derivatives was designed, synthesized, and evaluated as acetylcholinesterase (AChE) and butylcholinesterase (BuChE) inhibitors for the treatment of Alzheimer's disease (AD). In vitro studies displayed that some of the synthesized compounds revealed promising AChE and BuChE inhibitory effects. Particularly, compounds E12 and E27, indicated highly AChE inhibitory activity with IC50 values of 1.85 μM and 0.98 μM, respectively and showed noteworthy protective effects against on glutamate-induced SH-SY5Y cells damage at 1 μM and 10 μM concentrations. Furthermore, molecular simulation docking elucidates compounds E12 and E27 interacting with residues in the binding site of AChE (PDB code: 4EY7) and BuChE (PDB code: 1P0I), emphasizing the protein residues that participate in the main interactions with the two targets. Taken together, these results revealed that compounds E12 and E27 might be potential lead compounds for further structure optimization in the drug-discovery process against AD.

Design, Synthesis, Nematicidal Evaluation, and Molecular Docking Study of Pyrano[3,2-c]pyridones against Meloidogyne incognita

Root-knot nematodes pose a serious threat to crops by affecting production and quality. Over a period of time, substantial work has been done toward the development of effective and environmentally benign nematicidal compounds. However, due to the inefficiencies of previously reported synthetics in achieving the target of safe, selective, and effective treatment, it is necessary to develop new efficacious and safer nematicidal agents considering human health and environment on top priority. This work aims to highlight the efficient and convenient l-proline catalyzed synthesis of pyrano[3,2-c]pyridone and their use as potential nematicidal agents. In vitro results of larval mortality and egg hatching inhibition revealed maximum nematicidal activity against Meloidogyne incognita from compounds 15b, 15m, and 15w with LC50 values of 28.8, 46.8, and 49.18 μg/mL at 48 h, respectively. Under similar conditions, pyrano[3,2-c]pyridones derivatives 15b (LC50 = 28.8 μg/mL) was found at par with LC50 (26.92 μg/mL) of commercial nematicide carbofuran. The in vitro results were further validated with in silico studies with the most active compound 15b nematicidal within the binding to the pocket of acetylcholine esterase (AChE). In docking, binding free energy values for compound 15b were found to be -6.90 kcal/mol. Results indicated that pyrano[3,2-c]pyridone derivatives have the potential to control M. incognita.

Ceanothanes Derivatives as Peripheric Anionic Site and Catalytic Active Site Inhibitors of Acetylcholinesterase: Insights for Future Drug Design

Alzheimer's disease (AD) is a multifactorial and fatal neurodegenerative disorder. Acetylcholinesterase (AChE) plays a key role in the regulation of the cholinergic system and particularly in the formation of amyloid plaques; therefore, the inhibition of AChE has become one of the most promising strategies for the treatment of AD, particularly concerning AChE inhibitors that interact with the peripheral anionic site (PAS). Ceanothic acid isolated from the Chilean Rhamnaceae plants is an inhibitor of AChE through its interaction with PAS. In this study, six ceanothic acid derivatives were prepared, and all showed inhibitory activity against AChE. The structural modifications were performed starting from ceanothic acid by application of simple synthetic routes: esterification, reduction, and oxidation. AChE activity was determined by the Ellmann method for all compounds. Kinetic studies indicated that its inhibition was competitive and reversible. According to the molecular coupling and displacement studies of the propidium iodide test, the inhibitory effect of compounds would be produced by interaction with the PAS of AChE. In silico predictions of physicochemical properties, pharmacokinetics, drug-likeness, and medicinal chemistry friendliness of the ceanothane derivatives were performed using the Swiss ADME tool.

Preferential Door for Ligand Binding and Unbinding Pathways in Inhibited Human Acetylcholinesterase

Rising global population and increased food demands have resulted in the increased use of organophosphate pesticides (OPs), leading to toxin accumulation and transmission to humans. Pralidoxime (2-PAM), an FDA-approved drug, serves as an antidote for OP therapy. However, the atomic-level detoxification mechanisms regarding the design of novel antidotes remain unclear. This is the first study to examine the binding and unbinding pathways of 2-PAM to human acetylcholinesterase (HuAChE) through three identified doors using an enhanced sampling method called ligand-binding parallel cascade selection molecular dynamics (LB-PaCS-MD). Remarkably, LB-PaCS-MD could identify a predominant in-line binding mechanism through the acyl door at 63.79% ± 6.83%, also implicating it in a potential unbinding route (90.14% ± 4.22%). Interestingly, crucial conformational shifts in key residues, W86, Y341, and Y449, and the Ω loop significantly affect door dynamics and ligand binding modes. The LB-PaCS-MD technique can study ligand-binding pathways, thereby contributing to the design of antidotes and covalent drugs.

Determination of Acetylcholinesterase Activity Based on Ratiometric Fluorescence Signal Sensing

Acetylcholinesterase (AChE) plays an important role in the treatment of human diseases, environmental security and global food supply. In this study, the simple fluorescent indicators and MnO2 nanosheets were developed and integrated to establish a ratiometric fluorescence sensing system for the detection of AChE activity. Two fluorescence signals could be recorded independently at the same excitation wavelength, which extended the detection range and enhanced the visibility of results. Fluorescence of F-PDA was quenched by MnO2 nanosheets on account of inner filtering effect. Meanwhile, the nonfluorescent OPD was catalytically oxidized to 2,3-diaminophenazine by MnO2 nanosheets. The acetylcholine (ATCh) was catalytically hydrolyzed by AChE to enzymatic thiocholine, which decomposed MnO2 to Mn2+, recovered the fluorescence of F-PDA and reduced the emission of ox-OPD. Utilizing the fluorescence intensity ratio F468/F558 as the signal readout, the ratiometric fluorescence method was established to detect AChE activity. Under the excitation wavelength of 410 nm, the ratio F460/F558 against the AChE concentration demonstrated two linear relationships in the range 0.05 -1.0 and 1.0-50 U·L- 1 with a limit of detection (LOD) of 0.073 U·L- 1. The method was applied to the detection of AChE activity and the analysis of the inhibitor Huperzine-A. Due to the advantages of high sensitivity and favorable selectivity, the method possesses an application prospect in the activity deteceion of AChE and the screening of inhibitors.

