Discovery of novel series of 2-substituted benzo[d]oxazol-5-amine derivatives as multi-target directed ligands for the treatment of Alzheimer's disease

Morin attenuated the global cerebral ischemia via antioxidant, anti-inflammatory, and antiapoptotic mechanisms in rats

Global cerebral ischemia is one of the major causes of memory and cognitive impairment. Hyperactivation of acetylcholine esterase (AChE), oxidative stress, and inflammation are reported to cause memory and cognitive impairment in global cerebral ischemia. Morin, a flavonoid, is reported to have neuroprotective properties through its antioxidant and anti-inflammatory in multiple neurological diseases. However, its neuroprotective effects and memory and cognition enhancement have not yet been investigated. In the present study, we have determined the memory and cognition, and neuroprotective activity of Morin in bilateral common carotid artery occlusion and reperfusion (BCCAO/R) in Wistar rats. We found that Morin treatment significantly improved motor performance like grip strength and rotarod. Further, Morin improved memory and cognition in BCCAO rats by decreasing the AchE enzyme activity and enhancing the acetylcholine (Ach) levels. Additionally, Morin exhibited neuroprotection by ameliorating oxidative stress, neuroinflammation, and apoptosis in BCCAO rats. These findings confirm that Morin could enhance memory and cognition by ameliorating AchE activity, oxidative stress, neuroinflammation, and apoptosis in global cerebral ischemia. Therefore, Morin could be a promising neuroprotective and memory enhancer against global cerebral ischemic injury.

Indole-3 Carbinol and Diindolylmethane Mitigated β-Amyloid-Induced Neurotoxicity and Acetylcholinesterase Enzyme Activity: In Silico, In Vitro, and Network Pharmacology Study

Background: Alzheimer's disease (AD) is a neurodegenerative disease characterized by beta-amyloid (Aβ) deposition and increased acetylcholinesterase (AchE) enzyme activities. Indole 3 carbinol (I3C) and diindolylmethane (DIM) are reported to have neuroprotective activities against various neurological diseases, including ischemic stroke, Parkinson's disease, neonatal asphyxia, depression, stress, neuroinflammation, and excitotoxicity, except for AD. In the present study, we have investigated the anti-AD effects of I3C and DIM. Methods: Docking and molecular dynamic studies against AchE enzyme and network pharmacological studies were conducted for I3C and DIM. I3C and DIM's neuroprotective effects against self and AchE-induced Aβ aggregation were investigated. The neuroprotective effects of I3C and DIM against Aβ-induced neurotoxicity were assessed in SH-S5Y5 cells by observing cell viability and ROS. Results: Docking studies against AchE enzyme with I3C and DIM show binding efficiency of -7.0 and -10.3, respectively, and molecular dynamics studies revealed a better interaction and stability between I3C and AchE and DIM and AchE. Network pharmacological studies indicated that I3C and DIM interacted with several proteins involved in the pathophysiology of AD. Further, I3C and DIM significantly inhibited the AchE (IC50: I3C (18.98 µM) and DIM (11.84 µM)) and self-induced Aβ aggregation. Both compounds enhanced the viability of SH-S5Y5 cells that are exposed to Aβ and reduced ROS. Further, I3C and DIM show equipotential neuroprotection when compared to donepezil. Conclusions: Our findings indicate that both I3C and DIM show anti-AD effects by inhibiting the Aβ induced neurotoxicity and AchE activities.

Benzimidazole and Benzoxazole Derivatives Against Alzheimer's Disease

Benzimidazole and benzoxazole derivatives are included in the category of medical drugs in a wide range of areas such as anticancer, anticoagulant, antihypertensive, anti- inflammatory, antimicrobial, antiparasitic, antiviral, antioxidant, immunomodulators, proton pump inhibitors, hormone modulators, etc. Many researchers have focused on synthesizing more effective benzimidazole and benzoxazole derivatives for screening various biological activities. In addition, there are benzimidazole and benzoxazole rings as bioisosteres of aromatic rings found in drugs used in the treatment of Alzheimer's disease. Because of the diverse activity of the benzimidazole and benzoxazole rings and bioisosteres marketed as drugs for Alzheimer Diseases, designed compounds containing these rings are likely to be effective against Alzheimer's disease. In this study, the effectiveness of compounds containing benzimidazole and benzoxazole rings against Alzheimer's disease will be examined.

