Cyclic acyl guanidines bearing carbamate moieties allow potent and dirigible cholinesterase inhibition of either acetyl- or butyrylcholinesterase

A series of cyclic acyl guanidine with carbamate moieties have been synthesized and evaluated in vitro for their AChE and BChE inhibitory activities. Structure−activity relationships identified compound 23 as a nanomolar and selective BChE inhibitor, while compound 32 exhibited nanomolar and selective AChE inhibition, selectivity depending on both the structure of the carbamate substituent as well as the position of guanidines-N substitution. The velocity of enzyme carbamoylation was analyzed and showed similar behavior to physostigmine. Phenolic compounds formed after carbamate transfer to the active site of cholinesterases showed additional neuroprotective properties on a hippocampal neuronal cell line (HT-22) after glutamate-induced intracellular reactive oxygen species generation.     

Alkynyl and β-ketophosphonates: Selective and potent butyrylcholinesterase inhibitors

A series of thirty-three alkynyl and β-ketophosphonates were evaluated for their in vitro acetyl- and butyryl-cholinesterase (AChE and BChE) inhibitory activities using Ellman’s spectrophotometric method. None of the examined compounds inhibited AChE activity at tested concentrations while twenty-nine of them showed significant and selective inhibition of BChE with IC₅₀ values between 38.60 µM and 0.04 µM. In addition, structure-activity relationships were discussed. The most effective inhibitors were the dibutyl o-methoxyphenyl alkynylphosphonate 3dc and dibutyl o-methoxyphenyl β-ketophosphonate 4dc. Activities of most potent compounds were also compared with a commercial organophosphorus compound. These results could inspire the design of new inhibitors with stronger activity against BChE.     

Novel N-benzylpyridinium moiety linked to arylisoxazole derivatives as selective butyrylcholinesterase inhibitors: Synthesis,biological evaluation,and docking study

A novel series of N-benzylpyridinium moiety linked to arylisoxazole ring were designed, synthesized, and evaluated for their in vitro acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) inhibitory activities. Synthesized compounds were classified into two series of 5a-i and 5j-q considering the position of positively charged nitrogen of pyridinium moiety (3- or 4- position, respectively) connected to isoxazole carboxamide group. Among the synthesized compounds, compound 5n from the second series of compounds possessing 2,4-dichloroaryl group connected to isoxazole ring was found to be the most potent AChE inhibitor (IC₅₀ = 5.96 µM) and compound 5j also from the same series of compounds containing phenyl group connected to isoxazole ring demonstrated the most promising inhibitory activity against BChE (IC₅₀ = 0.32 µM). Also, kinetic study demonstrated competitive inhibition mode for both AChE and BChE inhibitory activity. Docking study was also performed for those compounds and desired interactions with those active site amino acid residues were confirmed through hydrogen bonding as well as π-π and π-anion interactions. In addition, the most potent compounds were tested against BACE1 and their neuroprotectivity on Aβ-treated neurotoxicity in PC12 cells which depicted negligible activity. It should be noted that most of the synthesized compounds from both categories 5a-i and 5j-q showed a significant selectivity toward BChE. However, series 5j-q were more active toward AChE than series 5a-i.     

3,4-Dihydroquinazoline derivatives inhibit the activities of cholinesterase enzymes

A series of 3,4-dihydroquinazoline derivatives consisting of the selected compounds from our chemical library on the diversity basis and the new synthetic compounds were in vitro tested for their inhibitory activities for both acetylcholinesterase (AChE, from electric eel) and butyrylcholinesterase (BChE, from equine serum) enzymes. It was discovered that most of the compounds displayed weak AChE and strong BuChE inhibitory activities. In particular, compound 8b and 8d were the most active compounds in the series against BChE with IC₅₀ values of 45 nM and 62 nM, as well as 146- and 161-fold higher affinity to BChE, respectively. To understand the excellent activity of these compounds, molecular docking simulations were performed to get better insights into the mechanism of binding of 3,4-dihydroquinazoline derivatives. As expected, compound 8b and 8d bind to both catalytic anionic site (CAS) and peripheral site (PS) of BChE with better interaction energy values than AChE, in agreement with our experimental data. Furthermore, the non-competitive/mixed-type inhibitions of both compounds further confirmed their dual binding nature in kinetic studies.     