Amino-7,8-dihydro-4H-chromenone derivatives as potential inhibitors of acetylcholinesterase and butyrylcholinesterase for Alzheimer's disease management; in vitro and in silico study

In this article, we present the design and synthesis of amino-7,8-dihydro-4H-chromenone derivatives as possible inhibitors of acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) for the management of Alzheimer's disease (AD). The target compounds were evaluated against AChE and BChE in vitro, and 4k exhibited good potency against BChE (IC50 = 0.65 ± 0.13 µM) compared with donepezil used as a positive control. Kinetic studies revealed that compound 4k exhibited a competitive-type inhibition with a Ki value of 0.55 µM. Molecular docking and molecular dynamics simulations further supported the rationality of our design strategy, as 4k showed promising binding interactions with the active sites of BChE. Overall, our findings highlight the potential of amino-7,8-dihydro-4H-chromenone derivatives as promising candidates for developing novel therapeutics targeting cholinesterase in managing AD.

Chemical library design, QSAR modeling and molecular dynamics simulations of naturally occurring coumarins as dual inhibitors of MAO-B and AChE

Coumarins are a highly privileged scaffold in medicinal chemistry. It is present in many natural products and is reported to display various pharmacological properties. A large plethora of compounds based on the coumarin ring system have been synthesized and were found to possess biological activities such as anticonvulsant, antiviral, anti-inflammatory, antibacterial, antioxidant as well as neuroprotective properties. Despite the wide activity spectrum of coumarins, its naturally occurring derivatives are yet to be investigated in detail. In the current study, a chemical library was created to assemble all chemical information related to naturally occurring coumarins from the literature. Additionally, a multi-stage virtual screening combining QSAR modeling, molecular docking, and ADMET prediction was conducted against monoamine oxidase B and acetylcholinesterase, two relevant targets known for their neuroprotective properties and 'disease-modifying' potential in Parkinson's and Alzheimer's disease. Our findings revealed ten coumarin derivatives that may act as dual-target drugs against MAO-B and AChE. Two coumarin candidates were selected from the molecular docking study: CDB0738 and CDB0046 displayed favorable interactions for both proteins as well as suitable ADMET profiles. The stability of the selected coumarins was assessed through 100 ns molecular dynamics simulations which revealed promising stability through key molecular interactions for CDB0738 to act as dual inhibitor of MAO-B and AChE. However, experimental studies are necessary to evaluate the bioactivity of the proposed candidate. The current results may generate an increasing interest in bioprospecting naturally occurring coumarins as potential candidates against relevant macromolecular targets by encouraging virtual screening studies against our chemical library.Communicated by Ramaswamy H. Sarma.

Design, synthesis, and biological evaluation of novel tryptanthrin derivatives as selective acetylcholinesterase inhibitors for the treatment of Alzheimer's disease

Two novel series of tryptanthrin (TRYP) derivatives were designed and synthesized as multifunctional agents for the treatment of Alzheimer's disease (AD). Inhibition assay against cholinesterase (ChE) indicated that these derivatives can act as acetylcholinesterase (AChE) inhibitors with selectivity over butyrylcholinesterase (BuChE). Among them, n1 exhibited the most excellent ChE inhibitory potency (AChE, IC50 = 12.17 ± 1.50 nM; BuChE, IC50 = 6.29 ± 0.48 μΜ; selectivity index = 517). Molecular docking studies indicated that compound n1 can interact with amino acid residues in the catalytic active site and peripheral anionic site of AChE and the molecular dynamics (MD) simulation studies demonstrated that the AChE-n1 complex had good stability. N1 also exhibited anti-amyloid-β (Aβ) aggregation (63.48 % ± 1.02 %, 100 μΜ) and anti-neuroinflammation activity (NO, IL-1β, TNF-α; IC50 = 2.13 ± 0.54 μΜ, 2.21 ± 0.37 μΜ, 2.47 ± 0.07 μΜ, respectively), and n1 had neuroprotective and metal-chelating properties. Further studies indicated n1 had proper blood-brain barrier permeability in the Parallel artificial membrane permeation assay. In vivo studies found that n1 effectively improved learning and memory impairment in scopolamine-induced AD mouse models. Nissl staining ofmice hippocampaltissue sections revealed that n1 restored neuronal cells in the hippocampus CA3 and CA1 regions. These findings suggested that n1 can be a promising compound for further development of multifunctional agents for AD treatment.

