Inhibition of β-site amyloid precursor protein cleaving enzyme 1 and cholinesterases by pterosins via a specific structure-activity relationship with a strong BBB permeability

Ferroptosis regulation through Nrf2 and implications for neurodegenerative diseases

This article provides an overview of the background knowledge of ferroptosis in the nervous system, as well as the key role of nuclear factor E2-related factor 2 (Nrf2) in regulating ferroptosis. The article takes Alzheimer's disease (AD), Parkinson's disease (PD), Huntington's disease (HD), and amyotrophic lateral sclerosis (ALS) as the starting point to explore the close association between Nrf2 and ferroptosis, which is of clear and significant importance for understanding the mechanism of neurodegenerative diseases (NDs) based on oxidative stress (OS). Accumulating evidence links ferroptosis to the pathogenesis of NDs. As the disease progresses, damage to the antioxidant system, excessive OS, and altered Nrf2 expression levels, especially the inhibition of ferroptosis by lipid peroxidation inhibitors and adaptive enhancement of Nrf2 signaling, demonstrate the potential clinical significance of Nrf2 in detecting and identifying ferroptosis, as well as targeted therapy for neuronal loss and mitochondrial dysfunction. These findings provide new insights and possibilities for the treatment and prevention of NDs.

Development of Potential Multi-Target Inhibitors for Human Cholinesterases and Beta-Secretase 1: A Computational Approach

Alzheimer's disease causes chronic neurodegeneration and is the leading cause of dementia in the world. The causes of this disease are not fully understood but seem to involve two essential cerebral pathways: cholinergic and amyloid. The simultaneous inhibition of AChE, BuChE, and BACE-1, essential enzymes involved in those pathways, is a promising therapeutic approach to treat the symptoms and, hopefully, also halt the disease progression. This study sought to identify triple enzymatic inhibitors based on stereo-electronic requirements deduced from molecular modeling of AChE, BuChE, and BACE-1 active sites. A pharmacophore model was built, displaying four hydrophobic centers, three hydrogen bond acceptors, and one positively charged nitrogen, and used to prioritize molecules found in virtual libraries. Compounds showing adequate overlapping rates with the pharmacophore were subjected to molecular docking against the three enzymes and those with an adequate docking score (n = 12) were evaluated for physicochemical and toxicological parameters and commercial availability. The structure exhibiting the greatest inhibitory potential against all three enzymes was subjected to molecular dynamics simulations (100 ns) to assess the stability of the inhibitor-enzyme systems. The results of this in silico approach indicate ZINC1733 can be a potential multi-target inhibitor of AChE, BuChE, and BACE-1, and future enzymatic assays are planned to validate those results.

Evaluation of berberine nanoparticles as a strategy to modulate acetylcholinesterase activity

Researchers have concentrated efforts in the search for natural-based reversible inhibitors for cholinesterase enzymes as they may play a key role in the treatment of degenerative diseases. Diverse plant alkaloids can inhibit the action of acetylcholinesterase and, among them, berberine is a promising bioactive. However, berberine has poor water solubility and low bioavailability, which makes it difficult to use in treatment. The solid dispersion technique can improve the water affinity of hydrophobic substances, but berberine solid dispersions have not been extensively studied. Safety testing is also essential to ensure that the berberine-loaded solid dispersions are safe for use. This study investigated the effectiveness of berberine-loaded solid dispersions (SD) as inhibitors of acetylcholinesterase enzyme (AChE). Docking simulation was used to investigate the influence of berberine on AChE, and in vitro assays were conducted to confirm the enzymatic kinetics of AChE in the presence of berberine. Berberine SD also showed improved cytotoxic effects on tumoral cells when dispersed in aqueous media. In vivo assays using Allium cepa were implemented, and no cytotoxicity/genotoxicity was found for the berberine solid dispersion. These results suggest that berberine SD could be a significant step towards safe nanostructures for use in the treatment of neurodegenerative diseases.

