Comparison of butyrylcholinesterase and acetylcholinesterase

Cholesterol Oxime Olesoxime Assessed as a Potential Ligand of Human Cholinesterases

Olesoxime, a cholesterol derivative with an oxime group, possesses the ability to cross the blood-brain barrier, and has demonstrated excellent safety and tolerability properties in clinical research. These characteristics indicate it may serve as a centrally active ligand of acetylcholinesterase (AChE) and butyrylcholinesterase (BChE), whose disruption of activity with organophosphate compounds (OP) leads to uncontrolled excitation and potentially life-threatening symptoms. To evaluate olesoxime as a binding ligand and reactivator of human AChE and BChE, we conducted in vitro kinetic studies with the active metabolite of insecticide parathion, paraoxon, and the warfare nerve agents sarin, cyclosarin, tabun, and VX. Our results showed that both enzymes possessed a binding affinity for olesoxime in the mid-micromolar range, higher than the antidotes in use (i.e., 2-PAM, HI-6, etc.). While olesoxime showed a weak ability to reactivate AChE, cyclosarin-inhibited BChE was reactivated with an overall reactivation rate constant comparable to that of standard oxime HI-6. Moreover, in combination with the oxime 2-PAM, the reactivation maximum increased by 10-30% for cyclosarin- and sarin-inhibited BChE. Molecular modeling revealed productive interactions between olesoxime and BChE, highlighting olesoxime as a potentially BChE-targeted therapy. Moreover, it might be added to OP poisoning treatment to increase the efficacy of BChE reactivation, and its cholesterol scaffold could provide a basis for the development of novel oxime antidotes.

Experimental and pharmacoinformatic approaches unveil the neuropharmacological and analgesic potential of chloroform fraction of Roktoshirinchi (Achyranthes ferruginea Roxb.)

ETHNOPHARMACOLOGICAL RELEVANCE

Achyranthes ferruginea (A. ferruginea) Roxb. is a common plant used in traditional medicine in Asia and Africa. It has a variety of local names, including "Gulmanci" in Nigeria, "Dangar" in Pakistan, "Thola" in Ethiopia, and "Roktoshirinchi" in Bangladesh. It is edible and has several ethnomedical uses for a wide range of illnesses, including hysteria, dropsy, constipation, piles, boils, asthma, and shigellosis. However, the neuropharmacological and analgesic potential of A. ferruginea remains uninvestigated.

AIM OF THE STUDY

To assess the neuropharmacological and analgesic potential of A. ferruginea through a multifaceted approach encompassing both experimental and computational models.

MATERIALS AND METHODS

Methanol was used to extract the leaves of A. ferruginea. It was then fractionated with low to high polar solvents (n-hexane, chloroform, ethyl acetate, and water) to get different fractions, including chloroform fraction (CLF). The study selected CLF at different doses and conducted advanced chemical element and proximate analyses, as well as phytochemical profiling using GC-MS. Toxicological studies were done at 300 μg per rat per day for 14 days. Cholinesterase inhibitory potential was checked using an in-vitro colorimetric assay. Acetic acid-induced writhing (AAWT) and formalin-induced licking tests (FILT) were used to assess anti-nociceptive effects. The forced swim test (FST), tail suspension test (TST), elevated plus maze (EPM), hole board test (HBT), and light and dark box test (LDB) were among the behavioral tests used to assess depression and anxiolytic activity. Network pharmacology-based analysis was performed on selected compounds using the search tool for interacting chemicals-5 (STITCH 5), Swiss target prediction tool, and search tool for the retrieval of interacting genes and proteins (STRING) database to link their role with genes involved in neurological disorders through gene ontology and reactome analysis.

RESULTS

Qualitative chemical element analysis revealed the presence of 15 elements, including Na, K, Ca, Mg, P, and Zn. The moisture content, ash value, and organic matter were found to be 11.12, 11.03, and 88.97%, respectively. GC-MS data revealed that the CLF possesses 25 phytoconstituents. Toxicological studies suggested the CLF has no effects on normal growth, hematological and biochemical parameters, or cellular organs after 14 days at 300 μg per rat. The CLF markedly reduced the activity of both acetylcholinesterase and butyrylcholinesterase (IC50: 56.22 and 13.22 μg/mL, respectively). Promising dose-dependent analgesic activity (p < 0.05) was observed in chemically-induced pain models. The TST and FST showed a dose-dependent substantial reduction in immobility time due to the CLF. Treatment with CLF notably increased the number of open arm entries and time spent in the EPM test at doses of 200 and 400 mg/kg b.w. The CLF showed significant anxiolytic activity at 200 mg/kg b.w. in the HBT test, whereas a similar activity was observed at 400 mg/kg b.w. in the EPM test. A notable increase in the amount of time spent in the light compartment was observed in the LDB test by mice treated with CLF, suggesting an anxiolytic effect. A network pharmacology study demonstrated the relationship between the phytochemicals and a number of targets, such as PPARA, PPARG, CHRM1, and HTR2, which are connected to the shown bioactivities.

CONCLUSIONS

This study demonstrated the safety of A. ferruginea and its efficacy in attenuating cholinesterase inhibitory activity, central and peripheral pain, anxiety, and depression, warranting further exploration of its therapeutic potential.

Basal forebrain cholinergic systems as circuits through which traumatic stress disrupts emotional memory regulation

Contextual and spatial systems facilitate changes in emotional memory regulation brought on by traumatic stress. Cholinergic basal forebrain (chBF) neurons provide input to contextual/spatial systems and although chBF neurons are important for emotional memory, it is unknown how they contribute to the traumatic stress effects on emotional memory. Clusters of chBF neurons that project to the prefrontal cortex (PFC) modulate fear conditioned suppression and passive avoidance, while clusters of chBF neurons that project to the hippocampus (Hipp) and PFC (i.e. cholinergic medial septum and diagonal bands of Broca (chMS/DBB neurons) are critical for fear extinction. Interestingly, neither Hipp nor PFC projecting chMS/DBB neurons are critical for fear extinction. The retrosplenial cortex (RSC) is a contextual/spatial memory system that receives input from chMS/DBB neurons, but whether this chMS/DBB-RSC circuit facilitates traumatic stress effects on emotional memory remain unexplored. Traumatic stress leads to neuroinflammation and the buildup of reactive oxygen species. These two molecular processes may converge to disrupt chBF circuits enhancing the impact of traumatic stress on emotional memory.

Bioactive cholinesterase inhibitions of clerodanes from the flowers of Croton krabas and molecular docking studies

The first investigation of the phytochemical profile of the flowers of Croton krabas led to the isolation of two new clerodane diterpenes, 6S-crotocaudin (1) and crotocaudin B (2), together with two known clerodanes, 6S-crotoeurin C (3) and isoteucvin (4). The structures and absolute configurations of isolated clerodanes were elucidated by extensive analysis of NMR spectroscopic data, mass spectrometry and ECD calculations. Compounds 1-4 demonstrated significant inhibitory activity towards acetylcholinesterase (AChE). Notably, compound 2 exhibited the strongest AChE inhibition (IC50 1.01 µM). Compounds 3 and 4 showed potent butyrylcholinesterase (BChE) inhibitory activity with IC50 values of 1.09 and 1.12 µM, respectively. The molecular docking results revealed that 2 bound to the catalytic anionic site (CAS) and peripheral anionic site (PAS) of AChE, while 3 occupied in the CAS of BChE.

