Lead optimization based design, synthesis, and pharmacological evaluation of quinazoline derivatives as multi-targeting agents for Alzheimer's disease treatment.

The complexity and multifaceted nature of Alzheimer's disease (AD) have driven us to further explore quinazoline scaffolds as multi-targeting agents for AD treatment. The lead optimization strategy was utilized in designing of new series of derivatives (AK-1 to AK-14) followed by synthesis, characterization, and pharmacological evaluation against human cholinesterase's (hChE) and ß-secretase (hBACE-1) enzymes. Amongst them, compounds AK-1, AK-2, and AK-3 showed good and significant inhibitory activity against both hAChE and hBACE-1 enzymes with favorable permeation across the blood-brain barrier. The most active compound AK-2 revealed significant propidium iodide (PI) displacement from the AChE-PAS region and was non-neurotoxic against SH-SY5Y cell lines. The lead molecule (AK-2) also showed Aß aggregation inhibition in a self- and AChE-induced Aß aggregation, Thioflavin-T assay. Further, compound AK-2 significantly ameliorated Aß-induced cognitive deficits in the Aß-induced Morris water maze rat model and demonstrated a significant rescue in eye phenotype in the Aꞵ-phenotypic drosophila model of AD. Ex-vivo immunohistochemistry (IHC) analysis on hippocampal rat brains showed reduced Aß and BACE-1 protein levels. Compound AK-2 suggested good oral absorption via pharmacokinetic studies and displayed a good and stable ligand-protein interaction in in-silico molecular modeling analysis. Thus, the compound AK-2 can be regarded as a lead molecule and should be investigated further for the treatment of AD.

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

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

Design, Synthesis, and Biological Investigation of Quinazoline Derivatives as Multitargeting Therapeutics in Alzheimer's Disease Therapy.

An efficient and promising method of treating complex neurodegenerative diseases like Alzheimer's disease (AD) is the multitarget-directed approach. Here in this work, a series of quinazoline derivatives (AV-1 to AV-21) were rationally designed, synthesized, and biologically evaluated as multitargeted directed ligands against human cholinesterase (hChE) and human ß-secretase (hBACE-1) that exhibit moderate to good inhibitory effects. Compounds AV-1, AV-2, and AV-3 from the series demonstrated balanced and significant inhibition against these targets. These compounds also displayed excellent blood-brain barrier permeability via the PAMPA-BBB assay. Compound AV-2 significantly displaced propidium iodide (PI) from the acetylcholinesterase-peripheral anionic site (AChE-PAS) and was found to be non-neurotoxic at the maximum tested concentration (80 µM) against differentiated SH-SY5Y cell lines. Compound AV-2 also prevented AChE- and self-induced Aß aggregation in the thioflavin T assay. Additionally, compound AV-2 significantly ameliorated scopolamine and Aß-induced cognitive impairments in the in vivo behavioral Y-maze and Morris water maze studies, respectively. The ex vivo and biochemical analysis further revealed good hippocampal AChE inhibition and the antioxidant potential of the compound AV-2. Western blot and immunohistochemical (IHC) analysis of hippocampal brain revealed reduced Aß, BACE-1, APP/Aß, and Tau molecular protein expressions levels. The pharmacokinetic analysis of compound AV-2 demonstrated significant oral absorption with good bioavailability. The in silico molecular modeling studies of lead compound AV-2 moreover demonstrated a reasonable binding profile with AChE and BACE-1 enzymes and stable ligand-protein complexes throughout the 100 ns run. Compound AV-2 can be regarded as the lead candidate and could be explored more for AD therapy.

Identifying inflammation-related targets of natural lactones using network pharmacology, molecular modeling and in vitro approaches.

Natural lactones have been used in traditional and folklore medicine for centuries owing to their anti-inflammatory properties. The study uses a multifaceted approach to identify lead anti-inflammatory lactones from the SISTEMATX natural products database. The study analyzed the natural lactone database, revealing 18 lactones linked to inflammation targets. The primary targets were PTGES, PTGS1, COX-2, ALOX5 and IL1B. STX 12273 was the best hit, with the lowest binding energy and potential for inhibiting the COX-2 enzyme. The study suggested natural lactone, STX 12273, from the SISTEMATX database with anti-inflammatory potential and postulated its use for inflammation treatment or prevention.Communicated by Ramaswamy H. Sarma.