Synthesis and molecular docking simulation of new benzimidazole-thiazole hybrids as cholinesterase inhibitors

Dementia is a cognitive disturbance that is generally correlated with central nervous system diseases, especially Alzheimer's disease. The limited number of medications available is insufficient to improve the lifestyle of the patients suffering from this disease. Thus, new benzimidazole-thiazole hybrids (3-10) were designed and synthesized as acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) inhibitory agents. The in vitro evaluation displayed that the derivatives 4b, 4d, 5b, 6a, 7a, and 8b demonstrated dual inhibitory efficiency against both AChE with IC50 ranging from 4.55 to 8.62 µM and BChE with IC50 ranging from 3.50 to 8.32 µM. By analyzing the Lineweaver-Burk plot, an uncompetitive form of inhibition was determined for the highly active compound 4d, revealing its inhibition type. The human telomerase reverse transcriptase-immortalized retinal pigment epithelial cell line was used to ensure the safety of the most potent cholinesterase inhibitors. Furthermore, compounds 4b, 4d, 5b, 6a, 7a, and 8b were evaluated for their neuroprotective and antioxidant properties, as well as their ability to suppress COX-2. The results demonstrated that compounds 4d, 5b, and 8b presented significant neuroprotection efficiency against H2 O2 -induced damage in SH-SY5Y cells with % cell viability of 67.42 ± 7.90%, 62.51 ± 6.71%, and 72.61 ± 8.10%, respectively, while the tested candidates did not reveal significant antioxidant activity. Otherwise, compounds 4b, 6a, 7a, and 8b displayed outstanding COX-2 inhibition effects with IC50 ranging from 0.050 to 0.080 μM relative to celecoxib (IC50  = 0.050 µM). In addition, molecular docking was carried out for the potent benzimidazole-thiazole hybrids with the active sites of both AChE (PDB ID: 4EY7) and BChE (PDB code: 1P0P). The tested candidates fit well in the active sites of both portions, with docking scores ranging from -8.65 to -6.64 kcal/mol (for AChE) and -8.71 to -7.73 kcal/mol (for BChE). In silico results show that the synthesized benzimidazole-thiazole hybrids have good physicochemical and pharmacokinetic properties with no Lipinski rule violations. The preceding results exhibited that compound 4d could be used as a new template for developing more significant cholinesterase inhibitors in the future.

Pyrimidine-morpholine hybrids as potent druggable therapeutics for Alzheimer's disease: Synthesis, biochemical and in silico analyses

The identification of effective and druggable cholinesterase inhibitors to treat progressive neurodegenerative Alzheimer's disorder remains a continuous drug discovery hunt. In this perspective, the present study investigates the design and discovery of pyrimidine-morpholine hybrids (5a-l) as potent cholinesterase inhibitors. Palladium-catalyzed Suzuki-Miyaura cross-coupling reaction was employed to introduce the structural diversity on the pyrimidine heterocyclic core. A range of commercially available boronic acids was successfully coupled showing a high functional group tolerance. In vitro cholinesterase inhibitory potential using Ellman's method revealed significantly strong potency. Compound 5h bearing a meta-tolyl substituent at 2-position of pyrimidine ring emerged as a lead candidate against AChE with an inhibitory potency of 0.43 ± 0.42 µM, ∼38-fold stronger value than neostigmine (IC50 = 16.3 ± 1.12 µM). Compound 5h also showed the lead inhibition against BuChE with an IC50 value of 2.5 ± 0.04 µM. The kinetics analysis of 5h revealed the non-competitive mode of inhibition against AChE whereas computational modelling results of potent leads depicted diverse contacts with the binding site amino acid residues. Molecular dynamics simulations revealed the stability of biomolecular system, while, ADME analysis demonstrated druglikeness behaviour of potent compounds. Overall, the investigated pyrimidine-morpholine scaffold presented a remarkable potential to be developed as efficacious anti-Alzheimer's drugs.

Design of electron-donating group substituted 2-PAM analogs as antidotes for organophosphate insecticide poisoning

The use of organophosphate (OPs) pesticides is widespread in agriculture and horticulture, but these chemicals can be lethal to humans, causing fatalities and deaths each year. The inhibition of acetylcholinesterase (AChE) by OPs leads to the overstimulation of cholinergic receptors, ultimately resulting in respiratory arrest, seizures, and death. Although 2-pralidoxime (2-PAM) is the FDA-approved drug for treating OP poisoning, there is difficulty in blood-brain barrier permeation. To address this issue, we designed and evaluated a series of 2-PAM analogs by substituting electron-donating groups on the para and/or ortho positions of the pyridinium core using in silico techniques. Our PCM-ONIOM2 (MP2/6-31G*:PM7//B3LYP/6-31G*:UFF) binding energy results demonstrated that 13 compounds exhibited higher binding energy than 2-PAM. The analog with phenyl and methyl groups substituted on the para and ortho positions, respectively, showed the most favorable binding characteristics, with aromatic residues in the active site (Y124, W286, F297, W338, and Y341) and the catalytic residue S203 covalently bonding with paraoxon. The results of DS-MD simulation revealed a highly favorable apical conformation of the potent analog, which has the potential to enhance reactivation of AChE. Importantly, newly designed compound demonstrated appropriate drug-likeness properties and blood-brain barrier penetration. These results provide a rational guide for developing new antidotes to treat organophosphate insecticide toxicity.