Machine learning-based virtual screening and molecular modelling studies for identification of butyrylcholinesterase inhibitors as anti-Alzheimer's agent

Butyrylcholinesterase (BChE) is a hydrolase involved in the metabolism and detoxification of specific esters in the blood. It is also implicated in the progression of Alzheimer's disease, a type of dementia. As the disease progresses, the level of BChE tends to increase, opting for a major role as an acetylcholine-degrading enzyme and surpassing the role of acetylcholinesterase. Hence, the development of BChE inhibitors could be beneficial for the latter stages of the disease. In the present study, machine learning (ML) models were developed and employed to identify new BChE inhibitors. Further, the identified molecules were subjected to molecular property filters. The filtered ligands were studied through molecular modelling techniques, viz. molecular docking and molecular dynamics (MD). Support vector machine-based ML models resulted in the identification of 3291 compounds that would have predicted IC50 values less than 200 nM. The docking study showed that compounds ART13069594, ART17350769 and LEG19710163 have mean binding energies of -9.62, -9.26 and -8.93 kcal/mol, respectively. The MD study displayed that all the selected ligands showed stable complexes with BChE. The trajectories of all the ligands were stable similar to the standard BChE inhibitors.Communicated by Ramaswamy H. Sarma.

New Multitarget Rivastigmine-Indole Hybrids as Potential Drug Candidates for Alzheimer's Disease

Alzheimer's disease (AD) is the most common form of dementia with no cure so far, probably due to the complexity of this multifactorial disease with diverse processes associated with its origin and progress. Several neuropathological hallmarks have been identified that encourage the search for new multitarget drugs. Therefore, following a multitarget approach, nine rivastigmine-indole (RIV-IND) hybrids (5a1-3, 5b1-3, 5c1-3) were designed, synthesized and evaluated for their multiple biological properties and free radical scavenging activity, as potential multitarget anti-AD drugs. The molecular docking studies of these hybrids on the active center of acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) suggest their capacity to act as dual enzyme inhibitors with probable greater disease-modifying impact relative to AChE-selective FDA-approved drugs. Compounds 5a3 (IC50 = 10.9 µM) and 5c3 (IC50 = 26.8 µM) revealed higher AChE inhibition than the parent RIV drug. Radical scavenging assays demonstrated that all the hybrids containing a hydroxyl substituent in the IND moiety (5a2-3, 5b2-3, 5c2-3) have good antioxidant activity (EC50 7.8-20.7 µM). The most effective inhibitors of Aβ42 self-aggregation are 5a3, 5b3 and 5c3 (47.8-55.5%), and compounds 5b2 and 5c2 can prevent the toxicity induced by Aβ1-42 to cells. The in silico evaluation of the drug-likeness of the hybrids also showed that all the compounds seem to have potential oral availability. Overall, within this class of RIV-IND hybrids, 5a3 and 5c3 appear as lead compounds for anti-AD drug candidates, deserving further investigation.

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

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

Optical imaging probes for selective detection of butyrylcholinesterase

Butyrylcholinesterase (BChE), a member of the human serine hydrolase family, is an essential enzyme for cholinergic neurotransmission as it catalyzes the hydrolysis of acetylcholine. It also plays central roles in apoptosis, lipid metabolism, and xenobiotic detoxification. On the other side, abnormal levels of BChE are directly associated with the formation of pathogenic states such as neurodegenerative diseases, psychiatric and cardiovascular disorders, liver damage, diabetes, and cancer. Thus, selective and sensitive detection of BChE level in living organisms is highly crucial and is of great importance to further understand the roles of BChE in both physiological and pathological processes. However, it is a very complicated task due to the potential interference of acetylcholinesterase (AChE), the other human cholinesterase, as these two enzymes share a very similar substrate scope. To this end, optical imaging probes have attracted immense attention in recent years as they have modular structures, which can be tuned precisely to satisfy high selectivity toward BChE, and at the same time they offer real time and nondestructive imaging opportunities with a high spatial and temporal resolution. Here, we summarize BChE selective imaging probes by discussing the critical milestones achieved during the development process of these molecular sensors over the years. We put a special emphasis on design principles and biological applications of highly promising new generation activity-based probes. We also give a comprehensive outlook for the future of BChE-responsive probes and highlight the ongoing challenges. This collection marks the first review article on BChE-responsive imaging agents.

Design, synthesis, biological evaluation and molecular docking of cyclic biguanidine compounds as cholinesterase inhibitors

A series of cyclic biguanidine derivatives (E01-E16) was designed, synthesized, characterized by FTIR, NMR, elemental analysis and evaluated as cholinesterase [acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE)] inhibitory effects for the treatment of Alzheimer's disease (AD). The cyclic biguanidine derivatives (E01-E16) were obtained as hydrochloride salt from one-pot reaction of 2-cyanoguanidine, p-substitute aniline derivatives and cyclohexanone/4-ethylcyclohexanone in the acidic medium. The crystal structures of compounds E13 and E16 were determined by XRD studies. The in vitro acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) inhibitory assessment of the compounds revealed that compounds showed considerable inhibitory activity. The substitute groups on the phenyl rings have an impact on the inhibitory activity of the compounds. Compound E08, containing an ester group on the phenyl ring, showed the highest inhibitory activity against BuChE (IC50: 97.97 ± 0.13 µM) compared to other compounds. According to the docking result, compound E08 exhibited higher binding affinity (-10.17 kcal/mol) against BuChE than the standard drug tacrine (-7.02 kcal/mol). Compound E08 was orientated towards the active site of the enzyme BuChE.Communicated by Ramaswamy H. Sarma.

Butyrylcholinesterase and lipid metabolism: Possible dual role in metabolic disorders

Butyrylcholinesterase (BChE), an enzyme primarily found in the liver, plasma, and brain, has been recognized for its role in the hydrolysis of choline esters. Recent studies have shed light on its involvement in lipid metabolism, revealing its potential as a crucial player in maintaining lipid homeostasis. However, the interactions between external factors and BChE activity in lipid metabolic pathways remain a complex subject of study. This review summarizes the current knowledge regarding BChE activity and lipid metabolism and seeks to clarify the nature of this relationship as causal or consequential. Evidence supports the role of BChE in energy homeostasis disruption, such as obesity and related metabolic disorders, where it exhibits lipolytic activity and mediates fatty acid use and storage. The unexpected functions of BChE in lipoprotein synthesis and the impact of polymorphic variants of the BCHE gene suggest a central role in lipid metabolism; however, further investigation is needed to confirm and describe these functions, especially considering the metabolic context. Furthermore, exploring therapeutic interventions in lipid metabolism disorders contributes to elucidating their implications on BChE activity, but attention to the metabolic status and genotypes as possible factors in this interaction is needed. In summary, further research in this field holds promise for improving our understanding of the complex interplay between BChE and lipid metabolism, and its potential clinical applications. However, the available data corroborate the dual role of BChE activity, both as a critical responsive element to metabolic challenges and as a predisposition factor to metabolic diseases.

