Acetylcholinesterase Sensor Based on Polyelectrolyte Complexes with DNA Inclusion for the Determination of Reversible Inhibitors

The acetylcholinesterase (AChE) biosensor has been developed for the determination of reversible inhibitors applied in the Alzheimer's disease therapy, i. e., Huperzine A (HupA) and galantamine (Gal). For this purpose, glassy carbon electrode (GCE) was first modified with carbon black (CB) and Co phthalocyanine and then polyelectrolyte complex was self‐assembled on its surface by drop casting of reactants and washing. To extend the stability and improve biosensor performance, it was proposed for the first time to use DNA as polyanion in the complex assembly. The DNA showed higher charge density than conventional polyelectrolytes and stabilized the surface coating by adsorption of higher enzyme amount and prevention of its leaching during the biosensor operation. Complex formation and the influence of structural factors were monitored with surface plasmon resonance. Kinetic study showed mixed inhibition of the enzyme within micro‐ and nanomolar range of inhibitor concentrations. The AChE biosensor showed limit of detection of HupA equal to 0.9 and that of Gal to 70 nM. The sensitivity of drug determination was found to be close or better than that of the AChE biosensors previously reported in the literature. The biosensor was tested on the sample of artificial urine and showed 102 % recovery of the drugs determination.     

Extraction and isolation of acetylcholinesterase inhibitors from Citrus limon peel using an in vitro method

A simple and efficient ultrafiltration–liquid chromatography–mass spectrometry–based method was developed for the rapid screening and identification of ligands from Citrus limon peel, which are suitable acetylcholinesterase inhibitors. Subsequently, the anti‐Alzheimer's activity of these compounds was assessed using a PC12 cell model. Six major compounds, viz. neoeriocitrin, isonaringin, naringin, hesperidin, neohesperidin, and limonin, were identified as potent acetylcholinesterase inhibitors. A continuous and efficient online method, which involved the use of a microwave‐assisted extraction device, solvent concentration tank, and centrifugal partition chromatography column, was developed for the scale‐up of these compounds, and the obtained compounds presented high purity. Next, their bioactivity was evaluated using a PC12 cell model. This novel approach, which was based on ultrafiltration–liquid chromatography–mass spectrometry, microwave‐assisted extraction online coupled with solvent concentration tank, and centrifugal partition chromatography along with in vitro evaluation, could represent a powerful tool for the screening and extraction of acetylcholinesterase inhibitors from complex matrices, and could be a useful platform for the large‐scale production of bioactive and nutraceutical ingredients.     

A simple, rapid and sensitive method for simultaneous determination of rivastigmine and its major metabolite NAP 226-90 in rat brain and plasma by reversed-phase liquid chromatography coupled to electrospray ionization mass spectrometry

A simple and sensitive reversed-phase liquid chromatography coupled with electrospray-mass spectrometry was developed and validated for the simultaneous determination of rivastigmine, a cholinesterase inhibitor, and its major metabolite NAP 226-90 in rat plasma and brain homogenates. Rivastigmine and NAP 226-90 were extracted from plasma and brain by ethyl acetate and, after drying under nitrogen, re-dissolved in acetonitrile and separated isocratic by HPLC on a C(18) column and quantified by single ion monitoring mass spectrometer. The mean (+/-SD) extraction efficiency for rivastigmine in plasma and brain was 93 +/- 2 and 95 +/- 2% (n = 5) of NAP 226-90 in a drug range of 10-100 pmol/mL or pmol/g. The method proved to be linear within the tested range (regression coefficient, r = 0.9999, n = 5). Intra- and inter-day precision coefficients of variation and accuracy bias were acceptable (within 15%, n = 5) over the entire range for both compounds using plasma or brain samples. The limits of quantification were 0.5 pmol/mL plasma and 2.5 pmol/g brain for rivastigmine and 1 pmol/mL plasma and 5 pmol/g brain for NAP 226-90, respectively. The analytical technique was used to determine the concentrations of rivastigmine and its metabolite NAP 226-90 in rat plasma and brain after oral drug administration. The concentrations of the parent drug and its major metabolite were compared to a pharmacodynamic parameter, the ex vivo inhibition of acetylcholinesterase.     