The neurobiology and therapeutic potential of multi-targeting β-secretase, glycogen synthase kinase 3β and acetylcholinesterase in Alzheimer's disease

Alzheimer's Disease (AD) is the most common form of dementia, affecting almost 50 million of people around the world, characterized by a complex and age-related progressive pathology with projections to duplicate its incidence by the end of 2050. AD pathology has two major hallmarks, the amyloid beta (Aβ) peptides accumulation and tau hyperphosphorylation, alongside with several sub pathologies including neuroinflammation, oxidative stress, loss of neurogenesis and synaptic dysfunction. In recent years, extensive research pointed out several therapeutic targets which have shown promising effects on modifying the course of the disease in preclinical models of AD but with substantial failure when transposed to clinic trials, suggesting that modulating just an isolated feature of the pathology might not be sufficient to improve brain function and enhance cognition. In line with this, there is a growing consensus that an ideal disease modifying drug should address more than one feature of the pathology. Considering these evidence, β-secretase (BACE1), Glycogen synthase kinase 3β (GSK-3β) and acetylcholinesterase (AChE) has emerged as interesting therapeutic targets. BACE1 is the rate-limiting step in the Aβ production, GSK-3β is considered the main kinase responsible for Tau hyperphosphorylation, and AChE play an important role in modulating memory formation and learning. However, the effects underlying the modulation of these enzymes are not limited by its primarily functions, showing interesting effects in a wide range of impaired events secondary to AD pathology. In this sense, this review will summarize the involvement of BACE1, GSK-3β and AChE on synaptic function, neuroplasticity, neuroinflammation and oxidative stress. Additionally, we will present and discuss new perspectives on the modulation of these pathways on AD pathology and future directions on the development of drugs that concomitantly target these enzymes.

A rhein-huprine hybrid protects erythrocyte membrane integrity against Alzheimer's disease related Aβ(1-42) peptide

Alzheimer's disease remains largely unknown, and currently there is no complete cure for the disease. New synthetic approaches have been developed to create multi-target agents, such as RHE-HUP, a rhein-huprine hybrid which can modulate several biological targets that are relevant to the development of the disease. While RHE-HUP has shown in vitro and in vivo beneficial effects, the molecular mechanisms by which it exerts its protective effect on cell membranes have not been fully clarified. To better understand RHE-HUP interactions with cell membranes, we used synthetic membrane models and natural models of human membranes. For this purpose, human erythrocytes and molecular model of its membrane built-up of dimyristoylphosphatidylcholine (DMPC) and dimyristoylphosphatidylethanolamine (DMPE) were used. The latter correspond to classes of phospholipids present in the outer and inner monolayers of the human erythrocyte membrane, respectively. X-ray diffraction and differential scanning calorimetry (DSC) results indicated that RHE-HUP was able to interact mainly with DMPC. In addition, scanning electron microscopy (SEM) analysis showed that RHE-HUP modified the normal biconcave shape of erythrocytes inducing the formation of echinocytes. Moreover, the protective effect of RHE-HUP against the disruptive effect of Aβ(1-42) on the studied membrane models was tested. X-ray diffraction experiments showed that RHE-HUP induced a recovery in the ordering of DMPC multilayers after the disruptive effect of Aβ(1-42), confirming the protective role of the hybrid.

Pterosin sesquiterpenoids from Pteris laeta Wall. ex Ettingsh. protect cells from glutamate excitotoxicity by modulating mitochondrial signals

ETHNOPHARMACOLOGICAL RELEVANCE

The genus Pteris (Pteridaceae) has been used as a traditional herb for a long time. In particular, Pteris laeta Wall. ex Ettingsh. has been widely used in traditional Chinese medicine to treat nervous system diseases and some pterosin sesquiterpenes from Pteris show neuroprotective activity, but their underlying molecular mechanisms remain elusive. Therefore, to investigate the neuroprotective activity and working mechanism of pterosin sesquiterpenes from P. laeta Wall. ex Ettingsh. will provide a better understanding and guidance in using P. laeta Wall. ex Ettingsh. as a traditional Chinese medicine.

AIM OF THE STUDY

We aim to develop effective treatments for neurodegenerative diseases from pterosin sesquiterpenes by evaluating their neuroprotective activity and investigating their working mechanisms.