Design, synthesis, and biological evaluation of some 2-(3-oxo-5,6-diphenyl-1,2,4-triazin-2(3H)-yl)-N-phenylacetamide hybrids as MTDLs for Alzheimer's disease therapy

Inspite of established symptomatic relief drug targets, a multi targeting approach is highly in demand to cure Alzheimer's disease (AD). Simultaneous inhibition of cholinesterase (ChE), β secretase-1 (BACE-1) and Dyrk1A could be promising in complete cure of AD. A series of 18 diaryl triazine based molecular hybrids were successfully designed, synthesized, and tested for their hChE, hBACE-1, Dyrk1A and Aβ aggregation inhibitory potentials. Compounds S-11 and S-12 were the representative molecules amongst the series with multi-targeted inhibitory effects. Compound S-12 showed hAChE inhibition (IC50 value = 0.486 ± 0.047 μM), BACE-1 inhibition (IC50 value = 0.542 ± 0.099 μM) along with good anti-Aβ aggregation effects in thioflavin-T assay. Only compound S-02 of the series has shown Dyrk1A inhibition (IC50 value = 2.000 ± 0.360 μM). Compound S-12 has also demonstrated no neurotoxic liabilities against SH-SY5Y as compared to donepezil. The in vivo behavioral studies of the compound S-12 in the scopolamine- and Aβ-induced animal models also demonstrated attanuation of learning and memory functions in rats models having AD-like characteristics. The ex vivo studies, on the rat hippocampal brain demonstrated reduction in certain biochemical markers of the AD brain with a significant increase in ACh level. The Western blot and Immunohistochemistry further revealed lower tau, APP and BACE-1 molecular levels. The drosophilla AD model also revealed improved eyephenotype after treatment with compound S-12. The molecular docking studies of the compounds suggested that compound S-12 was interacting with the ChE-PAS & CAS residues and catalytic dyad residues of the BACE-1 enzymes. The 100 ns molecular dynamics simulation studies of the ligand-protein complexed with hAChE and hBACE-1 also suggested stable ligand-protein confirmation throughout the simulation run.

Development of multi-targetable chalcone derivatives bearing N-aryl piperazine moiety for the treatment of Alzheimer's disease

The multi-target directed ligand (MTDL) discovery has been gaining immense attention in the development of therapeutics for Alzheimer's disease (AD). The strategy has been evolved as an auspicious approach suitable to combat the heterogeneity and the multifactorial nature of AD. Therefore, multi-targetable chalcone derivatives bearing N-aryl piperazine moiety were designed, synthesized, and evaluated for the treatment of AD. All the synthesized compounds were screened for thein vitro activityagainst acetylcholinesterase (AChE), butylcholinesterase (BuChE), β-secretase-1 (BACE-1), and inhibition of amyloid β (Aβ) aggregation. Amongst all the tested derivatives, compound 41bearing unsubstituted benzylpiperazine fragment and para-bromo substitution at the chalcone scaffold exhibited balanced inhibitory profile against the selected targets. Compound 41 elicited favourable permeation across the blood-brain barrier in the PAMPA assay. The molecular docking and dynamics simulation studies revealed the binding mode analysis and protein-ligand stability ofthe compound with AChE and BACE-1. Furthermore,itameliorated cognitive dysfunctions and signified memory improvement in thein-vivobehavioural studies (scopolamine-induced amnesia model). Theex vivobiochemical analysis of mice brain homogenates established the reduced AChE and increased ACh levels. The antioxidant activity of compound 41 was accessed with the determination of catalase (CAT) and malondialdehyde (MDA) levels. The findings suggested thatcompound 41, containing a privileged chalcone scaffold, can act as a lead molecule for developing AD therapeutics.