Hydroxamic acid derivatives as selective HDAC3 inhibitors: computer-aided drug design strategies.

Histone deacetylases (HDACs) are critical epigenetic drug targets that have gained significant attention in the scientific community for the treatment of cancer. The currently marketed HDAC inhibitors lack selectivity for the various HDAC isoenzymes. Here, we describe our protocol for the discovery of novel potential hydroxamic acid based HDAC3 inhibitors through pharmacophore modeling, virtual screening, docking, molecular dynamics (MD) simulation and toxicity studies. The ten pharmacophore hypotheses were established, and their reliability was validated by different ROC (receiving operator curve) analysis. Among them, the best model (Hypothesis 9 or RRRA) was employed for searching SCHEMBL, ZINC and MolPort database to screen out hit molecules as selective HDAC3 inhibitors, followed by different docking stages. MD simulation (50 ns) and MMGBSA study were performed to study the stability of ligand binding modes and with the help of trajectory analysis, to calculate the ligand-receptor complex RMSD (root-mean-square deviation), RMSF (root-mean-square fluctuation) and H-bond distance, etc. Finally, in-silico toxicity studies were performed on top screened molecules and compared with reference drug SAHA and established structure-activity relationship (SAR). The results indicated that compound 31, with high inhibitory potency and less toxicity (probability value 0.418), is suitable for further experimental analysis.Communicated by Ramaswamy H. Sarma.

Pharmacophore modeling and virtual screening were performed with hydroxamic acid derivatives as HDAC3 inhibitors.MD simulation was performed for 50 ns time duration for selected protein-ligand complexes.SAR and toxicity studies (using TOPKAT tool) were performed.The results of these studies might be valuable in the further design and development of more potent HDAC3 inhibitors.

Design and development of benzyl piperazine linked 5-phenyl-1,2,4-triazole-3-thione conjugates as potential agents to combat Alzheimer's disease.

Our present work demonstrates the molecular hybridization-assisted design, synthesis, and biological evaluation of 22 benzylpiperazine-linked 1,2,4-triazole compounds (PD1-22) as AD modifying agents. All the compounds were tested for their in vitro hChEs, hBACE-1, and Aß-aggregation inhibition properties. Among them, compound PD-08 and PD-22 demonstrated good hChE and hBACE-1 inhibition as compared to standards donepezil and rivastigmine. Both compounds displaced PI from PAS at 50 µM concentration which was comparable to donepezil and also demonstrated anti-Aß aggregation properties in self- and AChE-induced thioflavin T assay. Both compounds have shown excellent BBB permeation via PAMPA-BBB assay and were found to be non-neurotoxic at 80 µM concentration against differentiated SH-SY5Y cell lines. Compound PD-22 demonstrated an increase in rescued eye phenotype in Aß-phenotypic drosophila AD model and amelioration of behavioral deficits in the Aß-induced rat model of AD. The in-silico docking studies of compound PD-22 revealed a good binding profile towards CAS and PAS residues of AChE and the catalytic dyad of the BACE-1. The 100 ns molecular dynamics simulation studies of compound PD-22 complexed with AChE and BACE-1 enzymes suggested stable ligand-protein complex throughout the simulation run. Based on our findings compound PD-22 could further be utilized as a lead to design a promising candidate for AD therapy.

Design, Synthesis, and Biological Evaluation of Piperazine and N-Benzylpiperidine Hybrids of 5-Phenyl-1,3,4-oxadiazol-2-thiol as Potential Multitargeted Ligands for Alzheimer's Disease Therapy.