Investigation on Novel E/Z 2-Benzylideneindan-1-One-Based Photoswitches with AChE and MAO-B Dual Inhibitory Activity

The multitarget therapeutic strategy, as opposed to the more traditional 'one disease-one target-one drug', may hold promise in treating multifactorial neurodegenerative syndromes, such as Alzheimer's disease (AD) and related dementias. Recently, combining a photopharmacology approach with the multitarget-directed ligand (MTDL) design strategy, we disclosed a novel donepezil-like compound, namely 2-(4-((diethylamino)methyl)benzylidene)-5-methoxy-2,3-dihydro-1H-inden-1-one (1a), which in the E isomeric form (and about tenfold less in the UV-B photo-induced isomer Z) showed the best activity as dual inhibitor of the AD-related targets acetylcholinesterase (AChE) and monoamine oxidase B (MAO-B). Herein, we investigated further photoisomerizable 2-benzylideneindan-1-one analogs 1b-h with the unconjugated tertiary amino moiety bearing alkyls of different bulkiness and lipophilicity. For each compound, the thermal stable E geometric isomer, along with the E/Z mixture as produced by UV-B light irradiation in the photostationary state (PSS, 75% Z), was investigated for the inhibition of human ChEs and MAOs. The pure E-isomer of the N-benzyl(ethyl)amino analog 1h achieved low nanomolar AChE and high nanomolar MAO-B inhibition potencies (IC50s 39 and 355 nM, respectively), whereas photoisomerization to the Z isomer (75% Z in the PSS mixture) resulted in a decrease (about 30%) of AChE inhibitory potency, and not in the MAO-B one. Molecular docking studies were performed to rationalize the different E/Z selectivity of 1h toward the two target enzymes.

Exploring the potential of a novel phenoxyethyl piperidine derivative with cholinesterase inhibitory properties as a treatment for dementia: Insights from STZ animal model of dementia

Alzheimer's disease (AD) is a neurodegenerative disease, often characterized by progressive deficits in memory and cognitive functions. Cholinesterase inhibitors have been introduced as promising agents to enhance cognition and memory in both human patients and animal models of AD. In the current study, we assessed the effects of a synthetic phenoxyethyl piperidine derivative, compound 7c, as a novel dual inhibitor of acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE), on learning and memory, as well as serum and hippocampal AChE levels in an animal model of AD. The model of dementia was induced by intracerebroventricular injection of streptozotocin (STZ, 2 mg/kg) to male Wistar rats. STZ-treated rats received compound 7c (3, 30, and 300 µg/kg) for five consecutive days. ​Passive avoidance (PA) learning and memory, as well as spatial learning and memory using Morris water maze, were evaluated. The level of AChE was measured in the serum and the left and right hippocampus. Findings demonstrated that compound 7c (300 µg/kg) was able to reverse STZ-induced impairments in PA memory, while also reduced the increased AChE level in the left hippocampus. Taken together, compound 7c appeared to act as a central AChE inhibitor, and its role in alleviating cognitive deficits in the AD animal model suggests that it may have therapeutic potential in AD dementia. Further research is required to assess the effectiveness of compound 7c in more reliable models of AD in light of these preliminary findings.

Inhibition of Human Cholinesterases and in vitro β-Amyloid Aggregation by Rationally Designed Peptides

The multifactorial nature of Alzheimer's disease (AD) is now widely recognized, which has increased the interest in compounds that can address more than one AD-associated targets. Herein, we report the inhibitory activity on the human cholinesterases (acetylcholinesterase, hAChE and butyrylcholinesterase, hBChE) and on the AChE-induced β-amyloid peptide (Aβ) aggregation by a series of peptide derivatives designed by mutating aliphatic residues for aromatic ones. We identified peptide W3 (LGWVSKGKLL-NH2 ) as an interesting scaffold for the development of new anti-AD multitarget-directed drugs. It showed the lowest IC50 value against hAChE reported for a peptide (0.99±0.02 μM) and inhibited 94.2 %±1.2 of AChE-induced Aβ aggregation at 10 μM. Furthermore, it inhibited hBChE (IC50 , 15.44±0.91 μM), showed no in vivo toxicity in brine shrimp and had shown moderated radical scavenging and Fe2+ chelating capabilities in previous studies. The results are in line with multiple reports showing the utility of the indole moiety for the development of cholinesterase inhibitors.

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

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

Validation of Acetylcholinesterase Inhibition Machine Learning Models for Multiple Species

Acetylcholinesterase (AChE) is an important enzyme and target for human therapeutics, environmental safety, and global food supply. Inhibitors of this enzyme are also used for pest elimination and can be misused for suicide or chemical warfare. Adverse effects of AChE pesticides on nontarget organisms, such as fish, amphibians, and humans, have also occurred as a result of biomagnifications of these toxic compounds. We have exhaustively curated the public data for AChE inhibition data and developed machine learning classification models for seven different species. Each set of models were built using up to nine different algorithms for each species and Morgan fingerprints (ECFP6) with an activity cutoff of 1 μM. The human (4075 compounds) and eel (5459 compounds) consensus models predicted AChE inhibition activity using external test sets from literature data with 81% and 82% accuracy, respectively, while the reciprocal cross (76% and 82% percent accuracy) was not species-specific. In addition, we also created machine learning regression models for human and eel AChE inhibition to return a predicted IC₅₀ value for a queried molecule. We did observe an improved species specificity in the regression models, where a human support vector regression model of human AChE inhibition (3652 compounds) predicted the IC₅₀s of the human test set to a better extent than the eel regression model (4930 compounds) on the same test set, based on mean absolute percentage error (MAPE = 9.73% vs 13.4%). The predictive power of these models certainly benefits from increasing the chemical diversity of the training set, as evidenced by expanding our human classification model by incorporating data from the Tox21 library of compounds. Of the 10 compounds we tested that were predicted active by this expanded model, two showed >80% inhibition at 100 μM. This machine learning approach therefore offers the ability to rapidly score massive libraries of molecules against the models for AChE inhibition that can then be selected for future in vitro testing to identify potential toxins. It also enabled us to create a public website, MegaAChE, for single-molecule predictions of AChE inhibition using these models at megaache.collaborationspharma.com.