Chemical Characterization of Different Extracts from Artemisia annua and Their Antioxidant, Enzyme Inhibitory and Anti-Inflammatory Properties

Artemisia annua L. (Asteraceae Family) is an important plant in Asia that has been used for treating different diseases, including fever due to malaria, wounds, tubercolisis, scabues, pain, convulsions, diabetes, and inflammation. In this study we aimed to evaluate the effects of different polarity extracts (hexane, dichloromethane, ethyl acetate, ethanol, ethanol/water (70 %) and water) from A. annua against the burden of inflammation and oxidative stress occurring in colon tissue exposed to LPS. In parallel, chemical composition, antiradical, and enzyme inhibition effects against α-amylase, α-glucosidase, tyrosinase, and cholinesterases were evaluated. The water extract contained the highest content of the total phenolic with 34.59 mg gallic acid equivalent (GAE)/g extract, while the hexane had the highest content of the total flavonoid (20.06 mg rutin equivalent (RE)/g extract). In antioxidant assays, the polar extracts (ethanol, ethanol/water and water) exhibited stronger radical scavenging and reducing power abilities when compared to non-polar extracts. The hexane extract showed the best AChE, tyrosinase and glucosidase inhibitory effects. All extracts revealed effective anti-inflammatory agents, as demonstrated by the blunting effects on COX-2 and TNFα gene expression. These effects seemed to be not related to the only phenolic content. However, it is worthy of interest to highlight how the higher potency against LPS-induced gene expression was shown by the water extract ; thus suggesting a potential phytotherapy application in the management of clinical symptoms related to inflammatory colon diseases, although future in vivo studies are needed to confirm such in vitro and ex vivo observations.

Non-Neuronal Acetylcholinesterase Activity Shows Limited Utility for Early Detection of Sepsis

(1) Background: Sepsis is a severe systemic inflammatory condition characterized by rapid clinical deterioration and organ dysfunction. The cholinergic system has been implicated in modulating the inflammatory response. Acetylcholinesterase (AChE), an enzyme primarily responsible for the hydrolysis of acetylcholine, has been proposed as a potential early indicator of sepsis onset. However, the exact role of non-neuronal AChE activity in sepsis and its correlation with disease severity and patient outcomes remain unclear. This study aimed to investigate the involvement of AChE activity in sepsis and evaluate its association with disease severity and clinical outcomes. (2) Methods: A prospective study included 43 septic patients. AChE activity was measured at sepsis detection, as well as 7 and 28 days later. Inflammatory biomarkers, disease severity scores, and patient outcomes were evaluated. (3) Results: AChE activity remained stable for 7 days and decreased at 28 days. However, there was no correlation between initial AChE activity and inflammatory biomarkers, disease severity scores, ICU stay, or hospital stay. (4) Conclusions: Non-neuronal AChE activity may not reliably indicate early sepsis or predict disease severity.

Real-time visualization of butyrylcholinesterase activity using a highly selective and sensitive chemiluminescent probe

Butyrylcholinesterase (BChE), one of the critical human cholinesterases, plays crucial roles in numerous physiological and pathological processes. Accordingly, it is a striking and at the same time challenging target for bioimaging studies. Herein, we developed the first ever example of a 1,2-dixoetane-based chemiluminescent probe (BCC) for monitoring BChE activity in native biological contexts such as living cells and animals. BCC was initially shown to exhibit a highly selective and sensitive turn-on response in its luminescence signal upon reacting with BChE in aqueous solutions. Later, BCC was utilized to image endogenous BChE activity in normal and cancer cell lines. It was also shown through inhibition experiments that BChE can detect fluctuations of BChE levels successfully. In vivo imaging ability of BCC was demonstrated in healthy and tumor-bearing mice models. BCC enabled us to visualize the BChE activity in different regions of the body. Furthermore, it was successfully employed to monitor tumors derived from neuroblastoma cells with a very high signal to noise ratio. Thus, BCC appears as a highly promising chemiluminescent probe, which can be used to further understand the contribution of BChE to regular cellular processes and the formation of diseased states.

Non-neuronal cholinergic system delays cardiac remodelling in type 1 diabetes

Aims

Type 1 diabetes mellitus (T1DM) is associated with increased risk of cardiovascular disease (CVD) and mortality. The underlying mechanisms for T1DM-induced heart disease still remains unclear. In this study, we aimed to investigate the effects of cardiac non-neuronal cholinergic system (cNNCS) activation on T1DM-induced cardiac remodelling.

Methods

T1DM was induced in C57Bl6 mice using low-dose streptozotocin. Western blot analysis was used to measure the expression of cNNCS components at different time points (4, 8, 12, and 16 weeks after T1DM induction). To assess the potential benefits of cNNCS activation, T1DM was induced in mice with cardiomyocyte-specific overexpression of choline acetyltransferase (ChAT), the enzyme required for acetylcholine (Ac) synthesis. We evaluated the effects of ChAT overexpression on cNNCS components, vascular and cardiac remodelling, and cardiac function.

Key findings

Western blot analysis revealed dysregulation of cNNCS components in hearts of T1DM mice. Intracardiac ACh levels were also reduced in T1DM. Activation of ChAT significantly increased intracardiac ACh levels and prevented diabetes-induced dysregulation of cNNCS components. This was associated with preserved microvessel density, reduced apoptosis and fibrosis, and improved cardiac function.

Significance

Our study suggests that cNNCS dysregulation may contribute to T1DM-induced cardiac remodelling, and that increasing ACh levels may be a potential therapeutic strategy to prevent or delay T1DM-induced heart disease.

Selected herbicides screened for toxicity and analysed as inhibitors of both cholinesterases

Sets of 346 herbicides in use and 163 outdated no longer in use were collected from open access online sources and compared in silico with cholinesterases inhibitors (ChI) and drugs in terms of physicochemical profile and estimated toxic effects on human health. The screening revealed at least one potential adverse consequence for each herbicide class assigned according to their mode of action on weeds. The classes with most toxic warnings were K1, K3/N, F1 and E. The selection of 11 commercial herbicides for in vitro biological tests on human acetylcholinesterase (AChE) and butyrylcholinesterase (BChE), the enzymes involved in neurotoxicity and detoxification of various xenobiotics, respectively, was based mainly on the structural similarity with inhibitors of cholinesterases. Organophosphate anilofos and oxyacetanilide flufenacet were the most potent inhibitors of AChE (25 μM) and BChE (6.4 μM), respectively. Glyphosate, oxadiazon, tembotrione and terbuthylazine were poor inhibitors with an estimated IC₅₀ above 100 μM, while for glyphosate the IC₅₀ was above 1 mM. Generally, all of the selected herbicides inhibited with a slight preference towards BChE. Cytotoxicity assays showed that anilofos, bensulide, butamifos, piperophos and oxadiazon were cytotoxic for hepatocytes (HepG2) and neuroblastoma cell line (SH-SY5Y). Time-independent cytotoxicity accompanied with induction of reactive oxygen species indicated rapid cell death in few hours. Our results based on in silico and in vitro analyses give insight into the potential toxic outcome of herbicides in use and can be applied in the design of new molecules with a less hazardous impact on humans and the environment.