Our present work demonstrates the successful design and synthesis of a new class of compounds based upon a multitargeted directed ligand design approach to discover new agents for use in Alzheimer's disease (AD). All the compounds were tested for their in vitro inhibitory potential against human acetylcholinesterase (hAChE), human butylcholinesterase (hBChE), ß-secretase-1 (hBACE-1), and amyloid ß (Aß) aggregation. Compounds 5d and 5f have shown hAChE and hBACE-1 inhibition comparable to donepezil, while hBChE inhibition was comparable to rivastigmine. Compounds 5d and 5f also demonstrated a significant reduction in the formation of Aß aggregates through the thioflavin T assay and confocal, atomic force, and scanning electron microscopy studies and significantly displaced the total propidium iodide, that is, 54 and 51% at 50 µM concentrations, respectively. Compounds 5d and 5f were devoid of neurotoxic liabilities against RA/BDNF (RA = retinoic acid; BDNF = brain-derived neurotrophic factor)-differentiated SH-SY5Y neuroblastoma cell lines at 10-80 µM concentrations. In both the scopolamine- and Aß-induced mouse models for AD, compounds 5d and 5f demonstrated significant restoration of learning and memory behaviors. A series of ex vivo studies of hippocampal and cortex brain homogenates showed that 5d and 5f elicit decreases in AChE, malondialdehyde, and nitric oxide levels, an increase in glutathione level, and reduced levels of pro-inflammatory cytokines, tumor necrosis factor alpha (TNF-α) and interleukin-6 (IL-6) mRNA. The histopathological examination of mice revealed normal neuronal appearance in the hippocampal and cortex regions of the brain. Western blot analysis of the same tissue indicated a reduction in Aß, amyloid precursor protein (APP)/Aß, BACE-1, and tau protein levels, which were non-significant compared to the sham group. The immunohistochemical analysis also showed significantly lower expression of BACE-1 and Aß levels, which was comparable to donepezil-treated group. Compounds 5d and 5f represent new lead candidates for developing AD therapeutics.

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

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

In silico and in vitro evaluation of extract derived from Dunaliella salina, a halotolerant microalga for its antifungal and antibacterial activity.

In the present study little explored halotolerant wall-less green alga Dunaliella salina was found to be a potent source of antibacterial and antifungal biomolecules. Both the target pathogens, bacteria (Escherischia coli, Klebsiella pneumoniae, and Acinetobacter baumannii) and fungi (Candida albicans, C. tropicalis, and Cryptococus sp.) were WHO prioritized. The bioassay guided approach led us to evaluate antibacterial and antifungal lead molecule(s) from an array of compounds using spectroscopic and in silico studies. The methanol derived crude extract was purified via thin layer chromatography (TLC) using solvent system methanol: chloroform (1:19). Maximum antimicrobial activity was observed in fractions D5, D6 and D7, the components of which were then recognized using high resolution-liquid chromatography/mass spectroscopy (Orbitrap) (HR-LC/MS). The screened compounds were then docked with target enzymes sterol-14-alpha demethylase and OmpF porin protein. The energy scores revealed that amongst all, lariciresinol-4-O-glucoside showed better binding affinity, in silico, using the Schrödinger Maestro 2018-1 platform. The 3-dimensional crystal structures of both the proteins were retrieved from the protein data bank (PDB), and showed binding energies of -14.35 kcal/mol, and -11.0 kcal/mol against respective drug targets. The molecular dynamics (MD) simulations were performed for 100 ns, using Desmond package, Schrödinger to evaluate the conformational stability and alteration of protein-ligand complexes during the simulation. Thus, our findings confirmed that lariciresinol-4-O-glucoside, a lignan derivative and known strong antioxidant, may be used as an important "lead" molecule to be developed as antibacterial and antifungal drugs in the future.Communicated by Ramaswamy H. Sarma.

Design, synthesis, and evaluation of N-benzylpyrrolidine and 1,3,4-oxadiazole as multitargeted hybrids for the treatment of Alzheimer's disease.