Design, synthesis and biological evaluation of novel antipyrine based α-aminophosphonates as anti-Alzheimer and anti-inflammatory agent

Herein, a series of novel antipyrine based α-aminophosphonates derivatives were synthesized and characterized. The synthesized derivatives were subjected for in vitro cholinesterase inhibition, enzyme kinetic studies, protein denaturation assay, proteinase inhibitory assay and cell viability assay. For cholinesterase inhibition, the results inferred that the test compounds possess better AChE activity (0.46 to 6.67 µM) than BuChE (2.395 to 12.47 µM). Compound 4j inhibited both AChE and BuChE (IC₅₀ = 0.475 ± 0.12 µM and 2.95 ± 0.16 µM, respectively), implying that it serves as a dual AChE/BuChE inhibitor. Also, kinetic studies revealed that compound 4j exhibits mixed-type inhibition against both AChE and BuChE, with K_i values of 3.003 µM and 5.750 µM, respectively. Further, protein denaturation and proteinase inhibitory assays were used to test in vitro anti-inflammatory potential. It was found that compound 4o exhibited highest activity against protein denaturation (IC₅₀ = 42.64 ± 0.19 µM) and proteinase inhibition (IC₅₀ = 37.57 ± 0.19 µM) when compared to diclofenac. In addition, cell viability assay revealed that active compounds possess no cytotoxicity against N2a cell and RAW 264.7 macrophages. Finally, molecular docking experiments for AChE, BuChE, and COX-2 were conducted to better understand the binding modes of active compounds.Communicated by Ramaswamy H. Sarma.

Tacrine-Based Hybrids: Past, Present, and Future

Alzheimer's disease (AD) is a neurodegenerative disorder which is characterized by β-amyloid (Aβ) aggregation, τ-hyperphosphorylation, and loss of cholinergic neurons. The other important hallmarks of AD are oxidative stress, metal dyshomeostasis, inflammation, and cell cycle dysregulation. Multiple therapeutic targets may be proposed for the development of anti-AD drugs, and the "one drug-multiple targets" strategy is of current interest. Tacrine (THA) was the first clinically approved cholinesterase (ChE) inhibitor, which was withdrawn due to high hepatotoxicity. However, its high potency in ChE inhibition, low molecular weight, and simple structure make THA a promising scaffold for developing multi-target agents. In this review, we summarized THA-based hybrids published from 2006 to 2022, thus providing an overview of strategies that have been used in drug design and approaches that have resulted in significant cognitive improvements and reduced hepatotoxicity.

Ring-fused 3β-acetoxyandrost-5-enes as novel neuroprotective agents with cholinesterase inhibitory properties

Alzheimer´s disease (AD) is an intellectual disorder caused by organic brain damage and cerebral atrophy, characterized by the loss of memory, judgment, and abstract thinking followed by declining cognitive functions, language, and the ability to perform daily living activities. Many efforts have been made to decrease the effects of the disease but also to block the neurodegenerative process. Cholinesterase inhibitors (ChEIs) are a group of medicines that act at the neurotransmission of acetylcholine, preventing its excessive breakdown and helping to improve cognitive functions in patients with AD. In this work, 16 chiral steroids, namely ring-fused 3β-acetoxyandrost-5-ene derivatives, their precursor and two 16-dehydroprogesterone-derived dioximes, were assessed as cholinesterase inhibitors and neuroprotective agents. The results demonstrated that some of the tested steroids are cholinesterase inhibitors and the majority selective for acetylcholinesterase inhibition. Albeit, one ring-fused 3β-acetoxyandrost-5-ene containing N-methylpiperidine ring (compound 2g) demonstrated to be a selective and potent inhibitor of the butyrylcholinesterase enzyme. (S)- 4,4a,5,6,7,8-(hexahydronaphthalen-2-one)-fused 3β-acetoxyandrost-5-ene (compound 6) showed high neuroprotective effect, high ability to restore the mitochondrial membrane potential from glutamate intoxication, and dramatic improvement in cell morphology. The described results provided relevant structure-activity relationship data.

Pyrazoline scaffold: hit identification to lead synthesis and biological evaluation as antidiabetic agents

Background: Mining of novel scaffolds as potential DPP-IV inhibitors for future development of potential candidates as antidiabetic agents to address global issues. Methodology: The identified hit KB-10 from a previously reported study was taken as a lead for designing a library of analogues and screened initially based on in silico parameters and docking score. A series of selected (2[4-(1-acetyl-5-phenyl-4,5-dihydro-1H-pyrazol-3-yl)phenoxy]-1-phenylethanone derivatives were synthesized and evaluated through in vitro studies. Compounds KB-23, KB-22 and KB-06 were found to be as potent, with IC₅₀ values of 0.10 μM, 0.12 μM and 0.35 μM, respectively. They also showed promising antihyperglycemic potential in in vivo studies (oral glucose tolerance tests) in Wistar rats. Conclusion: This work establishes pyrazoline analogues KB-23, KB-22 and KB-06 as promising starting points for the development of potential antidiabetic agents.