New Thienobenzo/Naphtho-Triazoles as Butyrylcholinesterase Inhibitors: Design, Synthesis and Computational Study

This study aims to test the inhibition potency of new thienobenzo/naphtho-triazoles toward cholinesterases, evaluate their inhibition selectivity, and interpret the obtained results by molecular modeling. The synthesis of 19 new thienobenzo/naphtho-triazoles by two different approaches resulted in a large group of molecules with different functionalities in the structure. As predicted, most prepared molecules show better inhibition of the enzyme butyrylcholinesterase (BChE), considering that the new molecules were designed according to the previous results. Interestingly, the binding affinity of BChE for even seven new compounds (1, 3, 4, 5, 6, 9, and 13) was similar to that reported for common cholinesterase inhibitors. According to computational study, the active thienobenzo- and naphtho-triazoles are accommodated by cholinesterases through H-bonds involving one of the triazole's nitrogens, π-π stacking between the aromatic moieties of the ligand and aromatic residues of the active sites of cholinesterases, as well as π-alkyl interactions. For the future design of cholinesterase inhibitors and search for therapeutics for neurological disorders, compounds with a thienobenzo/naphtho-triazole skeleton should be considered.

Synthesis, in vitro biological screening and docking study of benzo[d]oxazole bis Schiff base derivatives as a potent anti-Alzheimer agent

We have synthesized benzo[d]oxazole derivatives (1-21) through a multistep reaction. Alteration in the structure of derivatives was brought in the last step via using various substituted aromatic aldehydes. In search of an anti-Alzheimer agent, all derivatives were evaluated against acetylcholinesterase and butyrylcholinesterase enzyme under positive control of standard drug donepezil (IC₅₀ = 0.016 ± 0.12 and 4.5 ± 0.11 µM) respectively. In case of acetylcholinesterase enzyme inhibition, derivatives 8, 9 and 18 (IC₅₀ = 0.50 ± 0.01, 0.90 ± 0.05 and 0.3 ± 0.05 µM) showed very promising inhibitory potentials. While in case of butyrylcholinesterase enzyme inhibition, most of the derivatives like 6, 8, 9, 13, 15, 18 and 19 (IC₅₀ = 2.70 ± 0.10, 2.60 ± 0.10, 2.20 ± 0.10, 4.25 ± 0.10, 3.30 ± 0.10, 0.96 ± 0.05 and 3.20 ± 0.10 µM) displayed better inhibitory potential than donepezil. Moreover, derivative 18 is the most potent one among the series in both inhibitions. The binding interaction of derivatives with the active gorge of the enzyme was confirmed via a docking study. Furthermore, the binding interaction between derivatives and the active site of enzymes was correlated through the SAR study. Structures of all derivatives were confirmed through spectroscopic techniques such as ¹H-NMR, ¹³C-NMR and HREI-MS, respectively.Communicated by Ramaswamy H. Sarma.

Lycopodiastrum casuarinoides: An overview of their phytochemicals, biological activities, structure-activity relationship, biosynthetic pathway and 13C NMR data

Huperzine A, a lycodine-type alkaloid, exhibits potent inhibitory activity against acetylcholinesterase (AChE) and has been utilized to treat neurodegenerative diseases' symptoms. Lycopodiastrum casuarinoides, a member of the family Lycopodiaceae, is renowned for its lycodine-type alkaloids. Some of these alkaloids show various pharmacological benefits, such as anti-cholinesterase, neuroprotective, and cytotoxic effects. To date, 113 chemical compounds, including seventy-four lycodine-type alkaloids, ten terpenoids, eleven aliphatics, and eighteen other compounds, have been isolated from this plant. In this review, we have discussed phytochemicals and biological activities of the reported compounds of L. casuarinoides. Moreover, structure-activity relationship (SAR), plausible biosynthetic pathways, and ¹³C nuclear magnetic resonance spectroscopy (¹³C NMR) data of the lycodine-type alkaloids are also summarized.

Response of Oreochromis niloticus (Teleostei: Cichlidae) exposed to a guanitoxin-producing cyanobacterial strain using multiple biomarkers

Changes in environmental conditions in aquatic ecosystems caused by anthropic actions can modify the composition of primary producers, promoting the excessive proliferation of cyanobacteria. These organisms can form cyanobacterial blooms, which directly affect aquatic life. The present study investigated the mutagenicity of the cyanobacterium Sphaerospermopsis torques-reginae (strain ITEP-024), guanitoxin-producing (natural organophosphate), and sublethal effects on fish in relevant environment concentrations. For this, the Ames test (Salmonella/microsome) was performed as a mutagenic assay for extracts of the ITEP-024 strain. Specimens of Oreochromis niloticus (Teleostei: Cichlidae) were subjected to acute 96 h exposure to different concentrations of aqueous extract of the strain: C = control group; T1 = 31.25 mg/L; T2 = 62.5 mg/L; T3 = 125 mg/L; and T4 = 250 mg/L. Genotoxic, biochemical, osmoregulatory, and physiologic biomarkers were analyzed. Our results showed that the cyanobacterium had a weak mutagenic response for the TA102 strain of Salmonella with and without metabolic activation by S9. Strains TA98 and TA100 were not affected. Fish from treatments T3 and T4 showed changes in oxidative stress (CAT, SOD, and GST enzymes), inhibition of the enzyme acetylcholinesterase activity, micronucleus formation, and osmoregulatory disorders. No guanitoxin accumulation was detected in the different tissues of O. niloticus by LC-MS/MS. Our results showed unprecedented mutagenicity data of the guanitoxin-producing cyanobacteria by the Ames test and biochemical, osmoregulatory, and genotoxic disorders in fish, providing efficient aquatic contamination biomarkers. Despite the great concern related to the presence of guanitoxin in blooms in freshwater ecosystems, its concentration is not yet regulated, and thus there is no monitoring agenda in current legislation.

Inhibitory potential of nitrogen, oxygen and sulfur containing heterocyclic scaffolds against acetylcholinesterase and butyrylcholinesterase

Heterocycles are the key structures in organic chemistry owing to their immense applications in the biological, chemical, and pharmaceutical fields. Heterocyclic compounds perform various noteworthy functions in nature, medication, innovation etc. Most frequently, pure nitrogen heterocycles or various positional combinations of nitrogen, oxygen, and sulfur atoms in five or six-membered rings can be found. Inhibition of acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) enzymes is a popular strategy for the management of numerous mental diseases. In this context, cholinesterase inhibitors are utilized to relieve the symptoms of neurological illnesses like dementia and Alzheimer's disease (AD). The present review focuses on various heterocyclic scaffolds and their role in designing and developing new potential AChE and BChE inhibitors to treat AD. Moreover, a detailed structure-activity relationship (SAR) has been established for the future discovery of novel drugs for the treatment of AD. Most of the heterocyclic motifs have been used in the design of new potent cholinesterase inhibitors. In this regard, this review is an endeavor to summarize the biological and chemical studies over the past decade (2010-2022) describing the pursuit of new N, O and S containing heterocycles which can offer a rich supply of promising AChE and BChE inhibitory activities.