MATERIALS AND METHODS

Primary screening on the glutamate-induced excitotoxicity cell model was assessed by 3-(4,5-Dimethylthiazol-2-yl)-2,5-Diphenyltetrazolium Bromide (MTT) assay. Fluorescent-activated cell sorting (FACS) was used to analyze the activation level of glutamate receptors and mitochondria membrane potential after treatment. Transcriptomics and proteomics analysis was performed to identify possible targets of pterosin B. The key pathways were enriched by the Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis through the Database for Annotation, Visualization, and Integrated Discovery (DAVID). The core targets were visualized by a protein-protein interaction network using STRING. The mRNA and protein expressions were evaluated using real-time quantitative polymerase chain reaction (Q-PCR) and western blot, respectively. Immunocytochemistry was performed to monitor mitochondrial and apoptotic proteins. Cellular reactive oxygen species (ROS) were measured by ROS assay, and Ca²⁺ was stained with Fluo-4 AM to quantify intracellular Ca²⁺ levels.

RESULTS

We found pterosin B from Pteris laeta Wall. ex Ettingsh. showed significant neuroprotective activity against glutamate excitotoxicity, enhancing cell viability from 43.8% to 105% (p-value: <0.0001). We demonstrated that pterosin B worked on the downstream signaling pathways of glutamate excitotoxicity rather than directly blocking the activation of glutamate receptors. Pterosin B restored mitochondria membrane potentials, alleviated intracellular calcium overload from 107.4% to 95.47% (p-value: 0.0006), eliminated cellular ROS by 36.55% (p-value: 0.0143), and partially secured cells from LPS-induced inflammation by increasing cell survival from 46.75% to 58.5% (p-value: 0.0114). Notably, pterosin B enhanced the expression of nuclear factor-erythroid factor 2-related factor 2 (NRF2) and heme oxygenase-1 (HO-1) by 2.86-fold (p-value: 0.0006) and 4.24-fold (p-value: 0.0012), and down-regulated Kelch-like ECH-associated protein 1 (KEAP1) expression by 2.5-fold (p-value: 0.0107), indicating that it possibly promotes mitochondrial biogenesis and mitophagy to maintain mitochondria quality control and homeostasis, and ultimately inhibits apoptotic cell death.

CONCLUSIONS

Our work revealed that pterosin B protected cells from glutamate excitotoxicity by targeting the downstream mitochondrial signals, making it a valuable candidate for developing potential therapeutic agents in treating neurodegenerative diseases.

Identification of BACE-1 Inhibitors against Alzheimer’s Disease through E-Pharmacophore-Based Virtual Screening and Molecular Dynamics Simulation Studies: An Insilco Approach

Alzheimer is a severe memory and cognitive impairment neurodegenerative disease that is the most common cause of dementia worldwide and characterized by the pathological accumulation of tau protein and amyloid-beta peptides. In this study, we have developed E-pharmacophore modeling to screen the eMolecules database with the help of a reported co-crystal structure bound with Beta-Site Amyloid Precursor Protein Cleaving Enzyme 1 (BACE-1). Flumemetamol, florbetaben, and florbetapir are currently approved drugs for use in the clinical diagnosis of Alzheimer’s disease. Despite the benefits of commercially approved drugs, there is still a need for novel diagnostic agents with enhanced physicochemical and pharmacokinetic properties compared to those currently used in clinical practice and research. In the E-pharmacophore modeling results, it is revealed that two aromatic rings (R19, R20), one donor (D12), and one acceptor (A8) are obtained, and also that similar pharmacophoric features of compounds are identified from pharmacophore-based virtual screening. The identified screened hits were filtered for further analyses using structure-based virtual screening and MM/GBSA. From the analyses, top hits such as ZINC39592220 and en1003sfl.46293 are selected based on their top docking scores (−8.182 and −7.184 Kcal/mol, respectively) and binding free energy (−58.803 and −56.951 Kcal/mol, respectively). Furthermore, a molecular dynamics simulation and MMPBSA study were performed, which revealed admirable stability and good binding free energy throughout the simulation period. Moreover, Qikprop results revealed that the selected, screened hits have good drug-likeness and pharmacokinetic properties. The screened hits ZINC39592220 and en1003sfl.46293 could be used to develop drug molecules against Alzheimer’s disease.

Pteris laeta Wall. and Its New Phytochemical, Pterosinsade A, Promote Hippocampal Neurogenesis via Activating the Wnt Signaling Pathway

Pteris laeta Wall., as a traditional tea, is popular in Southwest China, but its role in preventing cognitive impairment is unclear. In this study, Pteris laeta Wall. extracts (PW) and its active compounds were evaluated for preventive effects on Alzheimer's disease (AD) in vivo and in vitro. The results showed that PW diminished oxidative stress damage and apoptosis of Aβ-induced HT22 cells and also rescued cognitive deficits, and ameliorated pathological injury and inflammatory response in APP/PS1 mice. Besides, a new pterosin sesquiterpene, named pterosinsade A (PA), and nine known compounds were discovered from the EtOAc extract that possessed the best neuroprotective activity. PA reduced apoptosis of APP-overexpressing neural stem cells and promoted their proliferation and neuronal differentiation. Meanwhile, PW and PA promoted hippocampal neurogenesis, which proved to be associated with activating the Wnt signaling pathway. These findings suggest that PW and PA are candidates for AD prevention.

