Identification of Compounds for Butyrylcholinesterase Inhibition

Evaluation of N-alkyl isatins and indoles as acetylcholinesterase and butyrylcholinesterase inhibitors

Two series of N-alkyl isatins and N-alkyl indoles varying in size of the alkyl group were synthesised and evaluated for inhibition of acetylcholinesterase (AChE) and butyrylcholinesterase (BChE). Among the N-alkyl isatins 4a-j, the addition of the N-alkyl group improved inhibition potency towards AChE and BChE compared to isatin. Selectivity towards inhibition of BChE was observed, and the increase in size of the N-alkyl group positively correlated to improved inhibition potency. The most potent inhibitor for BChE was 4i (IC50 = 3.77 µM, 22-fold selectivity for BChE over AChE). N-alkyl indoles 5a-j showed similar inhibition of AChE, the most potent being 5g (IC50 = 35.0 µM), but 5a-j lost activity towards BChE. This suggests an important role of the 3-oxo group on isatin for BChE inhibition, and molecular docking of 4i with human BChE indicates a key hydrogen bond between this group and Ser198 and His438 of the BChE catalytic triad.

Studies on Secondary Metabolites and In vitro and In silico Anticholinesterases Activities of the Sea Urchin Echinometra mathaei Crude Venoms from the Persian Gulf-Bushehr

Background:

Echinoderms are a unique source of amazing secondary metabolites with a wide spectrum of biological activities. Several species of sea urchins contain various toxins and biologically active metabolites. One of the most attractive approaches to treat Alzheimer's disease is searching for effective marine natural products with cholinesterase inhibitory activities.

Objective:

The current study is designed to investigate the in vitro and in silico acetylcholinesterase and butyrylcholinesterase inhibitory activities of the Persian Gulf echinoderm sea urchin Echinometra mathaei venom and related chemical compounds.

Methods:

The experiments for LD50, total protein, protein bands, in vitro cholinesterase inhibitory activities, the identity of secondary metabolites, and the in silico evaluations, respectively, were performed by Spearman-Karber, Lowry, SDS-PAGE, Ellman's spectroscopic, GC-MS, and docking methods.

Results:

The LD50 (IV rat) of the spine, gonad, and coelomic fluid from sea urchin samples were 2.231 ± 0.09, 1.03 ± 0.05, and 1.12 ± 0.13 mg/ml, respectively. The SDS-PAGE and total protein studies showed that at least a portion of the venom is protein in nature. GC-MS analysis of the identified samples revealed 12, 23, and 21 compounds with different chemical types, including alkaloids, terpenes, and steroids, respectively. According to the results, all samples act as significant inhibitors of both enzymes. In silico data for the identified compounds also confirmed the experimental results.

Conclusion:

The alkaloid compound 6H-Indolo[3,2,1-de] [1,5] naphthyridine-6-one,1,2,3a,4,5- hexahydro-8-hydroxy-3-methyl (C7) had the highest affinity for both enzymes. Further research is needed to determine whether C7 could be a therapeutic candidate for Alzheimer's disease.

Umbelliferone and Its Synthetic Derivatives as Suitable Molecules for the Development of Agents with Biological Activities: A Review of Their Pharmacological and Therapeutic Potential

Umbelliferone (UMB), known as 7-hydroxycoumarin, hydrangine, or skimmetine, is a naturally occurring coumarin in the plant kingdom, mainly from the Umbelliferae family that possesses a wide variety of pharmacological properties. In addition, the use of nanoparticles containing umbelliferone may improve anti-inflammatory or anticancer therapy. Also, its derivatives are endowed with great potential for therapeutic applications due to their broad spectrum of biological activities such as anti-inflammatory, antioxidant, neuroprotective, antipsychotic, antiepileptic, antidiabetic, antimicrobial, antiviral, and antiproliferative effects. Moreover, 7-hydroxycoumarin ligands have been implemented to develop 7-hydroxycoumarin-based metal complexes with improved pharmacological activity. Besides therapeutic applications, umbelliferone analogues have been designed as fluorescent probes for the detection of biologically important species, such as enzymes, lysosomes, and endosomes, or for monitoring cell processes and protein functions as well various diseases caused by an excess of hydrogen peroxide. Furthermore, 7-hydroxy-based chemosensors may serve as a highly selective tool for Al3+ and Hg2+ detection in biological systems. This review is devoted to a summary of the research on umbelliferone and its synthetic derivatives in terms of biological and pharmaceutical properties, especially those reported in the literature during the period of 2017-2023. Future potential applications of umbelliferone and its synthetic derivatives are presented.