Novel N-Benzylpyrrolidine hybrids were designed, synthesized, and tested against multiple in-vitro and in-vivo parameters. Among all the synthesized molecules, 8f and 12f showed extensive inhibition against beta-secretase-1 (hBACE-1), human acetylcholinesterase (hAChE) & human butyrylcholinesterase (hBuChE). These molecules are also endowed with significant AChE-peripheral anionic site (PAS) binding capability, blood-brain barrier permeability, potential disassembly of Aß aggregates along with neuroprotection ability on SHSY-5Y cell lines. Results of the Y-Maze and Morris water maze test concluded that compounds 8f and 12f ameliorated cognitive dysfunction induced by scopolamine and Aß. The ex-vivo activity was executed on rat's brain homogenate indicating a reduction in AChE level and oxidative stress. The pharmacokinetic investigation ascertained considerable oral absorption profile of the lead 12f. The results of the in silico docking studies and molecular dynamics simulations demonstrated stable interactions of compounds 8f and 12f with the target residues of hAChE, hBuChE and hBACE-1.

Design, synthesis, and multitargeted profiling of N-benzylpyrrolidine derivatives for the treatment of Alzheimer's disease.

Multitarget molecular hybrids of N-benzyl pyrrolidine derivatives were designed, synthesized, and biologically evaluated for the treatment of Alzheimer's disease (AD). Among the synthesized compounds, 4k and 4o showed balanced enzyme inhibitions against cholinesterases (AChE and BChE) and BACE-1. Both leads showed considerable PAS-AChE binding capability, excellent brain permeation, potential disassembly of Aß aggregates, and neuroprotective activity against Aß-induced stress. Compounds 4k and 4o also ameliorated cognitive dysfunction against the scopolamine-induced amnesia model in the Y-maze test. The ex vivo study signified attenuated brain AChE activity and antioxidant potential of compounds 4k and 4o. Furthermore, compound 4o also showed improvement in Aß-induced cognitive dysfunction by the Morris water maze test with excellent oral absorption characteristics ascertained by the pharmacokinetic study. In silico molecular docking and dynamics simulation studies of leads suggested their consensual binding affinity toward PAS-AChE in addition to aspartate dyad of BACE-1.

Computational exploration and experimental validation to identify a dual inhibitor of cholinesterase and amyloid-beta for the treatment of Alzheimer's disease.

The cholinesterases are essential targets implicated in the pathogenesis of Alzheimer's disease (AD). In the present study, virtual screening and molecular docking are performed to identify the potential hits. Docking-post processing (DPP) and pose filtration protocols against AChE and BChE resulted in three hits (AW00308, HTS04089, and JFD03947). Molecular Mechanics-Generalized Born Surface Area (MM-GBSA) and molecular dynamics simulation analysis affirmed the stability and binding pattern of the docked complex JFD03947, which was further synthesized and evaluated for in vitro cholinesterase inhibition (AChE, IC50 = 0.062 µM; BChE, IC50 = 1.482 µM) activity. The enzyme kinetics study of the JFD03947 against hAChE and hBChE suggested a mixed type of inhibition. The results of thioflavin T-assay also elicited anti-Aß aggregation activity by JFD03947. Further, biological evaluation of identified compound JFD03947 also showed neuroprotective ability against the SH-SY5Y neuroblastoma cell lines.

Design, synthesis, and biological evaluation of ferulic acid based 1,3,4-oxadiazole hybrids as multifunctional therapeutics for the treatment of Alzheimer's disease.

Thirty ferulic acid-based 1,3,4-oxadiazole molecular hybrids were designed, synthesized, and screened them for multifunctional inhibitory potential against acetylcholinesterase (AChE), butyrylcholinesterase (BChE) and beta-secretase-1 (BACE-1). Compound 6j was the most potent inhibitor of AChE (IC50 = 0.068 µM). It also showed equipotent inhibition of BChE and BACE-1 with IC50 values of 0.218 µM and 0.255 µM, respectively. Compound 6k possessed the most significant inhibition of BChE and BACE-1 with IC50 values, 0.163 µM and 0.211 µM, respectively. Compounds 6j and 6k elicited significant displacement of propidium iodide from PAS-AChE, excellent BBB permeability in PAMPA assay, and anti-Aß aggregatory activity in self- and AChE-induced experiments with neuroprotective activity towards neuroblastoma SH-SY5Y cells. The in vivo behavioral studies suggested amelioration of cognitive dysfunction by 6j and 6k in the Y maze test. The ex vivo study signified brain AChE inhibition and antioxidant activity from these compounds. Moreover, 6j showed improvement in learning and memory behavior in the Aß-induced ICV rat model by Morris water maze test with excellent oral absorption characteristics ascertained by pharmacokinetic studies.