Novel Rivastigmine Derivatives as Promising Multi-Target Compounds for Potential Treatment of Alzheimer’s Disease

Alzheimer’s disease (AD) is the most serious and prevalent neurodegenerative disorder still without cure. Since its aetiology is diverse, recent research on anti-AD drugs has been focused on multi-target compounds. In this work, seven novel hybrids (RIV–BIM) conjugating the active moiety of the drug rivastigmine (RIV) with 2 isomeric hydroxyphenylbenzimidazole (BIM) units were developed and studied. While RIV assures the inhibition of cholinesterases, BIM provides further appropriate properties, such as inhibition of amyloid β-peptide (Aβ) aggregation, antioxidation and metal chelation. The evaluated biological properties of these hybrids included antioxidant activity; inhibition of acetylcholinesterase (AChE), butyrylcholinesterase (BChE) and Aβ₄₂ aggregation; as well as promotion of cell viability and neuroprotection. All the compounds are better inhibitors of AChE than rivastigmine (IC₅₀ = 32.1 µM), but compounds of series 5 are better inhibitors of BChE (IC₅₀ = 0.9−1.7 µM) than those of series 4. Series 5 also showed good capacity to inhibit self- (42.1−58.7%) and Cu(II)-induced (40.3−60.8%) Aβ aggregation and also to narrow (22.4−42.6%) amyloid fibrils, the relevant compounds being 5b and 5d. Some of these compounds can also prevent the toxicity induced in SH-SY5Y cells by Aβ₄₂ and oxidative stress. Therefore, RIV–BIM hybrids seem to be potential drug candidates for AD with multi-target abilities.

Enhancement of Cholinesterase Inhibition of Alpinia galanga (L.) Willd. Essential Oil by Microemulsions

This study aimed to investigate the chemical composition and reveal the selective inhibitory activity of Alpinia galanga (L.) Willd. essential oil (AGO) on acetylcholinesterase (AChE) compared to butyrylcholinesterase (BChE). The chemical composition of AGO was investigated by means of gas chromatography–mass spectrometry. Ellman’s method was used to determine the inhibitory activities against AChE and BChE. Microemulsion systems with desirable anticholinesterase effects were developed. Methyl cinnamate and 1,8-cineole were reported as the major component of AGO. The IC₅₀ values of A. galanga oil against AChE and BChE were 24.6 ± 9.6 and 825.4 ± 340.1 µg/mL, respectively. The superior selectivity of AGO on AChE (34.8 ± 8.9) compared to galantamine hydrobromide (6.4 ± 1.5) suggested AGO to be an effective ingredient with fewer side effects for Alzheimer’s treatment. Interestingly, the microemulsion of AGO possessed significantly higher anticholinesterase activity than that of native oil alone. Therefore, microemulsion of AGO is a promising alternative approach for the treatment of Alzheimer’s disease.

Computer Aided Drug Design Methodologies with Natural Products in the Drug Research Against Alzheimer's Disease

Natural products are compounds isolated from plants that provide a variety of lead structures for the development of new drugs by the pharmaceutical industry. The interest in these substances increases because of their beneficial effects on human health. Alzheimer's disease (AD) affects occur in about 80% of individuals aged 65 years. AD, the most common cause of dementia in elderly people, is characterized by progressive neurodegenerative alterations, as decrease of cholinergic impulse, increased toxic effects caused by reactive oxygen species and the inflammatory process that the amyloid plaque participates. In silico studies is relevant in the process of drug discovery; through technological advances in the areas of structural characterization of molecules, computational science and molecular biology have contributed to the planning of new drugs used against neurodegenerative diseases. Considering the social impairment caused by an increased incidence of disease and that there is no chemotherapy treatment effective against AD; several compounds are studied. In the researches for effective neuroprotectants as potential treatments for Alzheimer's disease, natural products have been extensively studied in various AD models. This study aims to carry out a literature review with articles that address the in silico studies of natural products aimed at potential drugs against Alzheimer's disease (AD) in the period from 2015 to 2021.

Acetylcholinesterase from the charru mussel Mytella charruana: kinetic characterization, physicochemical properties and potential as in vitro biomarker in environmental monitoring of mollusk extraction areas

Acetylcholinesterase (AChE; EC 3.1.1.7) from aquatic organisms have been used to evaluate the exposure of specimens to pesticides and heavy metals at sublethal levels in environmental samples. AChE of Mytella charruana was extracted to characterize its physicochemical and kinetic properties as well as the effect of organophosphate (dichlorvos, diazinon, chlorpyrifos, methyl-parathion and temephos), carbamates (carbaryl, carbofuran and aldicarb), benzoylureas (diflubenzuron and novaluron), pyrethroid (cypermethrin) and juvenile hormone analog - JHA (pyriproxyfen) and the effect of metal ions: Hg²⁺, Cd²⁺, Pb²⁺, As³⁺, Cu²⁺ and Zn²⁺, in order to evaluate the potential of the enzyme as biomarker. The optimum pH of M. charruana AChE was 8.5 and the maximum activity peak occurred at 48 °C, being highly thermostable maintaining 97.8% of its activity after incubation at 60 °C. The Michaelis-Menten constants (k_m) for the substrates acetylthiocholine and propionylthiocholine were 2.8 ± 1.26 and 4.94 ± 6.9 mmol·L^-1, respectively. The V_max values for the same substrates were 22.6 ± 0.90 and 10.2 ± 4.94 mU·mg^-1, respectively. Specific inhibition results suggest an AChE presenting active site with dimensions between those of AChE and butyrylcholinesterase (BChE). The IC₂₀ values related to the effect of the pesticides on the enzyme showed higher inhibitory power of temephos (0.17 μmol·L^-1), followed by aldicarb (0.19 μmol·L^-1) and diflubenzuron (0.23 μmol·L^-1). Metal ions inhibited M. charruana enzyme in the following order: Hg²⁺ > Pb²⁺ > Cd²⁺ > As³⁺ > Cu²⁺ > Zn²⁺. These data suggest that the enzyme showed potential as in vitro biomarker of the exposure to temephos, mercury, zinc and copper.

Identification of Compounds for Butyrylcholinesterase Inhibition

Butyrylcholinesterase (BChE) is a nonspecific cholinesterase enzyme that hydrolyzes choline-based esters. BChE plays a critical role in maintaining normal cholinergic function like acetylcholinesterase (AChE) through hydrolyzing acetylcholine (ACh). Selective BChE inhibition has been regarded as a viable therapeutic approach in Alzheimer's disease. As of now, a limited number of selective BChE inhibitors are available. To identify BChE inhibitors rapidly and efficiently, we have screened 8998 compounds from several annotated libraries against an enzyme-based BChE inhibition assay in a quantitative high-throughput screening (qHTS) format. From the primary screening, we identified a group of 125 compounds that were further confirmed to inhibit BChE activity, including previously reported BChE inhibitors (e.g., bambuterol and rivastigmine) and potential novel BChE inhibitors (e.g., pancuronium bromide and NNC 756), representing diverse structural classes. These BChE inhibitors were also tested for their selectivity by comparing their IC50 values in BChE and AChE inhibition assays. The binding modes of these compounds were further studied using molecular docking analyses to identify the differences between the interactions of these BChE inhibitors within the active sites of AChE and BChE. Our qHTS approach allowed us to establish a robust and reliable process to screen large compound collections for potential BChE inhibitors.