Dynamic genome evolution in a model fern

The large size and complexity of most fern genomes have hampered efforts to elucidate fundamental aspects of fern biology and land plant evolution through genome-enabled research. Here we present a chromosomal genome assembly and associated methylome, transcriptome and metabolome analyses for the model fern species Ceratopteris richardii. The assembly reveals a history of remarkably dynamic genome evolution including rapid changes in genome content and structure following the most recent whole-genome duplication approximately 60 million years ago. These changes include massive gene loss, rampant tandem duplications and multiple horizontal gene transfers from bacteria, contributing to the diversification of defence-related gene families. The insertion of transposable elements into introns has led to the large size of the Ceratopteris genome and to exceptionally long genes relative to other plants. Gene family analyses indicate that genes directing seed development were co-opted from those controlling the development of fern sporangia, providing insights into seed plant evolution. Our findings and annotated genome assembly extend the utility of Ceratopteris as a model for investigating and teaching plant biology.

Selected Natural Products in Neuroprotective Strategies for Alzheimer's Disease-A Non-Systematic Review

Neurodegenerative disorders such as Alzheimer’s disease (AD) are distinguished by the irreversible degeneration of central nervous system function and structure. AD is characterized by several different neuropathologies—among others, it interferes with neuropsychiatrical controls and cognitive functions. This disease is the number one neurodegenerative disorder; however, its treatment options are few and, unfortunately, ineffective. In the new strategies devised for AD prevention and treatment, the application of plant-based natural products is especially popular due to lesser side effects associated with their taking. Moreover, their neuroprotective activities target different pathological mechanisms. The current review presents the anti-AD properties of several natural plant substances. The paper throws light on products under in vitro and in vivo trials and compiles information on their mechanism of actions. Knowledge of the properties of such plant compounds and their combinations will surely lead to discovering new potent medicines for the treatment of AD with lesser side effects than the currently available pharmacological proceedings.

Improving ligand-ranking of AutoDock Vina by changing the empirical parameters

AutoDock Vina (Vina) achieved a very high docking-success rate, p ^ , but give a rather low correlation coefficient, R , for binding affinity with respect to experiments. This low correlation can be an obstacle for ranking of ligand-binding affinity, which is the main objective of docking simulations. In this context, we evaluated the dependence of Vina R coefficient upon its empirical parameters. R is affected more by changing the gauss2 and rotation than other terms. The docking-success rate p ^ is sensitive to the alterations of the gauss1, gauss2, repulsion, and hydrogen bond parameters. Based on our benchmarks, the parameter set1 has been suggested to be the most optimal. The testing study over 800 complexes indicated that the modified Vina provided higher correlation with experiment R set 1 = 0.556 ± 0.025 compared with R Default = 0.493 ± 0.028 obtained by the original Vina and R Vina 1.2 = 0.503 ± 0.029 by Vina version 1.2. Besides, the modified Vina can be also applied more widely, giving R ≥ 0.500 for 32/48 targets, compared with the default package, giving R ≥ 0.500 for 31/48 targets. In addition, validation calculations for 1036 complexes obtained from version 2019 of PDBbind refined structures showed that the set1 of parameters gave higher correlation coefficient ( R set 1 = 0.617 ± 0.017 ) than the default package ( R Default = 0.543 ± 0.020 ) and Vina version 1.2 ( R Vina 1.2 = 0.540 ± 0.020 ). The version of Vina with set1 of parameters can be downloaded at https://github.com/sontungngo/mvina. The outcomes would enhance the ranking of ligand-binding affinity using Autodock Vina.