Tangeretin confers neuroprotection, cognitive and memory enhancement in global cerebral ischemia in rats

Global cerebral ischemia is commonly associated with neurological deficits, including cognitive and memory impairments. The present study aims to investigate the neuroprotective, cognitive, and memory enhancement effects of Tangeretin, a flavonoid against global cerebral ischemia in rats. Bilateral common carotid artery occlusion (BCCAO) and reperfusion injury method was used to induce global cerebral ischemia in rats. Motor, cognitive, and memory functions were evaluated using rotarod, grip strength, Y-maze, and Morris water maze. Further, acetylcholine esterase (AchE) enzyme activity, acetylcholine (Ach), oxidative stress markers (ROS, SOD, MDA, and CAT), inflammation (IL-6 and TNF-α), and apoptotic markers (cytochrome C, caspase 9, and caspase 3) in BCCAO rats were measured following Tangeretin (5,10, and 20 mg/kg, oral) treatment. Our findings show that Tangeretin treatment significantly improved cognition and memory by enhancing Ach levels through the amelioration of AchE enzyme activity in BCCAO rats. Moreover, Tangeretin exhibited neuroprotective effects through the mitigation of oxidative stress, inflammation, and apoptosis in the BCCAO rats. In summary, the current findings suggested that Tangeretin exhibited neuroprotection, cognitive and memory enhancement against global cerebral ischemia.

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

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

Novel alkyl-substituted 4-methoxy benzaldehyde thiosemicarbazones: Multi-target directed ligands for the treatment of Alzheimer's disease

Alzheimer's disease (AD) is a devastating neurodegenerative disorder affecting mental ability and interrupts neurocognitive functions. Treating multifactorial conditions of AD with a single-target-directed drug is highly difficult. Thus, a multi-target-directed ligand (MTDL) development strategy has been developed as a promising approach for the treatment of AD. Herein, we have synthesized two novel thiosemicarbazones as MTDLs and reported their bioactivities against diverse neuropathological events involved in AD. In vitro studies revealed that both compounds exhibited promising anticholinesterase activity (AChE, IC50 = 15.98 μM, MZET and IC50 = 30.23 μM, MZMT), well supported by a detailed computational study. Both analogs have shown good thermodynamic behaviour and stability through interactions with characteristic amino acid residues throughout simulation of 100 ns against acetylcholinesterase enzyme. In an electrophysiology assay, these analogs have shown a characteristic inhibitory response against the GluN1-1a + GluN2B subunit of N-methyl-D-aspartate receptors. Pre-treatment of BV-2 microglial cells with MZET effectively decreased nitrite production compared to nitrite produced by lipopolysaccharide-treated cells alone. Further, the effect of MZMT and MZET on autophagy regulation was determined using stably transfected SH-SY5Y neuroblastoma cells. MZET significantly enhanced the autophagy flux in neuroblastoma cells. A significant decrease in copper-catalysed oxidation of amyloid-β in presence of synthesized thiosemicarbazones was also observed. Collectively, our findings indicated that these analogs have potential as effective anti-AD candidates and can be used as a prototype to develop more safer multi-targeted anti-AD drugs.

WNT-β Catenin Signaling as a Potential Therapeutic Target for Neurodegenerative Diseases: Current Status and Future Perspective

Wnt/β-catenin (WβC) signaling pathway is an important signaling pathway for the maintenance of cellular homeostasis from the embryonic developmental stages to adulthood. The canonical pathway of WβC signaling is essential for neurogenesis, cell proliferation, and neurogenesis, whereas the noncanonical pathway (WNT/Ca²⁺ and WNT/PCP) is responsible for cell polarity, calcium maintenance, and cell migration. Abnormal regulation of WβC signaling is involved in the pathogenesis of several neurodegenerative diseases such as Alzheimer's disease (AD), Parkinson's disease (PD), Huntington's disease (HD), amyotrophic lateral sclerosis (ALS), multiple sclerosis (MS), and spinal muscular atrophy (SMA). Hence, the alteration of WβC signaling is considered a potential therapeutic target for the treatment of neurodegenerative disease. In the present review, we have used the bibliographical information from PubMed, Google Scholar, and Scopus to address the current prospects of WβC signaling role in the abovementioned neurodegenerative diseases.