Fluorimetric method for specific detection of human serum albumin in urine using its pseudoesterase property

Detection of microalbuminuria is an analytical challenge. There are dye-based methods and immunochemical methods. However, these methods are less specific and sensitive respectively. So, people are trying new approaches for microalbuminuria detection. In this context, we have developed a fluorescent spectroscopic method to detect human serum albumin using its pseudoesterase property. Recently, we had discovered that neostigmine does not inhibit Human serum albumin pseudoesterase activity. Using such a phenomenon, we have devised a specific fluorimetric detection method of HSA using 2NA as a substrate for the pseudoesterase activity. The developed method can sense as low as 0.1 μM of HSA in the urine matrix without dye or antibody. We have proposed a scheme of automation of the proposed method.

Strategic approaches to target the enzymes using natural compounds for the management of Alzheimer's disease: A review

Alzheimer's disease (AD) is a chronic neurodegenerative disease. It is clinically characterized by memory loss and intellectual decrease, among other neurological deficits. The etiology of AD is not completely understood but includes amyloid plaques and intracellular helical filaments as well as neurofibrillary tangles with hyperphosphorylated tau protein. AD is also associated with alterations in amyloid processing genes, such as PSEN1 or PSEN2 and APP. The modulation immune system, cholesterol metabolism, and synaptic vesicle endocytosis have all been shown to remediate AD. In this review, enzymes such as AChE, BuChE, β-secretase, γ-secretase, MAO, and RAGE are discussed as potential targets for AD treatment. The aim of this review was to addresses the molecular mechanisms as well as various genetic factors in AD etiology. The use of natural compounds against these targets might be beneficial for the management of AD.

Analysis of Carotenoids in Haloarchaea Species from Atacama Saline Lakes by High Resolution UHPLC-Q-Orbitrap-Mass Spectrometry: Antioxidant Potential and Biological Effect on Cell Viability

Haloarchaea are extreme halophilic microorganisms belonging to the domain Archaea, phylum Euryarchaeota, and are producers of interesting antioxidant carotenoid compounds. In this study, four new strains of Haloarcula sp., isolated from saline lakes of the Atacama Desert, are reported and studied by high-resolution mass spectrometry (UHPLC-Q-Orbitrap-MS/MS) for the first time. In addition, determination of the carotenoid pigment profile from the new strains of Haloarcula sp., plus two strains of Halorubrum tebenquichense, and their antioxidant activity by means of several methods is reported. The effect of biomass on cellular viability in skin cell lines was also evaluated by MTT assay. The cholinesterase inhibition capacity of six haloarchaea (Haloarcula sp. ALT-23; Haloarcula sp. TeSe-41; Haloarcula sp. TeSe-51; Haloarcula sp. Te Se-89 and Halorubrum tebenquichense strains TeSe-85 and Te Se-86) is also reported for the first time. AChE inhibition IC₅₀ was 2.96 ± 0.08 μg/mL and BuChE inhibition IC₅₀ was 2.39 ± 0.09 μg/mL for the most active strain, Halorubrum tebenquichense Te Se-85, respectively, which is more active in BuCHe than that of the standard galantamine. Docking calculation showed that carotenoids can exert their inhibitory activity fitting into the enzyme pocket by their halves, in the presence of cholinesterase dimers.

Modulation of preeclampsia by the cholinergic anti-inflammatory pathway: Therapeutic perspectives

The cholinergic anti-inflammatory pathway (CAP) is vital for the orchestration of the immune and inflammatory responses under normal and challenged conditions. Over the past two decades, peripheral and central circuits of CAP have been shown to be critically involved in dampening the inflammatory reaction in a wide array of inflammatory disorders. Additionally, emerging evidence supports a key role for CAP in the regulation of the female reproductive system during gestation as well as in the advent of serious pregnancy-related inflammatory insults such as preeclampsia (PE). Within this framework, the modulatory action of CAP encompasses the perinatal maternal and fetal adverse consequences that surface due to antenatal PE programming. Albeit, a considerable gap still exists in our knowledge of the precise cellular and molecular underpinnings of PE/CAP interaction, which hampered global efforts in safeguarding effective preventive or therapeutic measures against PE complications. Here, we summarize reports in the literature regarding the roles of peripheral and reflex cholinergic neuroinflammatory pathways of nicotinic acetylcholine receptors (nAChRs) in reprogramming PE complications in mothers and their progenies. The possible contributions of α7-nAChRs, cholinesterases, immune cells, adhesion molecules, angiogenesis, and endothelial dysfunction to the interaction have also been reviewed.

Phytochemical Analysis and Evaluation of Biological Activity of Lawsonia inermis Seeds Related to Alzheimer's Disease

Using Lawsonia inermis L. (henna) seeds has been frequently recommended for the improvement of memory in Iranian Traditional Medicine (ITM). In this respect, different fractions of the plant were prepared and evaluated for their in vitro biological assays related to Alzheimer's disease (AD), including acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) inhibitory activity as well as metal chelating ability and DPPH antioxidant activity. The dichloromethane and ethyl acetate fractions were able to inhibit the BChE selectively with IC₅₀ values of 113.47 and 124.90 μg/mL, respectively, compared with donepezil as the reference drug (IC₅₀ = 1.52 μg/mL). However, all fractions were inactive toward AChE. Phytochemical analysis of the dichloromethane fraction indicated the presence of β-sitosterol (1), 3-O-β-acetyloleanolic acid (2), 3-O-(Z)-coumaroyl oleanolic acid (3), betulinic acid (4), and oleanolic acid (5). The inhibitory activity of isolated compounds was also evaluated toward AChE and BChE. Among them, compounds 2 and 5 showed potent inhibitory activity toward BChE with IC₅₀ values of 77.13 and 72.20 μM, respectively. However, all compounds were inactive toward AChE. Moreover, molecular docking study confirmed desired interactions between those compounds and the BChE active site. The ability of fractions and compounds to chelate biometals (Cu²⁺, Fe²⁺, and Zn²⁺) was also investigated. Finally, DPPH antioxidant assay revealed that the ethyl acetate (IC₅₀ = 3.08 μg/mL) and methanol (IC₅₀ = 3.64 μg/mL) fractions possessed excellent antioxidant activity in comparison to BHA as the positive control (IC₅₀ = 3.79 μg/mL).