Synthesis, Characterization and Biological Evaluation of Benzothiazole-Isoquinoline Derivative

Currently, no suitable clinical drugs are available for patients with neurodegenerative diseases complicated by depression. Based on a fusion technique to create effective multi-target-directed ligands (MTDLs), we synthesized a series of (R)-N-(benzo[d]thiazol-2-yl)-2-(1-phenyl-3,4-dihydroisoquinolin-2(1H)-yl) acetamides with substituted benzothiazoles and (S)-1-phenyl-1,2,3,4-tetrahydroisoquinoline. All compounds were tested for their inhibitory potency against monoamine oxidase (MAO) and cholinesterase (ChE) by in vitro enzyme activity assays, and further tested for their specific inhibitory potency against monoamine oxidase B (MAO-B) and butyrylcholinesterase (BuChE). Among them, six compounds (4b-4d, 4f, 4g and 4i) displayed excellent activity. The classical antidepressant forced swim test (FST) was used to verify the in vitro results, revealing that six compounds reduced the immobility time significantly, especially compound 4g. The cytotoxicity of the compounds was assessed by the MTT method and Acridine Orange (AO) staining, with cell viability found to be above 90% at effective compound concentrations, and not toxic to L929 cells reversibility, kinetics and molecular docking studies were also performed using compound 4g, which showed the highest MAO-B and BuChE inhibitory activities. The results of these studies showed that compound 4g binds to the primary interaction sites of both enzymes and has good blood-brain barrier (BBB) penetration. This study provides new strategies for future research on neurodegenerative diseases complicated by depression.

Novel Chromone-Containing Allylmorpholines Induce Anxiolytic-like and Sedative Effects in Adult Zebrafish

Chromone-containing allylmorpholines (CCAMs) are a novel class of compounds that have demonstrated acetyl- and butyryl-cholinesterase-inhibiting and N-methyl-D-aspartate (NMDA) receptor-blocking properties in vitro, but their in vivo pharmacological activity remains underexplored. In this work, we evaluated the psychotropic activity of five different CCAMs (1 (9a), 2 (9j), 3 (9l), 4 (33a), and 5 (33b)) using the novel tank test (NTT) and light/dark box (LDB) test in adult zebrafish. The CCAMs were screened in the NTT at a range of concentrations, and they were found to induce a dose-dependent sedative effect. Compound 4 (33a) was also evaluated using the LDB test, and it was found to have anxiolytic-like properties at low concentrations. To assess the potential contribution of the glutamate and cholinergic mechanisms in the effects of the CCAMs, we conducted experiments with pre-exposure to putative antagonists, NMDA and biperiden. Neither biperiden nor NMDA were able to diminish or cancel the effects of the CCAMs, countering the in vitro data obtained in previous studies. The apparent discrepancy could be related to the specifics of CCAM metabolism or to the interspecies differences between the putative target proteins, possibly due to the relatively low identity percentage of their sequences. Although further research in mammals is required in order to establish their pharmacological properties, novel CCAMs may represent an appealing group of psychoactive drug candidates.

Synthesis, spectroscopic, topological, hirshfeld surface analysis, and anti-covid-19 molecular docking investigation of isopropyl 1-benzoyl-4-(benzoyloxy)-2,6-diphenyl-1,2,5,6-tetrahydropyridine-3-carboxylate

Isopropyl 1-benzoyl-4-(benzoyloxy)-2,6-diphenyl-1,2,5,6-tetrahydropyridine-3-carboxylate (IDPC) was synthesized and characterized via spectroscopic (FT-IR and NMR) techniques. Hirshfeld surface and topological analyses were conducted to study structural and molecular properties. The energy gap (Eg), frontier orbital energies (EHOMO, ELUMO) and reactivity parameters (like chemical hardness and global hardness) were calculated using density functional theory with B3LYP/6-311++G (d,p) level of theory. Molecular docking of IDPC at the active sites of SARS-COVID receptors was investigated. IDPC molecule crystallized in the centrosymmetric triclinic ( P 1 ¯ ) space group. The topological and Hirshfeld surface analysis revealed that covalent, non-covalent and intermolecular H-bonding interactions, and electron delocalization exist in the molecular framework. Higher binding score (-6.966 kcal/mol) of IDPC at the active site of SARS-COVID main protease compared to other proteases suggests that IDPC has the potential of blocking polyprotein maturation. H-bonding and π-cationic and interactions of the phenyl ring and carbonyl oxygen of the ligand indicate the effective inhibiting potential of the compound against the virus.

4-(4-(((1H-Benzo[d][1,2,3]triazol-1-yl)oxy)methyl)-1H-1,2,3-triazol-1-yl)-7-chloroquinoline

The 1,2,3-triazole ring system can be easily obtained by widely used copper-catalyzed click reaction of azides with alkynes. 1,2,3-triazole exhibits myriad of biological activities, including antibacterial antimalarial, and antiviral activities. We herein reported the synthesis of quinoline-based [1,2,3]-triazole hybrid derivative via Cu(I)-catalyzed click reaction of 4-azido-7-chloroquinoline with alkyne derivative of hydroxybenzotriazole (HOBt). The compound was fully characterized by proton nuclear magnetic resonance (1H-NMR), carbon-13 nuclear magnetic resonance (13C-NMR), correlated spectroscopy (1H-1H-COSY), heteronuclear single quantum coherence (HSQC) and distortionless enhancement by polarization transfer (DEPT-135 and DEPT-90) NMR, ultraviolet (UV) and Fourier-transform infrared (FTIR) spectroscopies, and high-resolution mass spectrometry (HRMS). Computational studies were enrolled to predict the interaction of the synthesized compound with acetylcholinesterase, a target of primary relevance for developing new therapeutic options to counteract neurodegeneration. Moreover, the drug-likeness of the compound was also investigated by predicting its pharmacokinetic properties.