Cholinesterase as a Target for Drug Development in Alzheimer's Disease.

Alzheimer's disease (AD) is an enormous healthcare challenge, and 50 million people are currently suffering from it. There are several pathophysiological mechanisms involved, but cholinesterase inhibitors remained the major target from the last 2-3 decades. Among four available therapeutics (donepezil, rivastigmine, galantamine, and memantine), three of them are cholinesterase inhibitors. Herein, we describe the role of acetylcholine sterase (AChE) and related hypothesis in AD along with the pharmacological and chemical aspects of the available cholinesterase inhibitors. This chapter discusses the development of several congeners and hybrids of available cholinesterase inhibitors along with their binding patterns in enzyme active sites.

Design and development of molecular hybrids of 2-pyridylpiperazine and 5-phenyl-1,3,4-oxadiazoles as potential multifunctional agents to treat Alzheimer's disease.

The diverse nature of Alzheimer's disease (AD) has prompted researchers to develop multi-functional agents. Herein, we have designed and synthesized molecular hybrids of 2-pyridylpiperazine and 5-phenyl-1,3,4-oxadiazoles. Biological activities of synthesized compounds suggested significant and balanced inhibitory potential against target enzymes. In particular, compound 49 containing 2,4-difluoro substitution at terminal phenyl ring considered as most potential lead with inhibition of acetylcholinesterase (hAChE, IC50 = 0.054 µM), butyrylcholinesterase (hBChE, IC50 = 0.787 µM) and beta-secretase-1 (hBACE-1, IC50 = 0.098 µM). The enzyme kinetics study of 49 against hAChE suggested a mixed type of inhibition (Ki = 0.030 µM). Also, 48 and 49 showed significant displacement of propidium iodide from the peripheral anionic site (PAS) of hAChE, excellent blood-brain barrier (BBB) permeability in parallel artificial membrane permeation assay (PAMPA), and neuroprotective ability against SH-SY5Y neuroblastoma cell lines. Further, 49 also exhibited anti-Aß aggregation activity in self- and AChE-induced thioflavin T assay, which was ascertained by morphological characterization by atomic force microscopy (AFM). Moreover, in vivo behavioral studies signified learning and memory improvement by compound 49 in scopolamine- and Aß-induced cognitive dysfunctions performed on Y-maze and Morris water maze. The ex vivo studies suggested decreased AChE activity and antioxidant potential of compound 49, with good oral absorption characteristics ascertained by pharmacokinetic studies.

Novel Molecular Hybrids of N-Benzylpiperidine and 1,3,4-Oxadiazole as Multitargeted Therapeutics to Treat Alzheimer's Disease.

Multitargeted hybrids of N-benzylpiperidine and substituted 5-phenyl-1,3,4-oxadiazoles were designed, synthesized, and evaluated against Alzheimer's disease (AD). Tested compounds exhibited moderate to excellent inhibition against human acetylcholinesterase (hAChE), butyrylcholinesterase (hBChE), and beta-secretase-1 (hBACE-1). The potential leads 6g and 10f exhibited balanced inhibitory profiles against all the targets, with a substantial displacement of propidium iodide from the peripheral anionic site of hAChE. Hybrids 6g and 10f also elicited favorable permeation across the blood-brain barrier and were devoid of neurotoxic liability toward SH-SY5Y neuroblastoma cells. Both leads remarkably disassembled Aß aggregation in thioflavin T-based self- and AChE-induced experiments. Compounds 6g and 10f ameliorated scopolamine-induced cognitive dysfunctions in the Y-maze test. The ex vivo studies of rat brain homogenates established the reduced AChE levels and antioxidant activity of both compounds. Compound 6g also elicited noteworthy improvement in Aß-induced cognitive dysfunctions in the Morris water maze test with downregulation in the expression of Aß and BACE-1 proteins corroborated by Western blot and immunohistochemical analysis. The pharmacokinetic study showed excellent oral absorption characteristics of compound 6g. The in silico molecular docking and dynamics simulation studies of lead compounds affirmed their consensual binding interactions with PAS-AChE and aspartate dyad of BACE-1.