Potential inhibitors for SARS-CoV-2 Mpro from marine compounds

Preventing the biological activity of SARS-CoV-2 main protease using natural compounds is of great interest. In this context, using a combination of AutoDock Vina and fast pulling of ligand simulations, eleven marine fungi compounds were identified that probably play as highly potent inhibitors for preventing viral replication. In particular, four compounds including M15 (3-O-(6-O-α-l-arabinopyranosyl)-β-d-glucopyranosyl-1,4-dimethoxyxanthone), M8 (wailupemycins H), M11 (cottoquinazolines B), and M9 (wailupemycins I) adopted the predicted ligand-binding free energy of −9.87, −9.82, −9.62, and −9.35 kcal mol⁻¹, respectively, whereas the other adopted predicted ligand-binding free energies in the range from −8.54 to −8.94 kcal mol⁻¹. The results were obtained using a combination of Vina and FPL simulations. Notably, although, AutoDock4 adopted higher accurate results in comparison with Vina, Vina is proven to be a more suitable technique for rapidly screening ligand-binding affinity with a large database of compounds since it requires much smaller computing resources. Furthermore, FPL is better than Vina to classify inhibitors upon ROC-AUC analysis.

Preventing the biological activity of SARS-CoV-2 main protease using natural compounds is of great interest.

Dual-target compounds for Alzheimer's disease: Natural and synthetic AChE and BACE-1 dual-inhibitors and their structure-activity relationship (SAR)

Alzheimer's disease (AD) is a chronic neurodegenerative disease and represents the major cause of dementia worldwide. Currently, there are no available treatments capable to deliver disease-modifying effects, and the available drugs can only alleviate the symptoms. The exact pathology of AD is not yet fully understood and several hallmarks such as the presence of amyloid-β (Aβ) senile plaques, neurofibrillary tangles (NFTs) as well as the loss of cholinergic function have been associated to AD. Distinct pharmacological targets have been validated to address AD, with acetylcholinesterase (AChE) and β-secretase-1 (BACE-1) being two of the most explored ones. A great deal of research has been devoted to the development of new AChE and BACE-1 effective inhibitors, tackled separately or in combination of both. The multi-factorial nature of AD conducted to the development of multi-target directed ligands (MTDLs), defined as single molecules capable to modulate more than one biological target, as an alternative approach to the old paradigm one-target one-drug. In this context, this review describes a collection of natural and synthetic compounds with dual-inhibitory properties towards both AChE and BACE-1 in the MTDLs context. Furthermore, this review also provides a critical comprehensive analysis of structure-activity relationships (SAR) of the synthetic compounds.

Current Quest in Natural Bioactive Compounds for Alzheimer's Disease: Multi-Targeted-Designed-Ligand Based Approach with Preclinical and Clinical Based Evidence

Alzheimer's disease is a common and most chronic neurological disorder (NDs) associated with cognitive dysfunction. Pathologically, Alzheimer's disease (AD) is characterized by the presence of β-amyloid (Aβ) plaques, hyper-phosphorylated tau proteins, and neurofibrillary tangles, however, persistence oxidative-nitrative stress, endoplasmic reticulum stress, mitochondrial dysfunction, inflammatory cytokines, pro-apoptotic proteins along with altered neurotransmitters level are common etiological attributes in its pathogenesis. Rivastigmine, memantine, galantamine, and donepezil are FDA approved drugs for symptomatic management of AD, whereas tacrine has been withdrawn because of hepatotoxic profile. These approved drugs only exert symptomatic relief and exhibit poor patient compliance. In the current scenario, the number of published evidence shows the neuroprotective potential of naturally occurring bioactive molecules via their antioxidant, anti-inflammatory, antiapoptotic and neurotransmitter modulatory properties. Despite their potent therapeutic implications, concerns have arisen in context to their efficacy and probable clinical outcome. Thus, to overcome these glitches, many heterocyclic and cyclic hydrocarbon compounds inspired by natural sources have been synthesized and showed improved therapeutic activity. Computational studies (molecular docking) have been used to predict the binding affinity of these natural bioactive as well as synthetic compounds derived from natural sources for the acetylcholine esterase, α/β secretase Nuclear Factor kappa- light-chain-enhancer of activated B cells (NF-kB), Nuclear factor erythroid 2-related factor 2(Nrf2) and other neurological targets. Thus, in this review, we have discussed the molecular etiology of AD, focused on the pharmacotherapeutics of natural products, chemical and pharmacological aspects and multi-targeted designed ligands (MTDLs) of synthetic and semisynthetic molecules derived from the natural sources along with some important on-going clinical trials.