Palladium-Catalyzed Synthesis, Acetylcholinesterase Inhibition, and Neuroprotective Activities of N-Aryl Galantamine Analogues

A series of new N-aryl galantamine analogues (5a-5x) were designed and synthesized by modification of galantamine, using Pd-catalyzed Buchwald-Hartwig cross-coupling reaction in good to excellent yields. The cholinesterase inhibitory and neuroprotective activities of N-aryl derivatives of galantamine were evaluated. Among the synthesized compounds, the 4-methoxylpyridine-galantamine derivative (5q) (IC₅₀ = 0.19 μM) exhibited excellent acetylcholinesterase inhibition activity, as well as significant neuroprotective effect against H₂O₂-induced injury in SH-SY5Y cells. Molecular docking, staining, and Western blotting analyses were performed to demonstrate the mechanism of action of 5q. Derivative 5q would be a promising multifunctional lead compound for the treatment of Alzheimer's disease.

G, Krishnamurthy S, Chaurasia RN, Shrivastava SK. Development and Evaluation of Some Molecular Hybrids of N-(1-Benzylpiperidin-4-yl)-2-((5-phenyl-1,3,4-oxadiazol-2-yl)thio) as Multifunctional Agents to Combat Alzheimer's Disease

A series of some novel compounds (SD-1-17) were designed following a molecular hybridization approach, synthesized, and biologically tested for hAChE, hBChE, hBACE-1, and Aβ aggregation inhibition potential to improve cognition and memory functions associated with Alzheimer's disease. Compounds SD-4 and SD-6 have shown multifunctional inhibitory profiles against hAChE, hBChE, and hBACE-1 enzymes in vitro. Compounds SD-4 and SD-6 have also shown anti-Aβ aggregation potential in self- and acetylcholinesterase (AChE)-induced thioflavin T assay. Both compounds have shown a significant propidium iodide (PI) displacement from the cholinesterase-peripheral active site (ChE-PAS) region with excellent blood-brain barrier (BBB) permeability and devoid of neurotoxic liabilities. Compound SD-6 ameliorates cognition and memory functions in scopolamine- and Aβ-induced behavioral rat models of Alzheimer's disease (AD). Ex vivo biochemical estimation revealed a significant decrease in malonaldehyde (MDA) and AChE levels, while a substantial increase of superoxide dismutase (SOD), catalase, glutathione (GSH), and ACh levels is seen in the hippocampal brain homogenates. The histopathological examination of brain slices also revealed no sign of neuronal or any tissue damage in the SD-6-treated experimental animals. The in silico molecular docking results of compounds SD-4 and SD-6 showed their binding with hChE-catalytic anionic site (CAS), PAS, and the catalytic dyad residues of the hBACE-1 enzymes. A 100 ns molecular dynamic simulation study of both compounds with ChE and hBACE-1 enzymes also confirmed the ligand-protein complex's stability, while quikprop analysis suggested drug-like properties of the compounds.