Enterobacter hormaechei-Driven Novel Biosynthesis of Tin Oxide Nanoparticles and Evaluation of Their Anti-aging, Cytotoxic, and Enzyme Inhibition Potential

Nanotechnology is a research hotspot that has gained considerable interest due to its potential inferences in the bioscience, medical, and engineering disciplines. The present study uses biomass from the Enterobacter hormaechei EAF63 strain to create bio-inspired metallic tin oxide nanoparticles (SnO2 NPs). The biosynthesized NPs were extensively analyzed using UV spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and Fourier transform infrared (FTIR) techniques. The identification of the crystalline phase was confirmed by XRD. The SEM technique elucidated the morphological characteristics and size of SnO2 NPs. SEM investigation revealed that the SnO2 NPs have a size of 10 nm with spherical morphology. The capping of NPs was confirmed by FTIR analysis that revealed the presence of different compounds found in the biomass of the E. hormaechei EAF63 strain. Later, EDX confirmed the elemental composition of NPs. Moreover, the synthesized SnO2 NPs were employed for important applications including anti-aging, anti-Alzheimer's, anti-inflammatory, anti-larvicidal, and antibacterial action against sinusitis pathogens. The highest value was observed for Streptococcus pyogenes (19.75 ± 0.46), followed by Moraxella catarrhalis (17.49 ± 0.82) and Haemophilus influenzae (15.31 ± 0.73), respectively. Among the used concentrations, the highest inhibition of 76.8 ± 0.93 for 15-lipoxygenase (15-LOX) was observed at 400 μg/mL, followed by 67.4 ± 0.91 for cyclooxygenase-1 (COX-1). So, as an outcome, E. hormaechei-mediated SnO2 NPs might be considered as the safe and effective nanoplatforms for multifunctional biological applications in the field of nanomedicine.

Identification of Potent and Selective Acetylcholinesterase/Butyrylcholinesterase Inhibitors by Virtual Screening

Acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) play important roles in human neurodegenerative disorders such as Alzheimer's disease. In this study, machine learning methods were applied to develop quantitative structure-activity relationship models for the prediction of novel AChE and BChE inhibitors based on data from quantitative high-throughput screening assays. The models were used to virtually screen an in-house collection of ∼360K compounds. The optimal models achieved good performance with area under the receiver operating characteristic curve values ranging from 0.83 ± 0.03 to 0.87 ± 0.01 for the prediction of AChE/BChE inhibition activity and selectivity. Experimental validation showed that the best-performing models increased the assay hit rate by several folds. We identified 88 novel AChE and 126 novel BChE inhibitors, 25% (AChE) and 53% (BChE) of which showed potent inhibitory effects (IC50 < 5 μM). In addition, structure-activity relationship analysis of the BChE inhibitors revealed scaffolds for chemistry design and optimization. In conclusion, machine learning models were shown to efficiently identify potent and selective inhibitors against AChE and BChE and novel structural series for further design and development of potential therapeutics against neurodegenerative disorders.

Anti-Cholinesterase and Anti-α-Amylase Activities and Neuroprotective Effects of Carvacrol and p-Cymene and Their Effects on Hydrogen Peroxide Induced Stress in SH-SY5Y Cells

Several researchers have demonstrated the health and pharmacological properties of carvacrol and p-cymene, monoterpenes of aromatic plants. This study investigated these compounds' possible anti-cholinesterase, anti-α-amylase, and neuroprotective effects. We evaluated the anti-acetylcholinesterase and anti-α-amylase activities at different concentrations of the compounds. The maximum non-toxic dose of carvacrol and p-cymene against SH-SY5Y neuroblastoma cells was determined using an MTT assay. The neuroprotective effects of the compounds were evaluated on H₂O₂-induced stress in SH-SY5Y cells, studying the expression of caspase-3 using Western blotting assays. Carvacrol showed inhibitory activities against acetylcholinesterase (IC50 = 3.8 µg/mL) and butyrylcholinesterase (IC₅₀ = 32.7 µg/mL). Instead, the anti-α-amylase activity of carvacrol resulted in an IC₅₀ value of 171.2 μg/mL After a pre-treatment with the maximum non-toxic dose of carvacrol and p-cymene, the expression of caspase-3 was reduced compared to cells treated with H₂O₂ alone. Carvacrol and p-cymene showed in vitro anti-enzymatic properties, and may act as neuroprotective agents against oxidative stress. Further studies are necessary to elucidate their possible use as coadjutants in preventing and treating AD in diabetic patients.