Microwave-enhanced synthesis of 26-amino-22-oxocholestanes and their cytotoxic activity

The synthesis of a series of 26-amino-22-oxocholestanes derived from diosgenin was accomplished via the substitution of an iodine atom at C-26 by primary and secondary amines. The reactions were conducted in refluxing acetonitrile and through microwave-assisted heating. The latter shows significant improvements in terms of reaction times going from hours to a few minutes or even seconds for completion. Only one of the selected amines, 4-aminourazole, did not yield the substitution product and the imine formation pathway was investigated instead, achieving the 26-iminourazole-22-oxocholestane. All the final products have been characterized and the cytotoxic activity of three of them has been evaluated in SiHa, MCF-7 and MDA tumor cell lines by the sulforhodamine B assay.

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.

MnO2/DNAzyme-mediated ratiometric fluorescence assay of acetylcholinesterase

A ratiometric fluorescent probe (MnO2/DNAzyme) is constructed. In the presence of AChE, the product thiocholine reduces MnO2 to Mn2+. The released H1 strands hybridizes with H2 strands to activate DNAzyme and cause cleavage of DNA-F signal probe.

Validation of the portable virtual reality training system for robotic surgery (PoLaRS): a randomized controlled trial

BACKGROUND

As global use of surgical robotic systems is steadily increasing, surgical simulation can be an excellent way for robotic surgeons to acquire and retain their skills in a safe environment. To address the need for training in less wealthy parts of the world, an affordable surgical robot simulator (PoLaRS) was designed.

METHODS

The aim of this pilot study is to compare learning curve data of the PoLaRS prototype with those of Intuitive Surgical's da Vinci Skills Simulator (dVSS) and to establish face- and construct validity. Medical students were divided into two groups; the test group (n = 18) performing tasks on PoLaRS and dVSS, and the control group (n = 20) only performing tasks on the dVSS. The performance parameters were Time, Path length, and the number of collisions. Afterwards, the test group participants filled in a questionnaire regarding both systems.

RESULTS

A total of 528 trials executed by 38 participants were measured and included for analyses. The test group significantly improved in Time, Path Length and Collisions during the PoLaRS test phase (P ≤ 0.028). No differences was found between the test group and the control group in the dVSS performances during the post-test phase. Learning curves showed similar shapes between both systems, and between both groups. Participants recognized the potential benefits of simulation training on the PoLaRS system.

CONCLUSIONS

Robotic surgical skills improved during training with PoLaRS. This shows the potential of PoLaRS to become an affordable alternative to current surgical robot simulators. Validation with similar tasks and different expert levels is needed before implementing the training system into robotic training curricula.

Research progress in pharmacological activities and structure-activity relationships of tetralone scaffolds as pharmacophore and fluorescent skeleton

The tetralone and tetralone derivatives, as crucial structural scaffolds of potential novel drugs targeted at multiple biological end-points, are normally found in several natural compounds and also, it can be used as parental scaffold and/or intermediate for the synthesis of a series of pharmacologically active compounds with a broad-spectrum of bioactivities including antibacterial, antitumor, CNS effect and so on. Meanwhile, SAR information of its analogues has drawn attentions among medicinal chemists, which could contribute to the further research related to tetralone derivatives aimed at multiple targets. This review encompasses pharmacological activities, SAR analysis and docking study of tetralone and its derivatives, expecting to provide a general retrospect and prospect on tetralone derivatives.

Binding interaction of protoberberine alkaloids against acetylcholinesterase (AChE) using molecular dynamics simulations and QM/MM calculations

Acetylcholinesterase (AChE) plays a vital role in Alzheimer's disease (AD), which is one of the most common causes of dementia. Discovering new effective inhibitors against AChE activity is seen to be one of the effective approaches to reduce the suffering from AD. Protoberberine alkaloids isolated from natural resources have previously been reported as potent AChE inhibitors. In order to gain insights into how these alkaloids could inhibit AChE, berberine, palmatine, and cyclanoline were selected to investigate in terms of binding orientation and their key interactions with AChE using molecular docking and molecular dynamics simulations and quantum chemical calculations. The results revealed that the molecular dynamics structures of palmatine and berberine indicated that their equilibrated structures did not occupy the gorge but they slightly moved away from the catalytic site (CAS). For cyclanoline, the binding mode was quite different from those of donepezil and the other protoberberine alkaloids: it preferred to stay deeper in the CAS site. Interaction energies and residual interaction energies confirmed that the key interactions for palmatine and berberine were π-π interactions with Trp286 and Tyr341 and H-bond interactions with Tyr124. Cyclanoline formed π-π interactions with Trp86 and H-bonds to the amino acids in the CAS site. The results suggested the importance of aromaticity in the core structure and the flexibility of the core structure or the substituents in order to fit into the narrow gorge. The HOMO, LUMO, bioavailability, drug-likeness and pharmacokinetics were also predicted. The results obtained will be useful for further AD drug development.

A Comprehensive Review of Cholinesterase Modeling and Simulation

The present article reviews published efforts to study acetylcholinesterase and butyrylcholinesterase structure and function using computer-based modeling and simulation techniques. Structures and models of both enzymes from various organisms, including rays, mice, and humans, are discussed to highlight key structural similarities in the active site gorges of the two enzymes, such as flexibility, binding site location, and function, as well as differences, such as gorge volume and binding site residue composition. Catalytic studies are also described, with an emphasis on the mechanism of acetylcholine hydrolysis by each enzyme and novel mutants that increase catalytic efficiency. The inhibitory activities of myriad compounds have been computationally assessed, primarily through Monte Carlo-based docking calculations and molecular dynamics simulations. Pharmaceutical compounds examined herein include FDA-approved therapeutics and their derivatives, as well as several other prescription drug derivatives. Cholinesterase interactions with both narcotics and organophosphate compounds are discussed, with the latter focusing primarily on molecular recognition studies of potential therapeutic value and on improving our understanding of the reactivation of cholinesterases that are bound to toxins. This review also explores the inhibitory properties of several other organic and biological moieties, as well as advancements in virtual screening methodologies with respect to these enzymes.