Solvent‐Free Synthesis of Arylamides and Arylimides,Analogues of Acetylcholine

Abstract

Several arylamides and arylimides, novel inhibitors of acetylcholinesterase, were obtained under solventless conditions; the target molecules were produced with a good overall yield and short reaction times.     

New Synthesis of Donepezil Through Palladium‐Catalyzed Hydrogenation Approach

A new, economical, and efficient process has been developed for large‐scale synthesis of donepezil 1, an anti‐Alzheimer's drug. The process involves palladium‐catalyzed hydrogenation of (2E)‐5,6‐dimethoxy‐2‐(pyridin‐4‐ylmethylene)indan‐1‐one 6 to provide 5,6‐dimethoxy‐2‐(piperidin‐4‐ylmethyl)indan‐1‐one 8 as a key step.     

Experimental and Theoretical Approaches in the Study of Phenanthroline-Tetrahydroquinolines for Alzheimer's Disease

The imino-Diels-Alder reaction is one of the most common strategies in organic chemistry and is an important tool for providing a broad spectrum of biologically active heterocyclic systems. A combined theoretical and experimental study of the imino-Diels-Alder reaction is described. The new phenanthroline-tetrahydroquinolines were evaluated as cholinesterase inhibitors. Their cytotoxicity in human neuroblastoma SH-SY5Y cells was also evaluated. The theoretical results suggest that compounds formation in stages can be explained by endo cycloadducts under the established reaction conditions, thereby confirming experimental results obtained for percentage yield. These results allowed us to establish that pyridine substituent remarkably influences activation energy and reaction yield, as well as in acetylcholinesterase (AChE) activity. Among these derivatives, compounds with 4-pyridyl and 4-nitrophenyl showed favorable AChE activity and proved to be non-cytotoxic.     

Alzheimer's Disease: From Pathology to Therapeutic Approaches

Mind how you go : The current strategies for the development of therapies for Alzheimer's disease are very diverse. Particular attention is given to the search for inhibitors (see picture for two examples) of the proteolytic enzyme β‐ and γ‐secretase, which inhibits the cleavage of the amyloid precursor proteins into amyloid β peptides, from which the disease‐defining deposits of plaque in the brains of Alzheimer's patients originates.

     

Tyrosol 1,2,3-triazole analogues as new acetylcholinesterase (AChE) inhibitors

The present work proposed the preparation of triazolic analogues of tyrosol, a biophenol found in olive oil and whose wide range of bioactivities has been the target of many studies. We obtained fifteen novel tyrosol derivatives and the compounds of the series were later evaluated as acetylcholinesterase (AChE) inhibitors. The study of AChE inhibition is important for the development of new drugs and pesticides, and especially the research for managing Alzheimer's disease. The most active compound, namely 7-({1-[2-(4-hydroxyphenyl)ethyl]-1H-1,2,3-triazol-4-yl}methoxy)-4-methyl-2H-chromen-2-one (30), showed IC₅₀ value of 14.66 ± 2.29 μmol L⁻¹. Docking experiments corroborated by kinetic assay are suggestive of a competitive inhibition mechanism. Derivatives interacted with amino acids from the AChE active site associated to the development of Alzheimer's disease. The results indicate that the compounds synthesized have a high potential as prototypes for the development of new acetylcholinesterase inhibitors.     

Design,Synthesis, and Evaluation of Bioactive Small Molecules

Collaborative research projects between chemists, biologists, and medical scientists have inevitably produced many useful drugs, biosensors, and medical instrumentation. Organic chemistry lies at the heart of drug discovery and development. The current range of organic synthetic methodologies allows for the construction of unlimited libraries of small organic molecules for drug screening. In translational research projects, we have focused on the discovery of lead compounds for three major diseases: Alzheimer's disease (AD), breast cancer, and viral infections. In the AD project, we have taken a rational‐design approach and synthesized a new class of tricyclic pyrone (TP) compounds that preserve memory and motor functions in amyloid precursor protein (APP)/presenilin‐1 (PS1) mice. TPs could protect neuronal death through several possible mechanisms, including their ability to inhibit the formation of both intraneuronal and extracellular amyloid β (Aβ) aggregates, to increase cholesterol efflux, to restore axonal trafficking, and to enhance long‐term potentiation (LTP) and restored LTP following treatment with Aβ oligomers. We have also synthesized a new class of gap‐junction enhancers, based on substituted quinolines, that possess potent inhibitory activities against breast‐cancer cells in vitro and in vivo. Although various antiviral drugs are available, the emergence of viral resistance to existing antiviral drugs and various understudied viral infections, such as norovirus and rotavirus, emphasizes the demand for the development of new antiviral agents against such infections and others. Our laboratories have undertaken these projects for the discovery of new antiviral inhibitors. The discussion of these aforementioned projects may shed light on the future development of drug candidates in the fields of AD, cancer, and viral infections.     