Novel multi-targeted agents for Alzheimer's disease: Synthesis,biological evaluation,and molecular modeling of novel 2-[4-(4-substitutedpiperazin-1-yl)phenyl]benzimidazoles

The present study describes the synthesis, pharmacological evaluation (BChE/AChE inhibition, Aβ antiaggregation, and neuroprotective effects), and molecular modeling studies of novel 2-[4-(4-substitutedpiperazin-1-yl)phenyl]benzimidazole derivatives. The alkyl-substituted derivatives exhibited selective inhibition on BChE with varying efficiency. Compounds 3b and 3d were found to be the most potent inhibitors of BChE with IC₅₀ values of 5.18 and 5.22 μM, respectively. The kinetic studies revealed that 3b is a partial non-competitive BChE inhibitor. Molecular modeling studies also showed that the alkyl-substituted derivatives were able to reach the catalytic anionic site of the BChE. The compounds with an inhibitory effect on BChE were subsequently screened for their Aβ antiaggregating and neuroprotective activities. Compounds 3a and 3b exerted a potential neuroprotective effect against H₂O₂ and Aβ-induced cytotoxicity in SH-SY5Y cells. Collectively, 3b was found as the most promising compound for the development of multi-target directed ligands against Alzheimer’s disease.     

Design,synthesis and evaluation of novel 7-aminoalkyl-substituted flavonoid derivatives with improved cholinesterase inhibitory activities

A novel series of 7-aminoalkyl-substituted flavonoid derivatives 5a–5r were designed, synthesized and evaluated as potential cholinesterase inhibitors. The results showed that most of the synthesized compounds exhibited potent acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) inhibitory activities at the micromolar range. Compound 2-(naphthalen-1-yl)-7-(8-(pyrrolidin-1-yl)octyloxy)-4H-chromen-4-one (5q) showed the best inhibitory activity (IC₅₀, 0.64 μM for AChE and 0.42 μM for BChE) which were better than our previously reported compounds and the commercially available cholinergic agent Rivastigmine. The results from a Lineweaver–Burk plot indicated a mixed-type inhibition for compound 5q with AChE and BChE. Furthermore, molecular modeling study showed that 5q targeted both the catalytic active site (CAS) and the peripheral anionic site (PAS) of AChE. Besides, these compounds (5a–5r) did not affect PC12 and HepG2 cell viability at the concentration of 10 μM. Consequently, these flavonoid derivatives should be further investigated as multipotent agents for the treatment of Alzheimer’s disease.     

The development of 2-acetylphenol-donepezil hybrids as multifunctional agents for the treatment of Alzheimer’s disease

A series of 2-acetylphenol-donepezil hybrids was designed and synthesized based on multi-target-directed ligands strategy. The biological activities were evaluated by AChE/BChE inhibition and MAO-A/MAO-B inhibition. The results revealed that the tertiary amines and methylene chain length significantly affected the eeAChE inhibitory potency, in particular, compound TM-14 showed the best eeAChE inhibitory activity with IC₅₀ value of 2.9 μM, in addition, both kinetic analysis of AChE inhibition and docking study displayed that TM-14 could simultaneously bind to the catalytic active site and peripheral anionic site of AChE. Moreover, compound TM-14 was a selective metal chelator and could form 1:1 TM-14-Cu²⁺ complex. The structure-active-relationship also indicated that the O-alkylamine fragment remarkably decreased hMAO-B inhibitory activity, compound TM-2 exhibited potent hMAO-B inhibitory activity (IC₅₀ = 6.8 μM), which was supported by the molecular docking study. More interestingly, compounds TM-14 and TM-2 could cross the blood-brain barrier in vitro. Therefore, the structure-active-relationship of 2-acetylphenol-donepezil hybrids could encourage the development of multifunction agents with selective AChE inhibition or selective MAO-B inhibition for the treatment of Alzheimer’s disease.     

Modification of Bischler-Möhlau indole derivatives through palladium catalyzed Suzuki reaction as effective cholinesterase inhibitors,their kinetic and molecular docking studies

Due to the immense importance of aryl indole nucleus, herein we report the palladium-catalyzed arylation of N-substituted 2-aryl indole utilizing Suzuki-Miyaura cross coupling methodology. The biological screening for cholinesterase inhibition of the resulted biaryl indole moieties was carried out to evaluate their pharmacological potential, expecting to involve the development of new therapeutics for various inflammatory, cardiovascular, gastrointestinal and neurological diseases. This research work also involved the use of utilization of microwave-assisted organic synthesis (MAOS) for the synthesis of Bischler-Möhlau indole which is further biarylated via palladium-catalyzed cross coupling reaction. All the synthetic compounds (3a-n) were tested for cholinesterase inhibition and exhibited high level of AChE inhibitory activities. Interestingly, compounds 3m and 3n were found to be dual inhibitors, however, remaining compound exhibited no inhibitory activity against BChE. The biological potential of the resulted compounds was explained on the basis of molecular docking studies, performed against AChE and BChE, exploring the probable binding modes of most potent inhibitors.     