In silico, theoretical biointerface analysis and in vitro kinetic analysis of amine compounds interaction with acetylcholinesterase and butyrylcholinesterase

Acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) are considered important target for drug design against Alzheimer's disease. In the present study in silico analysis; theoretical analysis of biointerface between ligand and interacting amino acid residues of proteins; and in vitro analysis of enzyme inhibition kinetics were carried out to delineate the inhibitory property of amine compounds against AChE/BChE. High throughput virtual screening of amine compounds identified three compounds (2-aminoquinoline, 2-aminobenzimidazole and 2-amino-1-methylbenzimidazole) that best interacted with AChE/BChE. Molecular docking analysis revealed the interaction of these compounds in the active site gorge of AChE/BChE, in particular with amino acid residues present in the peripheral anionic site. Molecular dynamics simulation confirmed the stable binding of these compounds with AChE/BChE. Binding energy calculated through MMGBSA method identified the non-covalent interactions (electrostatic and Van der Waals interactions) have contributed to the stable binding of the amine compounds with the AChE/BChE. Biointerface between amine compounds and AChE/BChE were visualized through Hirshfeld surface analysis. The inter-fragment interaction energies for the possible contacts between amine compounds and amino acid residues were carried out for the first time. All the amine compounds showed mixed-type of inhibition with moderate Ki value in in vitro analysis.

Pyridinium-2-carbaldoximes with quinolinium carboxamide moiety are simultaneous reactivators of acetylcholinesterase and butyrylcholinesterase inhibited by nerve agent surrogates

The pyridinium-2-carbaldoximes with quinolinium carboxamide moiety were designed and synthesised as cholinesterase reactivators. The prepared compounds showed intermediate-to-high inhibition of both cholinesterases when compared to standard oximes. Their reactivation ability was evaluated in vitro on human recombinant acetylcholinesterase (hrAChE) and human recombinant butyrylcholinesterase (hrBChE) inhibited by nerve agent surrogates (NIMP, NEMP, and NEDPA) or paraoxon. In the reactivation screening, one compound was able to reactivate hrAChE inhibited by all used organophosphates and two novel compounds were able to reactivate NIMP/NEMP-hrBChE. The reactivation kinetics revealed compound 11 that proved to be excellent reactivator of paraoxon-hrAChE better to obidoxime and showed increased reactivation of NIMP/NEMP-hrBChE, although worse to obidoxime. The molecular interactions of studied reactivators were further identified by in silico calculations. Molecular modelling results revealed the importance of creation of the pre-reactivation complex that could lead to better reactivation of both cholinesterases together with reducing particular interactions for lower intrinsic inhibition by the oxime.

Acetylcholinesterase and human cancers

The enzyme acetylcholinesterase (AChE) is a serine hydrolase whose primary function is to degrade acetylcholine (ACh) and terminate neurotransmission. Apart from its role in synaptic transmission, AChE has several "non-classical" functions in non-neuronal cells. AChE is involved in cellular growth, apoptosis, drug resistance pathways, response to stress signals and inflammation. The observation that the functional activity of AChE is altered in human tumors (relative to adjacent matched normal tissue) has raised several intriguing questions about its role in the pathophysiology of human cancers. Published reports show that AChE is a vital regulator of oncogenic signaling pathways involving proliferation, differentiation, cell-cell adhesion, migration, invasion and metastasis of primary tumors. The objective of this book chapter is to provide a comprehensive overview of the contributions of the AChE-signaling pathway in the growth of progression of human cancers. The AChE isoforms, AChE-T, AChE-R and AChE-S are robustly expressed in human cancer cell lines as well in human tumors (isolated from patients). Traditionally, AChE-modulators have been used in the clinic for treatment of neurodegenerative disorders. Emerging studies reveal that these drugs could be repurposed for the treatment of human cancers. The discovery of potent, selective AChE ligands will provide new knowledge about AChE-regulatory pathways in human cancers and foster the hope of novel therapies for this disease.

1H-1,2,3-triazole grafted tacrine-chalcone conjugates as potential cholinesterase inhibitors with the evaluation of their behavioral tests and oxidative stress in mice brain cells

The present paper explicates the synthesis of 1H-1,2,3-triazole tethered tacrine-chalcone conjugates and evaluation of their AChE and BuChE inhibitory activity. In-vitroAChE inhibition assay revealed three compounds, 9h, 9i, and 11f, being more potent than the standard drug tacrine and further evaluated against butyrylcholinesterase. The present study was extended to investigate the anti-amnestic effect of promising compoundson scopolamine-induced behavioral and neurochemical changes in mice. Inclined plane model and Elevated plus-maze model were performed to assess general limb motor activity and anxiety-like behavior, respectively, in mice pre-treated with scopolamine. Oxidative stress parameters reduced glutathione contents (GSH) and lipid peroxidation products (TBARS) in the brain homogenates as estimated using ex-vivo studies. Furthermore, molecular docking studies were performed for the potent compounds to decipher the mechanism of observed activities.

Highly Potent and Selective Butyrylcholinesterase Inhibitors for Cognitive Improvement and Neuroprotection

Butyrylcholinesterase (BChE) has been considered as a potential therapeutic target for Alzheimer's disease (AD) because of its compensation capacity to hydrolyze acetylcholine (ACh) and its close association with Aβ deposit. Here, we identified S06-1011 (hBChE IC50 = 16 nM) and S06-1031 (hBChE IC50 = 25 nM) as highly effective and selective BChE inhibitors, which were proved to be safe and long-acting. Candidate compounds exhibited neuroprotective effects and the ability to improve cognition in scopolamine- and Aβ1-42 peptide-induced cognitive deficit models. The best candidate S06-1011 increased the level of ghrelin, a substrate of BChE, which can function as improving the mental mood appetite. The weight gain of the S06-1011-treated group remarkably increased. Hence, BChE inhibition not only plays a protective role against dementia but also exerts a great effect on treating and nursing care.

Design, synthesis and evaluation of cholinesterase hybrid inhibitors using a natural steroidal alkaloid as precursor

To date, Alzheimer's disease is the most alarming neurodegenerative disorder worldwide. This illness is multifactorial in nature and cholinesterase inhibitors have been the ones used in clinical treatments. In this context, many of these drugs selectively inhibit the acetylcholinesterase enzyme interacting in both the active site and the peripheric anionic site. Besides, some agents have exhibited extensive benefits being able to co-inhibit butyrylcholinesterase. In this contribution, a strategy previously explored by numerous authors is reported; the synthesis of hybrid cholinesterase inhibitors. This strategy uses a molecule of recognized high inhibitory activity (tacrine) together with a steroidal alkaloid of natural origin using different connectors. The biological assays demonstrated the improvement in the inhibitory activity compared to the alkaloidal precursor, together with the reinforcement of the interactions in multiple sites of the enzymatic cavity. This strategy should be explored and exploited in this area. Docking and molecular dynamic studies were performed to explain enzyme-ligand interactions, assisting a structure-activity relationship analysis.

Ajmalicine and its Analogues Against AChE and BuChE for the Management of Alzheimer's Disease: An In-silico Study

BACKGROUND

Alzheimer's disease (AD) is the most well-known reason for disability in persons aged greater than 65 years worldwide. AD influences the part of the brain that controls cognitive and non-cognitive functions.