Ultrasound-Assisted Extraction, LC-MS/MS Analysis, Anticholinesterase, and Antioxidant Activities of Valuable Natural Metabolites from Astragalus armatus Willd.: In Silico Molecular Docking and In Vitro Enzymatic Studies

The Astragalus armatus Willd. plant’s phenolic constituent extraction and identification were optimized using the ultrasound-assisted extraction (UAE) method and the LC–MS/MS analysis, respectively. Additionally, cupric reducing antioxidant capacity (CUPRAC), beta carotene, reducing power, DMSO alcalin, silver nanoparticle (SNP)-based method, phenanthroline, and hydroxyl radical tests were utilized to assess the extract’s antioxidant capacity, while the neuroprotective effect was examined in vitro against acetylcholinesterase enzyme. This study accurately estimated the chemical bonding between the identified phenolic molecules derived from LC–MS/MS and the AChE. The extract was found to contain sixteen phenolic substances, and rosmarinic, protocatechuic, and chlorogenic acids, as well as 4-hydroxybenzoic, hyperoside, and hesperidin, were the most abundant substances in the extract. In all antioxidant experiments, the plant extract demonstrated strong antioxidant activity and a significant inhibitory impact against AChE (40.25 ± 1.41 μg/mL). According to molecular docking affinity to the enzyme AChE, the top-five molecules were found to be luteolin, quercetin, naringenin, rosmarinic acid, and kaempferol. Furthermore, these tested polyphenols satisfy the essential requirements for drug-like characteristics and Lipinski’s rule of five. These results highlight the significance of the A. armatus plant in cosmetics, as food additives, and in the pharmaceutical industry due to its rosmarinic and chlorogenic acid content.

Design, Synthesis and Biological Evaluation of Biscarbamates as Potential Selective Butyrylcholinesterase Inhibitors for the Treatment of Alzheimer's Disease

As butyrylcholinesterase (BChE) plays a role in the progression of symptoms and pathophysiology of Alzheimer's disease (AD), selective inhibition of BChE over acetylcholinesterase (AChE) can represent a promising pathway in treating AD. The carbamate group was chosen as a pharmacophore because the carbamates currently or previously in use for the treatment of AD displayed significant positive effects on cognitive symptoms. Eighteen biscarbamates with different substituents at the carbamoyl and hydroxyaminoethyl chain were synthesized, and their inhibitory potential toward both cholinesterases and inhibition selectivity were determined. The ability of carbamates to cross the blood-brain barrier (BBB) by passive transport, their cytotoxic profile and their ability to chelate biometals were also evaluated. All biscarbamates displayed a time-dependent inhibition with inhibition rate constants within 10^-3-10^-6 M^-1 min^-1 range for both cholinesterases, with generally higher preference to BChE. For two biscarbamates, it was determined that they should be able to pass the BBB by passive transport, while for five biscarbamates, this ability was slightly limited. Fourteen biscarbamates did not exhibit a cytotoxic effect toward liver, kidney and neuronal cells. In conclusion, considering their high BChE selectivity, non-toxicity, ability to chelate biometals and pass the BBB, compounds 2 and 16 were pointed out as the most promising compounds for the treatment of middle and late stages of AD.

Synthesis of 4-substituted benzyl-2-triazole-linked-tryptamine-paeonol derivatives and evaluation of their selective inhibitions against butyrylcholinesterase and monoamine oxidase-B

Cholinesterase (ChE) and monoamine oxidase (MAO) inhibitors are being used and developed to treat Alzheimer's disease (AD), a major type of dementia patients. Fifteen 4-substituted benzyl-2-triazole-linked-tryptamine-paeonol derivatives were synthesized and evaluated for their inhibitory activities against acetylcholinesterase (AChE), butyrylcholinesterase (BChE), monoamine oxidase-A (MAO-A), and B (MAO-B). Compound 896 was the most potent BChE inhibitor (IC₅₀ = 0.13 μM) with the selectivity index (SI) value of >769.23 for BChE over AChE. Compound 897 was the most potent selective MAO-B inhibitor (IC₅₀ = 0.73 μM; SI = 20.45 for MAO-B over MAO-A). The meta-CF₃ substituent of 896 increased BChE inhibitory activity and the para-CF₃ substituent of 897 increased MAO-B inhibitory activity. Compound 896 was a reversible noncompetitive BChE inhibitor (K_i = 0.171 μM) and 897 was a reversible competitive MAO-B inhibitor (K_i = 0.237 μM). Compound 896 had a lower binding energy (-13.75 kcal/mol) to BChE than 897 (-11.29 kcal/mol), and 897 had a lower binding energy to MAO-B (-11.31 kcal/mol) than that to MAO-A (-6.72 kcal/mol). Little cytotoxicity was observed for 896 and 897 to normal cells (MDCK) and human neuroblastoma cells (SH-SY5Y). This study suggested that 896 and 897 are therapeutic candidates for various neurodegenerative disorders such as AD.