A reversed‐phase compatible thin‐layer chromatography autography for the detection of acetylcholinesterase inhibitors

A dual readout autographic assay to detect acetylcholinesterase inhibitors present in complex matrices adsorbed on reversed‐phase or normal‐phase thin‐layer chromatography plates is described. Enzyme gel entrapment with an amphiphilic copolymer was used for assay development. The effects of substrate and enzyme concentrations, pH, incubation time, and incubation temperature on the sensitivity and the detection limit of the assay were evaluated. Experimental design and response surface methodology were used to optimize conditions with a minimum number of experiments. The assay allowed the detection of 0.01% w/w of physostigmine in both a spiked Sonchus oleraceus L. extract chromatographed on normal phase and a spiked Pimenta racemosa (Mill.) J.W. Moore leaf essential oil chromatographed on reversed phase. Finally, the reversed‐phase thin‐layer chromatography assay was applied to reveal the presence of an inhibitor in the Cymbopogon citratus (DC.) Stapf essential oil. The developed assay is able to detect acetylcholinesterase inhibitors present in complex matrixes that were chromatographed in normal phase or reversed‐phase thin‐layer chromatography. The detection limit for physostigmine on both normal and reversed phase was of 1×10^?4 μg. The results can be read by a change in color and/or a change in fluorescence.     

Modified TLC bioautographic method for screening acetylcholinesterase inhibitors from plant extracts

The present work describes modifications to an existing TLC bioautographic method for detecting acetylcholinesterase inhibitors from plant extracts. The basic principle of the method is that the enzyme converts 1‐naphthyl acetate into naphthol which reacts with Fast Blue B salt to make a purple‐colored background on the TLC plates. Inhibitors of acetylcholinesterases produced white spots on the background. Our modifications involve changes in the concentration of the enzyme, the reagents, and the time of the reaction. With these changes, the consumption of the enzyme was reduced by 85% and the detection limits were decreased remarkably.     

Amyloid Aggregates,Presenilins, and Alzheimer's Disease

The cooperative action of three proteases is required to process the APP protein (695–770 amino acids) into small β-amyloid peptides (Aβ, 40–42 amino acids). Aβ aggregates are found in the senile plaques of patients with Alzheimer's disease and play a major role in the onset of this disorder. The functional analysis of several factors that contribute to the production and aggregation of Aβ has enhanced our knowledge of the mechanism of amyloid formation and increased the potential for effective therapeutic treatment.     

Dual inhibitors of Interleukin-6 and acetylcholinesterase for treatment of Alzheimer's disease: Design,docking, synthesis and biological evaluation

Multitarget compounds intercept two or more functionally complementary pathways simultaneously, and are therefore considered to have potential in effectively treating complex multifactorial diseases like Alzheimer's disease (AD). In the present study, novel molecules are designed by coupling a chromone and a N,N-disubstituted carbamoyl amine as pharmacophore for interleukin-6 (IL-6) and acetylcholinesterase (AChE) inhibition, respectively. Four series (Y1–Y4) of 40 compounds are designed by using alkyl linkers of different lengths (1–4 carbon atoms) for the coupling of the two selected pharmacophore. Docking of all designed compounds in AChE leads to the identification of twelve best fit compounds (Docking score >8.3). The data suggests that a 1- or 2-carbon atom linker is the most conducive to orient the pharmacophore for optimum binding with AChE active site. The predicted ADME properties of the 12 selected compounds suggest that these can cross the blood brain barrier (BBB) with good oral bioavailability. These compounds are synthesised and evaluated for anti-AChE activity. Five compounds, showing >45% inhibition of AChE, are further evaluated for IL-6 inhibitory activity. Compound Y1f is found to be the most potent inhibitor of both AChE and IL-6 (IC₅₀ 0.7 and 0.8 ​μM, respectively). It suggests that a chromone moiety connected to a piperidine ring through a 1-carbon atom linker may provide a useful template to medical chemists for the development of new chemical entities effective against AD.     