Flavonoids-Macromolecules Interactions in Human Diseases with Focus on Alzheimer, Atherosclerosis and Cancer

Flavonoids, a class of polyphenols, consumed daily in our diet, are associated with a reduced risk for oxidative stress (OS)-related chronic diseases, such as cardiovascular disease, neurodegenerative diseases, cancer, and inflammation. The involvement of flavonoids with OS-related chronic diseases have been traditionally attributed to their antioxidant activity. However, evidence from recent studies indicate that flavonoids' beneficial impact may be assigned to their interaction with cellular macromolecules, rather than exerting a direct antioxidant effect. This review provides an overview of the recent evolving research on interactions between the flavonoids and lipoproteins, proteins, chromatin, DNA, and cell-signaling molecules that are involved in the OS-related chronic diseases; it focuses on the mechanisms by which flavonoids attenuate the development of the aforementioned chronic diseases via direct and indirect effects on gene expression and cellular functions. The current review summarizes data from the literature and from our recent research and then compares specific flavonoids' interactions with their targets, focusing on flavonoid structure-activity relationships. In addition, the various methods of evaluating flavonoid-protein and flavonoid-DNA interactions are presented. Our aim is to shed light on flavonoids action in the body, beyond their well-established, direct antioxidant activity, and to provide insights into the mechanisms by which these small molecules, consumed daily, influence cellular functions.

BACE1 and cholinesterase inhibitory activities of compounds from Cajanus cajan and Citrus reticulata: an in silico study

Alzheimer's disease (AD) is one of the major neurodegenerative diseases whose underlying risk factors are yet to be fully understood. However, reduced cellular level of cholinesterase, as well as formation and deposition of amyloid plaques (Aβ) are thought to play critical roles in the pathogenesis of AD. Therefore, increases in cholinergic transmitter levels via cholinesterase (ChE) inhibitors as well as inhibition of amyloid plaques formation and aggregation via beta secretase-1 (BACE1) inhibitors have been proposed as treatment for this disease. This study was aimed at investigating the BACE1 and ChE inhibitory properties of compounds from Cajanus cajan and Citrus reticulata based on their traditional connection with the management of neurodegenerative diseases, coupled with their protective effects on chemical-induced cognitive impairment. Using in silico methods, one hundred and nineteen compounds from C. cajan and C. reticulata were docked with acetylcholinesterase (AChE), butyrylcholinesterase (BChE), and BACE1 using Vina. Molecular interactions of the top-ranked compounds for the 3 protein targets were viewed with Discovery Studio, followed by characterization of their ADME properties using the Swiss online ADME web tool. Among the one hundred and ninety nine compounds screened, 3 compounds, genistin (76), naphthalen-2-yl-acetic acid, 6-hydroxy-6-methyl-cyclodecyl ester (94) and vitexin (119) have remarkable binding affinity for the three protein targets and passed the oral drugability test, while only naphthalen-2-yl-acetic acid, 6-hydroxy-6-methyl-cyclodecyl ester (94) exhibited BBB permeation property. Genistin and vitexin from C. cajan and naphthalen-2-yl-acetic acid, 6-hydroxy-6-methyl-cyclodecyl ester from C. reticulata possibly contributed, at least in part, to the neurotherapeutic potentials of these plants.

Unravelling the molecular basis of AM-6494 high potency at BACE1 in Alzheimer's disease: an integrated dynamic interaction investigation

β-amyloid precursor protein cleaving enzyme1 (BACE1) has prominently been an important drug design target implicated in Alzheimer's disease pathway. The failure rate of most of the already tested drugs at different clinical phases remains a major concern. Recently, AM-6494 was reported as a novel potent, highly selective, and orally effective inhibitor against BACE1. AM-6494 displayed no alteration of skin/fur colour in animal studies, an adverse effect common to previous BACE1 inhibitors. However, the atomistic molecular mechanism of BACE1 inhibition by AM-6494 remains unclear. To elucidate the binding mechanism of AM-6494 relative to umibecestat (CNP-520) as well as the structural changes when bound to BACE1, advanced computational techniques such as accelerated MD simulation and principal component analysis have been utilised. The results demonstrated higher binding affinity of AM-6494 at BACE1 with van der Waals as dominant energy contributor compared to umibecestat. Conformational monitoring of the β-hairpin flap covering the active site revealed an effective flap closure when bound with AM-6494 compared to CNP-520, which predominantly alternates between semi-open and closed conformations. The observed effective flap closure of AM-6494 explains its higher inhibitory power towards BACE1. Besides the catalytic Asp32/228 dyad, Tyr14, Leu30, Tyr71 and Gly230 represent critical residues in the potency of these inhibitors at BACE1 binding interface. The findings highlighted in this research provide a basis to explain AM-6494 high inhibitory potency and might assist in the design of new inhibitors with improved selectivity and potency for BACE1.