Molecular-docking-guided design and synthesis of new IAA-tacrine hybrids as multifunctional AChE/BChE inhibitors

A series of new indole-3-acetic acid (IAA)-tacrine hybrids as dual acetylcholinesterase (AChE)/butyrylcholinesterase (BChE) inhibitors were designed and prepared based on the molecular docking mode of AChE with an IAA derivative (1a), a moderate AChE inhibitor identified by screening our compound library for anti-Alzheimer’s disease (AD) drug leads. The enzyme assay results revealed that some hybrids, e.g. 5d and 5e, displayed potent dual in vitro inhibitory activities against AChE/BChE with IC₅₀ values in low nanomolar range. Molecular modeling studies in tandem with kinetic analysis suggest that these hybrids target both catalytic active site and peripheral anionic site of cholinesterase (ChE). Molecular dynamic simulations and Molecular Mechanics/Poisson-Boltzmann Surface Area (MM-PBSA) calculations indicate that 5e has more potent binding affinity than hit 1a, which may explain the stronger inhibitory effect of 5e on AChE. Furthermore, their predicted pharmacokinetic properties and in vitro influences on mouse brain neural network electrical activity were discussed. Taken together, compound 5e can be highlighted as a lead compound worthy of further optimization for designing new anti-AD drugs.     

Design,synthesis and biological evaluation of benzofuran appended benzothiazepine derivatives as inhibitors of butyrylcholinesterase and antimicrobial agents

A series of bezofuran appended 1,5-benzothiazepine compounds 7a–v was designed, synthesized and evaluated as cholinesterase inhibitors. The biological assay experiments showed that most of the compounds displayed a clearly selective inhibition for butyrylcholinesterase (BChE), while a weak or no effect towards acetylcholinesterase (AChE) was detected. All analogs exhibited varied BChE inhibitory activity with IC₅₀ value ranging between 1.0?±?0.01 and 72?±?2.8?μM when compared with the standard donepezil (IC₅₀, 2.63?±?0.28?μM). Among the synthesized derivatives, compounds 7l, 7m and 7k exhibited the highest BChE inhibition with IC₅₀ values of 1.0, 1.0 and 1.8?μM, respectively. The results from a Lineweaver-Burk plot indicated a mixed-type inhibition for compound 7l with BChE. In addition, docking studies confirmed the results obtained through in vitro experiments and showed that most potent compounds bind to both the catalytic anionic site (CAS) and peripheral anionic site (PAS) of BChE active site. The synthesized compounds were also evaluated for their in vitro antibacterial and antifungal activities. The results indicated that the compounds possessed a broad spectrum of activity against the tested microorganisms and showed high activity against both gram positive and gram negative bacteria and fungi.     

Pyridine sulfonamide as a small key organic molecule for the potential treatment of type-II diabetes mellitus and Alzheimer’s disease: In vitro studies against yeast α-glucosidase,acetylcholinesterase and butyrylcholinesterase

This paper presents the efficient high yield synthesis of novel pyridine 2,4,6-tricarbohydrazide derivatives (4a–4i) along with their α-glucosidase, acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) inhibition activities. The enzymes inhibition results showed the potential of synthesized compounds in controlling both type-II diabetes mellitus and Alzheimer’s disease. In vitro biological investigations revealed that most of compounds were more active against yeast α-glucosidase than the reference compound acarbose (IC₅₀ 38.25 ± 0.12 μM). Among the tested series the compound 4c bearing 4-flouro benzyl group was noted to be the most active (IC₅₀ 25.6 ± 0.2 μM) against α-glucosidase, and it displayed weak inhibition activities against AChE and BChE. Compound 4a exhibited the most desired results against all three enzymes, as it was significantly active against all the three enzymes; α-glucosidase (IC₅₀ 32.2 ± 0.3 μM), AChE (IC₅₀ 50.2 ± 0.8 μM) and BChE (IC₅₀ 43.8 ± 0.8 μM). Due to the most favorable activity of 4a against the tested enzymes, for molecular modeling studies this compound was selected to investigate its pattern of interaction with α-glucosidase and AChE targets.     

Cholinesterase inhibitory activity versus aromatic core multiplicity: A facile green synthesis and molecular docking study of novel piperidone embedded thiazolopyrimidines

Novel thiazolopyrimidine derivatives have been synthesized via microwave assisted, domino cascade methodology in ionic liquid and evaluated in vitro for their acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) inhibitory activities. Among the newly synthesized compounds 6d, 6a, 6e and 6b displayed higher AChE inhibitory activity than standard drug, galanthamine, with IC₅₀ values of 0.53, 1.47, 1.62 and 2.05 μM, respectively. Interestingly, all the compounds except for 6m–r and 6x displayed higher BChE inhibitory potentials than galanthamine with IC₅₀ values ranging from 1.09 to 18.56 μM. Molecular docking simulations for 6d possessing the most potent AChE and BChE inhibitory activities, disclosed its binding interactions at the active site gorge of AChE and BChE enzymes.     