Discovery of new TLR7 agonists by a combination of statistical learning-based QSAR, virtual screening, and molecular dynamics

Search for new antiviral medications has surged in the past two years due to the COVID-19 crisis. Toll-like receptor 7 (TLR7) is among one of the most important TLR proteins of innate immunity that is responsible for broad antiviral response and immune system control. TLR7 agonists, as both vaccine adjuvants and immune response modulators, are among the top drug candidates for not only our contemporary viral pandemic but also other diseases. The agonists of TLR7 have been utilized as vaccine adjuvants and antiviral agents. In this study, we hybridized a statistical learning-based QSAR model with molecular docking and molecular dynamics simulation to extract new antiviral drugs by drug repurposing of the DrugBank database. First, we manually curated a dataset consisting of TLR7 agonists. The molecular descriptors of these compounds were extracted, and feature engineering was done to restrict the number of features to 45. We applied a statistically inspired modification of the partial least squares (SIMPLS) method to build our QSAR model. In the next stage, the DrugBank database was virtually screened structurally using molecular docking, and the top compounds for the guanosine binding site of TLR were identified. The result of molecular docking was again screened by the ligand-based approach of QSAR to eliminate compounds that do not display strong EC₅₀ values by the previously trained model. We then subjected the final results to molecular dynamics simulation and compared our compounds with imiquimod (an FDA-approved TLR7 agonist) and compound 1 (the most active compound against TLR7 in vitro, EC₅₀ = 0.2 nM). Our results evidently demonstrate that cephalosporins and nucleotide analogues (especially acyclic nucleotide analogues such as adefovir and cidofovir) are computationally potent agonists of TLR7. We finally reviewed some publications about cephalosporins that, just like pieces of a puzzle, completed our conclusion.

Silver(I) complexes of 3-methoxy-4-hydroxybenzaldehyde thiosemicarbazones and triphenylphosphine: structural, cytotoxicity, and apoptotic studies

Novel silver(i) complexes of the type [AgCl(PPh3)2(L)] {PPh3 = triphenylphosphine; L = VTSC = 3-methoxy-4-hydroxybenzaldehyde thiosemicarbazone (1); VMTSC = 3-methoxy-4-[2-(morpholine-1-yl)ethoxy]benzaldehyde thiosemicarbazone (2); VPTSC = 3-methoxy-4-[2-(piperidine-1-yl)ethoxy]benzaldehyde thiosemicarbazone (3)} were synthesized and fully characterized by spectroscopic techniques. The molecular structures of complexes 2 and 3 were determined by single crystal X-ray diffraction. Compounds 1-3 exhibited appreciable cytotoxic activity against human tumor cells (lung A549, breast MDA-MB-231 and MCF-7) with IC50 values in 48 h of incubation ranging from 5.6 to 18 μM. Cellular uptake studies showed that complexes 1-3 were efficiently internalized after 3 hours of treatment in MDA-MB-231 cells. The effects of complex 1 on the cell morphology, cell cycle, induction of apoptosis, mitochondrial membrane potential (Δψm), and reactive oxygen species (ROS) production have been evaluated in triple negative breast cancer (TNBC) cells MDA-MB-231. Our results showed that complex 1 induced typical morphological alterations of cell death, an increase in cells at the sub-G1 phase, apoptosis, and mitochondrial membrane depolarization. Furthermore, DNA binding studies evidenced that 1 can bind to ct-DNA and does so without modifying the B-structure of the DNA, but that the binding is weak compared to that of Hoechst 33258.

Exploring the out of sight antigens of SARS-CoV-2 to design a candidate multi-epitope vaccine by utilizing immunoinformatics approaches

SARS-CoV-2 causes a severe respiratory disease called COVID-19. Currently, global health is facing its devastating outbreak. However, there is no vaccine available against this virus up to now. In this study, a novel multi-epitope vaccine against SARS-CoV-2 was designed to provoke both innate and adaptive immune responses. The immunodominant regions of six non-structural proteins (nsp7, nsp8, nsp9, nsp10, nsp12 and nsp14) of SARS-CoV-2 were selected by multiple immunoinformatic tools to provoke T cell immune response. Also, immunodominant fragment of the functional region of SARS-CoV-2 spike (400-510 residues) protein was selected for inducing neutralizing antibodies production. The selected regions' sequences were connected to each other by furin-sensitive linker (RVRR). Moreover, the functional region of β-defensin as a well-known agonist for the TLR-4/MD complex was added at the N-terminus of the vaccine using (EAAAK)3 linker. Also, a CD4 + T-helper epitope, PADRE, was used at the C-terminal of the vaccine by GPGPG and A(EAAAK)2A linkers to form the final vaccine construct. The physicochemical properties, allergenicity, antigenicity, functionality and population coverage of the final vaccine construct were analyzed. The final vaccine construct was an immunogenic, non-allergen and unfunctional protein which contained multiple CD8 + and CD4 + overlapping epitopes, IFN-γ inducing epitopes, linear and conformational B cell epitopes. It could form stable and significant interactions with TLR-4/MD according to molecular docking and dynamics simulations. Global population coverage of the vaccine for HLA-I and II were estimated 96.2% and 97.1%, respectively. At last, the final vaccine construct was reverse translated to design the DNA vaccine. Although the designed vaccine exhibited high efficacy in silico, further experimental validation is necessary.