Discovery of multi-target directed 3-OH pyrrolidine derivatives through a semisynthetic approach from alkaloid vasicine for the treatment of Alzheimer's disease

Vasicine is a pyrroloquinazoline alkaloid, which has been isolated from the plant Adhatoda vasica. Naturally inspired semi-synthetic transformations were prepared using vasicine as a synthetic precursor to overcome Alzheimer's disease (AD). These semi-synthetic analogs exhibited stable interactions and were well resided at AChE and BChE active sites in in-silico studies. Further, in-vitro experiments were performed to assess the cholinesterase inhibitory activity and reduction of amyloid-beta (Aβ_1-42) plaques potency, PAMPA assay permeability, and antioxidant activity, these findings suggested that compound VA10 can be a lead molecule among all the synthesized analogs. The compound VA10 binds towards AChE peripheral anionic site (PAS) property was established through propidium iodide displacement assay. Moreover, VA10 showed no notable cytotoxicity and exhibited neuroprotective nature on Aβ_1-42 treated SH-SY5Y cell line. In addition, VA10 was found to be safe in rats, which was confirmed by acute oral toxicity studies. Furthermore, in-vivo studies suggested that compound VA10 (10 mg/kg, p.o) ameliorated the memory and cognition impairment in scopolamine-induced amnesia model and Aβ_1-42 induced Alzheimer rat model. Ex-vivo studies of compound VA10 demonstrate improved ACh levels by inhibiting AChE activity in rat brain. Moreover, histopathological observations on rats brain sections indicate VA10 (10 mg/kg, p.o) recovered the neuronal cells at hippocampus region (DG, CA3, and CA1). These positive experimental data from in-silico, in-vitro and in-vivo studies, suggested that compound VA10 can be a lead compound for further preclinical development studies as a naturally derived alkaloid for anti-AD.

Indene-Derived Hydrazides Targeting Acetylcholinesterase Enzyme in Alzheimer's: Design, Synthesis, and Biological Evaluation

As acetylcholinesterase (AChE) plays a crucial role in advancing Alzheimer's disease (AD), its inhibition is a promising approach for treating AD. Sulindac is an NSAID of the aryl alkanoic acid class, consisting of a indene moiety, which showed neuroprotective behavior in recent studies. In this study, newer Indene analogs were synthesized and evaluated for their in vitro AChE inhibition. Additionally, compared with donepezil as the standard drug, these Indene analogs were accessed for their cell line-based toxicity study on SH-SY5Y cell line. The molecule SD-30, having hydrogen bond donor (HBD) at para-position, showed maximum AChE inhibition potential (IC₅₀ 13.86 ± 0.163 µM) in the indene series. Further, the SD-30 showed maximum BuChE inhibition potential (IC₅₀ = 48.55 ± 0.136 µM) with a selectivity ratio of 3.50 and reasonable antioxidant properties compared to ascorbic acid (using DPPH assay). SD-30 (at a dose level: of 10 µM, 20 µM) effectively inhibited AChE-induced Aβ aggregation and showed no significant toxicity up to 30 mM against SH-SY5Y cell lines.

Preclinical Models for Alzheimer's Disease: Past, Present, and Future Approaches

A robust preclinical disease model is a primary requirement to understand the underlying mechanisms, signaling pathways, and drug screening for human diseases. Although various preclinical models are available for several diseases, clinical models for Alzheimer's disease (AD) remain underdeveloped and inaccurate. The pathophysiology of AD mainly includes the presence of amyloid plaques and neurofibrillary tangles (NFT). Furthermore, neuroinflammation and free radical generation also contribute to AD. Currently, there is a wide gap in scientific approaches to preventing AD progression. Most of the available drugs are limited to symptomatic relief and improve deteriorating cognitive functions. To mimic the pathogenesis of human AD, animal models like 3XTg-AD and 5XFAD are the primarily used mice models in AD therapeutics. Animal models for AD include intracerebroventricular-streptozotocin (ICV-STZ), amyloid beta-induced, colchicine-induced, etc., focusing on parameters such as cognitive decline and dementia. Unfortunately, the translational rate of the potential drug candidates in clinical trials is poor due to limitations in imitating human AD pathology in animal models. Therefore, the available preclinical models possess a gap in AD modeling. This paper presents an outline that critically assesses the applicability and limitations of the current approaches in disease modeling for AD. Also, we attempted to provide key suggestions for the best-fit model to evaluate potential therapies, which might improve therapy translation from preclinical studies to patients with AD.