Donepezil hydrochloride: a treatment drug for Alzheimer's disease

The role of the cholinergic system with respect to cognitive deficits characteristic of Alzheimer's disease (AD) has led to a number of studies focusing on the development of acetylcholinesterase (AChE) inhibitors as a drug for treating this disease. The earliest known AChE inhibitors, namely, physostigmine and tacrine, performed poorly in clinical trials (e.g., poor oral activity, brain penetration, and hepatotoxic liability). Studies were then focused on finding a new type of acetylcholinesterase inhibitor that would overcome the disadvantages of these two compounds. Donepezil hydrochloride inaugurates a new class of AChE inhibitors with longer and more selective action and with manageable adverse effects.     

Rapid methods for the separation of natural mixtures of beauverolides,cholesterol acyltransferase inhibitors,isolated from the fungus Isaria fumosorosea

Beauverolides (beauveriolides) are abundant, biologically active cyclodepsipeptides produced by many entomopathogenic fungi, including those that are used as biopesticides. Beauverolides act as cholesterol acyltransferase inhibitors in humans; thus, their mode of action has been the subject of pharmacological and clinical research. The cost‐effective analytical methods are needed for fast, routine laboratory analysis of beauverolides. We isolated beauverolides from the fungal strain Isaria fumosorosea PFR 97‐Apopka and opened the rings of the isolated beauverolides using a pyridine alkaline medium. We separated fractions of cyclic and linearized beauverolides by thin‐layer chromatography, and found the chloroform–acetate (9:1, v/v) and chloroform–acetonitrile–acetate (8:1:1, v/v/v) mobile phases, respectively, to be the most efficient. We examined all the fractions by liquid chromatography–mass spectrometry using ion trap and Orbitrap high resolution mass spectrometry. For rapid screening of the contents of cyclic, and, particularly, linearized beauverolides, we developed a novel analytical method that consisted of using capillary electrophoresis coupled with contactless conductivity detection. Furthermore, we improved the separation of the peptides by applying capillary micellar electrokinetic chromatography with the N‐cyclohexyl‐2‐aminoethanesulfonic acid:SDS:NaOH buffer, pH 9.8 as the background electrolyte. The described novel methods allow fast and cost‐effective separation of chemically related groups of beauverolides.     

GC-MS Metabolic Profile and α-Glucosidase-, α-Amylase-, Lipase-, and Acetylcholinesterase-Inhibitory Activities of Eight Peach Varieties

The inhibition of certain digestive enzymes by target food matrices represents a new approach in the treatment of socially significant diseases. Proving the ability of fruits to inhibit such enzymes can support the inclusion of specific varieties in the daily diets of patients with diabetes, obesity, Alzheimer’s disease, etc., providing them with much more than just valuable micro- and macromolecules. The current study aimed atidentifying and comparing the GC-MS metabolic profiles of eight peach varieties (“Filina”, “Ufo 4, “Gergana”, “Laskava”, “July Lady”, “Flat Queen”, “Evmolpiya”, and “Morsiani 90”) grown in Bulgaria (local and introduced) and to evaluate the inhibitory potential of their extracts towards α-glucosidase, α-amylase, lipase, and acetylcholinesterase. In order to confirm samples’ differences or similarities, principal component analysis (PCA) and hierarchical cluster analysis (HCA) were also applied to the identified metabolites. The results provide important insights into the metabolomic profiles of the eight peach varieties and represent a first attempt to characterize the peels of the peach varieties with respect to α-glucosidase-, α-amylase-, lipase-, and acetylcholinesterase-inhibitory activities. All of the studied peach extracts displayed inhibitory activity towards α-glucosidase (IC₅₀: 125–757 mg/mL) and acetylcholinesterase (IC₅₀: 60–739 mg/mL), but none of them affected α-amylase activity. Five of the eight varieties showed inhibitory activity towards porcine pancreatic lipase (IC₅₀: 24–167 mg/mL). The obtained results validate the usefulness of peaches and nectarines as valuable sources of natural agents beneficial for human health, although further detailed investigation should be performed in order to thoroughly identify the enzyme inhibitors responsible for each activity.     