Synthesis of novel 4-methylthiocoumarin and comparison with conventional coumarin derivative as a multi-target-directed ligand in Alzheimer's disease

Alzheimer's disease (AD) is a multifactorial disorder characterized by cognitive deficit and memory loss. The pathological feature of the disease involves β-amyloid senile plaques, reduced levels of acetylcholine neurotransmitter, oxidative stress and neurofibrillary tangles formation within the brain of AD patients. The present study aims to screen the inhibitory activity of newly synthesized and existing novel 4-methylthiocoumarin derivative against acetylcholinesterase, butyrylcholinesterase, BACE1, β-amyloid aggregation and oxidative stress involved in the AD pathogenesis. The in vitro assays used in this study were Ellman's assay, FRET assays, Thioflavin T, transmission electron microscopy, circular dichroism, FRAP, and TEAC. Molecular docking and dynamics studies were performed to correlate the results. C3 and C7 (thiocoumarin derivatives) were found to be the most potent inhibitors of acetylcholinesterase (IC50-5.63 µM) and butyrylcholinesterase (IC50-3.40 µM) using Ellman's assays. Enzyme kinetic studies showed that C3 and C7 compounds followed by the mixed mode of inhibition using LB plot. C3 also moderately inhibited the BACE1 using FRET assay. C3 inhibited the fibrillization of β-amyloid peptides in a concentration-dependent manner as observed by Thioflavin T, TEM studies and Circular dichroism data. Molecular modeling studies were performed to understand the probable mode of binding of C3 and C7 in the binding pocket of acetylcholinesterase, butyrylcholinesterase, BACE1 and amyloid β peptides. This indicates the important role of hydrophobic interactions between C3 and acetylcholinesterase. C3 also exhibited significant antioxidant potential by FRAP and TEAC assays. Hence, C3 might serve as a promising lead for developing novel multi target-directed ligand for the treatment of AD.

Nrf2: a dark horse in Alzheimer's disease treatment

Alzheimer's disease (AD), an age-dependent neurodegenerative disorder, is the main cause of dementia. Common hallmarks of AD include the amyloid β-peptide (Aβ) aggregation, high levels of hyperphosphorylated tau protein (p-tau) and failure in redox homeostasis. To date, all proposed drugs affecting Aβ and/or p-tau have been failed in clinical trials. A decline in the expression of the transcription factor Nrf2 (nuclear factor-erythroid 2-p45 derived factor 2) and its driven genes (NQO1, HO-1, and GCLC), and alteration of the Nrf2-related pathways have been observed in AD brains. Nrf2 plays a critical role in maintaining cellular redox homeostasis and regulating inflammation response. Nrf2 activation also provides cytoprotection against increasing pathologies including neurodegenerative diseases. These lines of evidence imply that Nrf2 activation may be a novel AD treatment option. Interestingly, recent studies have also demonstrated that Nrf2 interferes with several key pathogenic processes in AD including Aβ and p-tau pathways. The current review aims to provide insights into the role of Nrf2 in AD. Also, we discuss the progress and challenges regarding the Nrf2 activators for AD treatment.

Synthesis, In Silico and In Vitro Evaluation of Some Flavone Derivatives for Acetylcholinesterase and BACE-1 Inhibitory Activity

Acetylcholinesterase (AChE) and β-secretase (BACE-1) have become attractive therapeutic targets for Alzheimer’s disease (AD). Flavones are flavonoid derivatives with various bioactive effects, including AChE and BACE-1 inhibition. In the present work, a series of 14 flavone derivatives was synthesized in relatively high yields (35–85%). Six of the synthetic flavones (B4, B5, B6, B8, D6 and D7) had completely new structures. The AChE and BACE-1 inhibitory activities were tested, giving pIC₅₀ 3.47–4.59 (AChE) and 4.15–5.80 (BACE-1). Three compounds (B3, D5 and D6) exhibited the highest biological effects on both AChE and BACE-1. A molecular docking investigation was conducted to explain the experimental results. These molecules could be employed for further studies to discover new structures with dual action on both AChE and BACE-1 that could serve as novel therapies for AD.