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

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

Design, synthesis, and biological evaluation of novel (4-(1,2,4-oxadiazol-5-yl)phenyl)-2-aminoacetamide derivatives as multifunctional agents for the treatment of Alzheimer's disease

On the basis of our previous work, a novel series of (4-(1,2,4-oxadiazol-5-yl)phenyl)-2-aminoacetamide derivatives were synthesized and evaluated as multifunctional ligands for the treatment of Alzheimer's disease (AD). Biological evaluations indicated that the derivatives can be used as anti-AD drugs that have multifunctional properties, inhibit the activity of butyrylcholinesterase (BuChE), inhibit neuroinflammation, have neuroprotective properties, and inhibit the self-aggregation of Aβ. Compound f9 showed good potency in BuChE inhibition (IC₅₀: 1.28 ± 0.18 μM), anti-neuroinflammatory potency (NO, IL-1β, TNF-α; IC₅₀: 0.67 ± 0.14, 1.61 ± 0.21, 4.15 ± 0.44 μM, respectively), and inhibited of Aβ self-aggregation (51.91 ± 3.90%). Preliminary anti-inflammatory mechanism studies indicated that the representative compound f9 blocked the activation of the NF-κB signaling pathway. Moreover, f9 exhibited 1,1-Diphenyl-2-picrylhydrazyl (DPPH) radical scavenging effect, and an inhibitory effect on the production of intracellular reactive oxygen species (ROS). In the bi-directional transport assay, f9 displayed proper blood-brain barrier (BBB) permeability. In addition, the title compound improved memory and cognitive functions in a mouse model induced by scopolamine. Hence, the compound f9 can be considered as a promising lead compound for further investigation in the treatment of AD.

Improved machine learning scoring functions for identification of Electrophorus electricus's acetylcholinesterase inhibitors

Structure-based drug design (SBDD) is an important in silico technique, used for the identification of enzyme inhibitors. Acetylcholinesterase (AChE), obtained from Electrophorus electricus (ee), is widely used for the screening of AChE inhibitors. It shares structural homology with the AChE of human and other organisms. Till date, the three-dimensional crystal structure of enzyme from ee is not available that makes it challenging to use the SBDD approach for the identification of inhibitors. A homology model was developed for eeAChE in the present study, followed by its structural refinement through energy minimisation. The docking protocol was developed using a grid dimension of 84 × 66 × 72 and grid point spacing of 0.375 Å for eeAChE. The protocol was validated by redocking a set of co-crystallised inhibitors obtained from mouse AChE, and their interaction profiles were compared. The results indicated a poor performance of the Autodock scoring function. Hence, a batch of machine learning-based scoring functions were developed. The validation results displayed an accuracy of 81.68 ± 1.73% and 82.92 ± 3.05% for binary and multiclass classification scoring function, respectively. The regression-based scoring function produced [Formula: see text] and [Formula: see text] values of 0.94, 0.635 and 0.634, respectively.

Novel hydroxybenzylamine-deoxyvasicinone hybrids as anticholinesterase therapeutics for Alzheimer's disease

A series of novel 2-hydroxybenzylamine-deoxyvasicinone hybrid analogs (8a-8n) have been synthesized and evaluated as inhibitors of acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE), and as inhibitors of amyloid peptide (Aβ_1-42) aggregation, for treatment of Alzheimer's disease (AD). These dual acting compounds exhibited good AChE inhibitory activities ranging from 0.34 to 6.35 µM. Analogs8g and 8n were found to be the most potent AChE inhibitors in the series with IC₅₀values of 0.38 µM and 0.34 µM, respectively. All the analogs (8a-8n) exhibited weak BuChE inhibitory activities ranging from 14.60 to 21.65 µM. Analogs8g and 8n exhibited BuChE with IC₅₀values of 15.38 µM and 14.60 µM, respectively, demonstrating that these analogs were greater than 40-fold more selective for inhibition of AChE over BuChE. Additionally, compounds8g and 8n were also found to be the best inhibitors of self-induced Aβ_1-42 peptide aggregation with IC₅₀values of 3.91 µM and 3.22 µM, respectively; 8g and 8n also inhibited AChE-induced Aβ_1-42 peptide aggregation by 68.7% and 72.6%, respectively. Kinetic analysis and molecular docking studies indicate that analogs 8g and 8n bind to a new allosteric pocket (site B) on AChE. In addition, the observed inhibition of AChE-induced Aβ_1-42 peptide aggregation by 8n is likely due to allosteric inhibition of the binding of this peptide at the CAS site on AChE. Overall, these results indicate that 8g and 8n are examples of dual-acting lead compounds for the development of highly effective anti-AD drugs.