Natural product inhibitors as potential drug candidates against Alzheimer's disease: Structural-based drug design,molecular docking,molecular dynamic simulation experiments,and ADMET predictions

Alzheimer's disease (AD) is currently an incurable ailment with complicated-mechanism that causes intellectual impairment in adults mostly from 65 years old and above. Hence, immediate effort and actions are required to prevent or cure this life-threatening disease. There are currently four medications in the market, all of which have minimal therapeutic potential and are quite hazardous. The familiar pharmacological targets and intervention principles were assessed using an in-silico technique. This strategy emphasizes the benefits of natural products operating in a polytherapeutic manner over a monotherapy approach to AD treatment. A protein target with ID code 4EY7 was utilized in this research and it was chosen based on established literature studies and reasons such as lower resolution value (2.3Å), no mutation, Homo Sapiens, and X-ray diffraction method, the protein target interacted with some natural products, with greater interactions, higher binding scores, and improved enhanced drug-like properties and drug kinetic parameters The findings of these studies can be used to design promising pharmacotherapeutic compounds for the treatment of ADNatural products were docked with protein targets, resulting in a molecule with the maximum binding energy of −19.82 kcalmol^-1. It was utilized as a template for designing natural product derivatives with lower binding energies, high stability, and improved interactions. Compound Y5 has a docking score of −26.29 kcalmol^-1. The molecular dynamics (MD) Simulation used docked protein complexes with selected ligands as standard (reference) further verified the docking results. RSMD showed that compound Y5 remain within the inhibitor binding site all through the simulation period and reached equilibrium more rapidly compared to the standard. Also, the RMSF, Rg curve, and SASA gives brilliant results which further confirmed the stability of compound Y5. Lastly, the ligand hydrogen bond was examined, compound Y5 formed more hydrogen bonds with protein during the 100ns simulation indicating that the compound Y5 complex was more stable relative to the harmine. The compounds' drug-likeness and pharmacokinetics features were also evaluated, and all showed positive results. Alzheimer's as a consequence, these designed compounds with variety of inherent endowment of therapeutic ability and support in successful research and development, leading to excellent therapeutic effects, low toxicity, and brilliant kinetic abilities, making substantial contributions to the treatment of AD.     

Atomic‐Resolution Three‐Dimensional Structure of Amyloid β Fibrils Bearing the Osaka Mutation

Despite its central importance for understanding the molecular basis of Alzheimer's disease (AD), high‐resolution structural information on amyloid β‐peptide (Aβ) fibrils, which are intimately linked with AD, is scarce. We report an atomic‐resolution fibril structure of the Aβ1‐40 peptide with the Osaka mutation (E22Δ), associated with early‐onset AD. The structure, which differs substantially from all previously proposed models, is based on a large number of unambiguous intra‐ and intermolecular solid‐state NMR distance restraints.     

苯并噻唑功能化的金属螯合剂的合成及生物活性

设计、合成了2种苯并噻唑功能化的金属螯合剂:N,N′-双(水杨醛)缩-2,2′-(3-(苯并[d]噻唑-2-基)-1,2-苯基)二氧乙基二胺L1和N,N′-双(水杨醛)缩-2,2′-(4-(苯并[d]噻唑-2-基)-1,2-苯基)二氧乙基二胺L2。并通过比浊度分析、BCA实验、HRP/Amplex Red实验以及MTT实验检测它们的生物活性。发现这2种螯合剂都能有效抑制金属离子(Zn~(2+)、Cu~(2+))诱导的Aβ_(1～40)的聚集,能大幅减少Cu-Aβ加合物产生H_2O_2的量,有效抑制Zn~(2+)、Cu~(2+)诱导Aβ聚集而产生的神经细胞毒性,并大幅提高细胞存活率。作为比较,对非苯并噻唑功能化但螯合部位相同的螯合剂做了相同的生物活性测试,但其生物活性明显比苯并噻唑功能化的金属螯合剂的低。