Design, synthesis, and evaluation of novel N-(4-phenoxybenzyl)aniline derivatives targeting acetylcholinesterase, ß-amyloid aggregation and oxidative stress to treat Alzheimer's disease.

Novel hybrids N-(4-phenoxybenzyl)aniline were designed, synthesized, and evaluated for their potential AChE inhibitory activity along with antioxidant potential. The inhibitory potential (IC50) of synthesized analogs was evaluated against human cholinesterases (hAChE and hBChE) using Ellman's method. Among all the tested compounds, 42 with trimethoxybenzene substituent showed maximum hAChE inhibition with the competitive type of enzyme inhibition (IC50 = 1.32 µM; Ki = 0.879 µM). Further, parallel artificial membrane permeation assay (PAMPA-BBB) showed favorable BBB permeability by most of the synthesized compounds. Meanwhile, compound 42 also inhibited AChE-induced Aß aggregation (39.5-66.9%) in thioflavin T assay. The in vivo behavioral studies showed dose-dependent improvement in learning and memory by compound 42. The ex vivo studies also affirmed the significant AChE inhibition and antioxidant potential of compound 42 in brain homogenates.

Design and development of 1,3,4-oxadiazole derivatives as potential inhibitors of acetylcholinesterase to ameliorate scopolamine-induced cognitive dysfunctions.

The novel hybrids bearing 4-aminopyridine (4-AP) tethered with substituted 1,3,4-oxadiazole nucleus were designed, synthesized, and evaluated for their potential AChE inhibitory property along with significant antioxidant potential. The inhibitory potential (IC50) of synthesized analogs was evaluated against human cholinesterases (hAChE and hBChE) using Ellman's method. Among all the compounds, 9 with 4-hydroxyl substituent showed maximum hAChE inhibition with the non-competitive type of enzyme inhibition (IC50 = 1.098 µM; Ki = 0.960 µM). Further, parallel artificial membrane permeation assay (PAMPA-BBB) showed significant BBB permeability in most of the synthesized compounds. Meanwhile, compound 9 also inhibited AChE-induced Aß aggregation (38.2-65.9%) by thioflavin T assay. The in vivo behavioral studies showed dose-dependent improvement in learning and memory by compound 9. The ex vivo studies also affirmed the significant AChE inhibition and antioxidant potential of compound 9 in brain homogenates.

Design and development of multitarget-directed N-Benzylpiperidine analogs as potential candidates for the treatment of Alzheimer's disease.

The multitarget-directed strategy offers an effective and promising paradigm to treat the complex neurodegenerative disorder, such as Alzheimer's disease (AD). Herein, a series of N-benzylpiperidine analogs (17-31 and 32-46) were designed and synthesized as multi-functional inhibitors of acetylcholinesterase (AChE) and ß-secretase-1 (BACE-1) with moderate to excellent inhibitory activities. Among the tested inhibitors, 25, 26, 40, and 41 presented the most significant and balanced inhibition against both the targets. Compounds 40 and 41 exhibited high brain permeability in the PAMPA-BBB assay, significant displacement of propidium iodide from the peripheral anionic site (PAS) of AChE, and were devoid of neurotoxicity towards SH-SY5Y neuroblastoma cell lines up to the maximum tested concentration of 80 µM. Meanwhile, both these compounds inhibited self- and AChE-induced Aß aggregation in thioflavin T assay, which was also re-affirmed by morphological characterization of Aß aggregates using atomic force microscopy (AFM). Moreover, 40 and 41 ameliorated the scopolamine-induced cognitive impairment in elevated plus and Y-maze experiments. Ex vivo and biochemical analysis established the brain AChE inhibitory potential and antioxidant properties of these compounds. Further, improvement in Aß1-42-induced cognitive impairment was also observed by compound 41 in the Morris water maze experiment with significant oral absorption characteristics ascertained by the pharmacokinetic studies.