OBJECTIVE

The study focuses on the screening of natural compounds for the inhibition of AChE and BuChE using a computational methodology.

METHODS

We performed a docking-based virtual screening utilizing the 3D structure of AChE and BuChE to search for potential inhibitors for AD. In this work, a screened inhibitor Ajmalicine similarity search was carried out against a natural products database (Super Natural II). Lipinski rule of five was carried out and docking studies were performed between ligands and enzyme using 'Autodock4.2'.

RESULTS

Two phytochemical compounds SN00288228 and SN00226692 were predicted for the inhibition of AChE and BuChE, respectively. The docking results revealed Ajmalicine, a prominent natural alkaloid, showing promising inhibitory potential against AChE and BuChE with the binding energy of -9.02 and -8.89 kcal/mole, respectively. However, SN00288228- AChE, and SN00226692-BuChE were found to have binding energy -9.88 and -9.54 kcal/mole, respectively. These selected phytochemical compounds showed better interactions in comparison to Ajmalicine with the target molecule.

CONCLUSION

The current study verifies that SN00288228 and SN00226692 are more capable inhibitors of human AChE and BuChE as compared to Ajmalicine with reference to ΔG values.

Pseudosterase activity-based specific detection of human serum albumin on gel

Human serum albumin (HSA) has pseudoesterase activity. So far on gel specific detection of such property of HSA is never reported. Moreover, protein binding dyes are non-specific for albumin. However, many of such dyes are used for HSA detection. So, dye-based albumin detection on the gel is expected to generate false-positive results for HSA. In this context, we have discovered that Fast Blue BB (FBBB, 0.12%) stains specifically HSA pseudoesterase activity with 2 Naphthyl acetate (2NA) as an ester substrate. Further, neostigmine has not inhibited the pseudoesterase activity associated with HSA. Neostigmine is a known inhibitor of many true esterases like acetylcholinesterase. So, neostigmine addition offers specificity to the method developed for staining of HSA. Additionally, 2NA stains HSA better than bovine serum albumin (BSA). Exploring all these novel findings, we have devised a simple method of HSA detection on the gel, accurately where other esterases are not detected. To the best of our knowledge, our method is the first to detect HSA pseudoesterase activity specifically on gel without getting interfered by any other esterase activity. The method detects HSA better than BSA. We feel that this method will go a long way for the specific detection of HSA on the gel. It is also relevant for understanding the purity of donor human milk matrix and pharmaceutical preparation of HSA. Our method can detect 7 μM of added HSA in human urine. Therefore, our method can be proceeded further for microalbuminuria detection in days to come.

Essential Oils as a Potential Neuroprotective Remedy for Age-Related Neurodegenerative Diseases: A Review

Despite the improvements in life expectancy, neurodegenerative conditions have arguably become the most dreaded maladies of older people. The neuroprotective and anti-ageing potentials of essential oils (EOs) are widely evaluated around the globe. The objective of this review is to analyse the effectiveness of EOs as neuroprotective remedies among the four common age-related neurodegenerative diseases. The literature was extracted from three databases (PubMed, Web of Science and Google Scholar) between the years of 2010 to 2020 using the medical subject heading (MeSH) terms "essential oil", crossed with "Alzheimer's disease (AD)", "Huntington's disease (HD)", "Parkinson's disease (PD)" or "amyotrophic lateral sclerosis (ALS)". Eighty three percent (83%) of the studies were focused on AD, while another 12% focused on PD. No classifiable study was recorded on HD or ALS. EO from Salvia officinalis has been recorded as one of the most effective acetylcholinesterase and butyrylcholinesterase inhibitors. However, only Cinnamomum sp. has been assessed for its effectiveness in both AD and PD. Our review provided useful evidence on EOs as potential neuroprotective remedies for age-related neurodegenerative diseases.

Non-neuronal Role of Acetylcholinesterase in Bone Development and Degeneration

Acetylcholinesterase (AChE), an enzyme catalyzing the degradation of acetylcholine, plays an important suppressive role in the cholinergic regulation by terminating the action of acetylcholine. The expression of acetylcholinesterase and other cholinergic components is not restricted to only brain and nerve tissues but can also be found in non-neuronal tissues like the immune system and bone tissue. Primary identification of these components has been achieved. However, the information about their specific functions and underlying molecular mechanisms in bone remains scattered. Here, the physiological process of bone development, homeostasis, and degeneration are introduced. Next, the cholinergic system and its expression in bone tissue is documented. Among them, special attention goes to AChE, as the structure of this enzyme suggests diverse binding affinities, enabled by a peripheral site and a catalytic site. The peripheral site supports the non-enzymatic function of AChE in non-neuronal systems. Based on recent studies, the non-neuronal roles of acetylcholinesterase, both enzymatically and non-enzymatically, in bone development, homeostasis and degeneration are summarized briefly together with potential mechanisms to support these functions. We conclude that AChE may be a potential therapeutic target for bone diseases like osteoporosis.

Counteracting poisoning with chemical warfare nerve agents

Phosphylation of the pivotal enzyme acetylcholinesterase (AChE) by nerve agents (NAs) leads to irreversible inhibition of the enzyme and accumulation of neurotransmitter acetylcholine, which induces cholinergic crisis, that is, overstimulation of muscarinic and nicotinic membrane receptors in the central and peripheral nervous system. In severe cases, subsequent desensitisation of the receptors results in hypoxia, vasodepression, and respiratory arrest, followed by death. Prompt action is therefore critical to improve the chances of victim's survival and recovery. Standard therapy of NA poisoning generally involves administration of anticholinergic atropine and an oxime reactivator of phosphylated AChE. Anticholinesterase compounds or NA bioscavengers can also be applied to preserve native AChE from inhibition. With this review of 70 years of research we aim to present current and potential approaches to counteracting NA poisoning.

Inhibition of cholinesterases by safranin O: Integration of inhibition kinetics with molecular docking simulations

In the present study, the inhibitory mechanisms and effects of a synthetic phenazine dye, safranin O (SO) on human plasma butyrylcholinesterase (BChE), human erythrocyte acetylcholinesterase (AChE) and recombinant BChE mutants were investigated. Kinetic studies showed the following information: SO leaded to linear competitive inhibition of human plasma BChE with K_i = 0.44 ± 0.085 μM; α = ∞. It acted as a hyperbolic noncompetitive inhibitor of human erythrocyte AChE with K_i = 0.69 ± 0.13; α = 1; β = 0.08 ± 0.02. On the other hand, the inhibitory effects of SO on two BChE mutants, where A328 was modified to either F or Y, revealed differences in terms of inhibitory patterns and K_i values, compared to the obtained results with recombinant wild type BChE. SO was found to act as a linear competitive inhibitor of A328F and A328Y BChE mutants. Compared to recombinant wild type BChE, A328Y and A328F BChE mutants caused a 4- and 10-fold decrease in K_i value for SO, respectively. These findings were supported by molecular modelling studies. In conclusion, SO is a potent inhibitor of human cholinesterases and may be useful in the design and development of new drugs for the treatment of AD.