Biological activity of 3-(2-benzoxazol-5-yl)alanine derivatives

Searching for new drugs is still a challenge for science, mainly because of civilization development and globalization which promote the rapid spread of diseases, which is particularly dangerous in the case of infectious ones. Moreover, readily available already known antibiotics are often overused or misused, possibly contributing to the increase in the number of multidrug-resistant microorganisms. A consequence of this is the need for new structures of potential drugs. One of them is a benzoxazole moiety, a basic skeleton of a group of fluorescent heterocyclic compounds already widely used in chemistry, industry, and medicine, which is also present in naturally occurring biologically active compounds. Moreover, synthetic benzoxazoles are also biologically active. Considering all of that, a large group of non-proteinogenic amino acids based on 3-(2-benzoxazol-5-yl)alanine skeleton was studied in search for new antimicrobial and anticancer agents. Screening tests revealed that antibacterial potential of 41 compounds studied is not very high; however, they are selective acting only against Gram-positive bacteria (B. subtilis). Moreover, almost half of the studied compounds have antifungal properties, also against pathogens (C. albicans). Most of studied compounds are toxic to both normal and cancer cells. However, in a few cases, toxicity to normal cells is much lower than for cancer cells indicating these compounds as future anticancer agents. The research carried out on such a large group of compounds allowed to establish a structure–activity relationship which enables to select candidates for further modifications, necessary to improve their biological activity and obtain a new lead structure with potential for therapeutic use.

Neuroprotective effects of quercetin produced by an endophytic fungus Nigrospora oryzae isolated from Tinospora cordifolia

AIMS

Alzheimer's disease is considered one of the most prevalent neurodegenerative disorders and dementia is the core symptom of this disease. This study was aimed to test the bioactive compounds produced by endophytic fungus for the inhibition of acetylcholinesterase (AChE) activity and to identify the compound responsible for this activity.

METHODS AND RESULTS

Endophytic fungi were isolated from the medicinal plant Tinospora cordifolia and screened for AChE inhibition and antioxidant activity. The extract of one of the isolates Nigrospora oryzae (GL15) showed maximum AChE inhibition as well as antioxidant activity. The compound responsible for AChE inhibition (fraction 3) was identified as quercetin based on UV, FTIR spectra, HPLC and ESI-MS analyses. Furthermore, the identification of quercetin in the extract of fraction 3 was confirmed by ¹ H NMR analysis. This extract showed anti-dementia-like activity in scopolamine (SCO) model. The minimal effective dose of the extract of fraction 3 modulated the SCO-provoked cognitive deficits such as impairments in spatial recognition memory and latency period in Y-maze test and passive avoidance test, respectively. The SCO-induced modulation in cholinergic pathway was ameliorated by the extract of N. oryzae in hippocampus, resulting in decrease in AChE activity and restoration of cytoarchitecture of hippocampus.

CONCLUSIONS

The bioactive compound quercetin produced by N. oryzae may cure the learning and memory shortfalls via AChE-mediated mechanism in experimental mice.

SIGNIFICANCE AND IMPACT OF THE STUDY

The endophytic fungus N. oryzae serves as a potential source for the bioactive compound quercetin, which plays an important role in the management of Alzheimer's disease.