Synthesis, In Silico and In Vitro Evaluation for Acetylcholinesterase and BACE-1 Inhibitory Activity of Some N-Substituted-4-Phenothiazine-Chalcones

Acetylcholinesterase (AChE) and beta-secretase (BACE-1) are two attractive targets in the discovery of novel substances that could control multiple aspects of Alzheimer’s disease (AD). Chalcones are the flavonoid derivatives with diverse bioactivities, including AChE and BACE-1 inhibition. In this study, a series of N-substituted-4-phenothiazine-chalcones was synthesized and tested for AChE and BACE-1 inhibitory activities. In silico models, including two-dimensional quantitative structure–activity relationship (2D-QSAR) for AChE and BACE-1 inhibitors, and molecular docking investigation, were developed to elucidate the experimental process. The results indicated that 13 chalcone derivatives were synthesized with relatively high yields (39–81%). The bioactivities of these substances were examined with pIC₅₀ 3.73–5.96 (AChE) and 5.20–6.81 (BACE-1). Eleven of synthesized chalcones had completely new structures. Two substances AC4 and AC12 exhibited the highest biological activities on both AChE and BACE-1. These substances could be employed for further researches. In addition to this, the present study results suggested that, by using a combination of two types of predictive models, 2D-QSAR and molecular docking, it was possible to estimate the biological activities of the prepared compounds with relatively high accuracy.

Inhibition of Butyrylcholinesterase and Human Monoamine Oxidase-B by the Coumarin Glycyrol and Liquiritigenin Isolated from Glycyrrhiza uralensis

Eight compounds were isolated from the roots of Glycyrrhiza uralensis and tested for cholinesterase (ChE) and monoamine oxidase (MAO) inhibitory activities. The coumarin glycyrol (GC) effectively inhibited butyrylcholinesterase (BChE) and acetylcholinesterase (AChE) with IC₅₀ values of 7.22 and 14.77 µM, respectively, and also moderately inhibited MAO-B (29.48 µM). Six of the other seven compounds only weakly inhibited AChE and BChE, whereas liquiritin apioside moderately inhibited AChE (IC₅₀ = 36.68 µM). Liquiritigenin (LG) potently inhibited MAO-B (IC₅₀ = 0.098 µM) and MAO-A (IC₅₀ = 0.27 µM), and liquiritin, a glycoside of LG, weakly inhibited MAO-B (>40 µM). GC was a reversible, noncompetitive inhibitor of BChE with a K_i value of 4.47 µM, and LG was a reversible competitive inhibitor of MAO-B with a K_i value of 0.024 µM. Docking simulations showed that the binding affinity of GC for BChE (−7.8 kcal/mol) was greater than its affinity for AChE (−7.1 kcal/mol), and suggested that GC interacted with BChE at Thr284 and Val288 by hydrogen bonds (distances: 2.42 and 1.92 Å, respectively) beyond the ligand binding site of BChE, but that GC did not form hydrogen bond with AChE. The binding affinity of LG for MAO-B (−8.8 kcal/mol) was greater than its affinity for MAO-A (−7.9 kcal/mol). These findings suggest GC and LG should be considered promising compounds for the treatment of Alzheimer’s disease with multi-targeting activities.

Palmatine: A review of pharmacological properties and pharmacokinetics

The aim of this review is to collect together the results of the numerous studies over the last two decades on the pharmacological properties of palmatine published in scientific databases like Scopus and PubMed, which are scattered across different publications. Palmatine, an isoquinoline alkaloid from the class of protoberberines, is a yellow compound present in the extracts from different representatives of Berberidaceae, Papaveraceae, Ranunculaceae, and Menispermaceae. It has been extensively used in traditional medicine of Asia in the treatment of jaundice, liver-related diseases, hypertension, inflammation, and dysentery. New findings describe its possible applications in the treatment of civilization diseases like central nervous system-related problems. This review intends to let this alkaloid come out from the shade of a more frequently described alkaloid: berberine. The toxicity, pharmacokinetics, and biological activities of this protoberberine alkaloid will be developed in this work.