Use of Tox21 Screening Data to Evaluate the COVID-19 Drug Candidates for Their Potential Toxic Effects and Related Pathways

Currently, various potential therapeutic agents for coronavirus disease-2019 (COVID-19), a global pandemic caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), are being investigated worldwide mainly through the drug repurposing approach. Several anti-viral, anti-bacterial, anti-malarial, and anti-inflammatory drugs were employed in randomized trials and observational studies for developing new therapeutics for COVID-19. Although an increasing number of repurposed drugs have shown anti-SARS-CoV-2 activities in vitro, so far only remdesivir has been approved by the US FDA to treat COVID-19, and several other drugs approved for Emergency Use Authorization, including sotrovimab, tocilizumab, baricitinib, paxlovid, molnupiravir, and other potential strategies to develop safe and effective therapeutics for SARS-CoV-2 infection are still underway. Many drugs employed as anti-viral may exert unwanted side effects (i.e., toxicity) via unknown mechanisms. To quickly assess these drugs for their potential toxicological effects and mechanisms, we used the Tox21 in vitro assay datasets generated from screening ∼10,000 compounds consisting of approved drugs and environmental chemicals against multiple cellular targets and pathways. Here we summarize the toxicological profiles of small molecule drugs that are currently under clinical trials for the treatment of COVID-19 based on their in vitro activities against various targets and cellular signaling pathways.

Anticholinesterase Inhibition, Drug-Likeness Assessment, and Molecular Docking Evaluation of Milk Protein-Derived Opioid Peptides for the Control of Alzheimer’s Disease

The drug-likeness and pharmacokinetic properties of 23 dairy-protein-derived opioid peptides were studied using SwissADME and ADMETlab in silico tools. All the opioid peptides had poor drug-like properties based on violations of Lipinski’s rule-of-five. Moreover, prediction of their pharmacokinetic properties showed that the peptides had poor intestinal absorption and bioavailability. Following this, two well-known opioid peptides (βb-casomorphin-5, βb-casomorphin-7) from A1 bovine milk and caffeine (positive control) were selected for in silico molecular docking and in vitro inhibition study with two cholinesterase enzyme receptors important for the pathogenesis of Alzheimer’s disease. Both peptides showed higher binding free energies and inhibitory activities to butyrylcholinesterase (BChE) than caffeine, but in vitro binding energy values were lower than those from the docking model. Moreover, the two casomorphins had lower inhibitory properties against acetylcholinesterase (AChE) than caffeine, although the docking model predicted the opposite. At 1 mg/mL concentrations, βb-casomorphin-5 and βb-casomorphin-7 showed promising results in inhibiting both cholinesterases (i.e., respectively 34% and 43% inhibition of AChE, and 67% and 81% inhibition of BChE). These dairy-derived opioid peptides have the potential to treat Alzheimer’s disease via cholinesterase inhibition. However, appropriate derivatization may be required to improve their poor predicted intestinal absorption and bioavailability.

Chemical Composition, Biological Activities and In Silico Analysis of Essential Oils of Three Endemic Prangos Species from Turkey

In this study, the essential oils (EOs) obtained from three endemic Prangos species from Turkey (P. heyniae, P. meliocarpoides var. meliocarpoides, and P. uechtritzii) were studied for their chemical composition and biological activities. β-Bisabolenal (12.2%) and caryophyllene oxide (7.9%) were the principal components of P. heyniae EO, while P. meliocarpoides EO contained sabinene (16.7%) and p-cymene (13.2%), and P. uechtritzii EO contained p-cymene (24.6%) and caryophyllene oxide (19.6%), as the most abundant components. With regard to their antioxidant activity, all the EOs were found to possess free radical scavenging potential demonstrated in both DPPH and ABTS assays (0.43–1.74 mg TE/g and 24.18–92.99 mg TE/g, respectively). Additionally, while no inhibitory activity was displayed by P. meliocarpoides and P. uechtritzii EOs against both cholinesterases (acetyl- and butyryl-cholinesterases). Moreover, all the EOs were found to act as inhibitors of tyrosinase (46.34–69.56 mg KAE/g). Molecular docking revealed elemol and α-bisabolol to have the most effective binding affinity with tyrosinase and amylase. Altogether, this study unveiled some interesting biological activities of these EOs, especially as natural antioxidants and tyrosinase inhibitors and hence offers stimulating prospects of them in the development of anti-hyperpigmentation topical formulations.