Synthesis,biological evaluation and docking studies of 2,3-dihydroquinazolin-4(1H)-one derivatives as inhibitors of cholinesterases

In search of potent inhibitors of cholinesterases, we have synthesized and evaluate a number of 2,3-dihydroquinazolin-4(1H)-one derivatives. The synthetic approach provided an efficient synthesis of the target molecules with excellent yield. All the tested compounds showed activity against both the enzymes in micromolar range. In many case, the inhibition of both enzymes are higher than or comparable to the standard drug galatamine. With the selectivity index of 2.3 for AChE, compound 5f can be considered as a potential lead compound with a feature of dual AChE/BChE inhibition with IC₅₀ = 1.6 ± 0.10 μM (AChE) and 3.7 ± 0.18 μM (BChE). Binding modes of the synthesized compounds were explored by using GOLD (Genetic Optimization for Ligand Docking) suit v5.4.1. The computed binding modes of these compounds in the active site of AChE and BChE provide an insight into the mechanism of inhibition of these two enzyme.     

Synthesis and cholinesterase inhibitory activity study of new piperidone grafted spiropyrrolidines

Alzheimer’s disease (AD) is a prevalent neurodegenerative disorder, which affected 35 million people in the world. The most practiced approach to improve the life expectancy of AD patients is to increase acetylcholine neurotransmitter level at cholinergic synapses by inhibition of cholinesterase enzymes. A series of unreported piperidone grafted spiropyrrolidines 8(a-p) were synthesized and evaluated in vitro for their acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) inhibitory activities. Therein, compounds 8h and 8l displayed more potent AChE enzyme inhibition than standard drug with IC₅₀ values of 1.88 and 1.37 µM, respectively. Molecular docking simulations for 8l possessing the most potent AChE inhibitory activities, disclosed its interesting binding templates to the active site channel of AChE enzymes. These compounds are remarkable AChE inhibitors and have potential as AD drugs.     

Investigation of biological activities of various 1,2,3-triazole compounds: Their effects on cholinesterase enzymes,determination of antioxidant capacity and antimicrobial activity

1,2,3-triazoles are pharmaceutically significant compounds that have attracted recent interest from medicinal chemists because of their important biological activities. Addressed herein, some 1,2,3-triazoles were synthesized to investigate the inhibitory activities against acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) enzymes, antioxidant capacity, and antimicrobial effect. The antioxidant profile of 1,2,3-triazoles determined by varied bioanalytical antioxidant methods, including 2,2′-azino-bis (3-ethylbenzthiazoline-6-sulfonic acid) (ABTS^.+), 1,1-diphenyl-2-picrylhydrazil (DPPH·), cupric ion (Cu²⁺) and ferric ion (Fe³⁺) ascorbic acid, butylated hydroxyanisole (BHA), and butylated hydroxytoluene (BHT) were used as the standard compounds. In addition, the antibacterial and antifungal activities of these compounds were investigated against seven bacteria and three fungal species using the hollow agar method. As a result of these studies, it was determined that compound 4 showed the best antimicrobial activity and antioxidant activity close to the standards. Inhibitory effects and kinetic studies of these molecules on cholinesterase enzymes were performed. According to the results obtained, compound 4 showed stronger AChE inhibition and compound 3 stronger BChE inhibition compared to other compounds. In kinetic studies, it was found that AChE showed noncompetitive inhibition by compound 4, and BChE showed competitive inhibition by compound 3.     

Design, synthesis and evaluation of flavonoid derivatives as potent AChE inhibitors

A new series of flavonoid derivatives have been designed, synthesized and evaluated as potent AChE inhibitors. Most of them showed more potent inhibitory activities to AChE than rivastigmine. The most potent inhibitor isoflavone derivative 10d inhibit AChE with a IC₅₀ of 4 nM and showed high BChE/AChE inhibition ratio (4575-fold), superior to donepezil (IC₅₀ = 12 nM, 389-fold). Molecular docking studies were also performed to explore the detailed interaction with AChE.     

Juliflorine: A potent natural peripheral anionic-site-binding inhibitor of acetylcholinesterase with calcium-channel blocking potential, a leading candidate for Alzheimer’s disease therapy

The alkaloid juliflorine (1) from Prosopis juliflora inhibited acetylcholinesterase (AChE, EC 3.1.1.7) and butyrylcholinesterase (BChE, EC 3.1.1.8) enzymes in a concentration-dependent fashion with IC₅₀ values 0.42 and 0.12 μM, respectively. Lineweaver-Burk as well as Dixon plots and their secondary replots indicated that the nature of inhibition was purely of non-competitive type with K_i values 0.4 and 0.1 μM, against AChE and BChE, respectively. By molecular docking studies compound 1 was found to be ideally spaced inside the aromatic gorge of AChE with rings A/B remaining at the top and rings C/D penetrating deep into the gorge, that might be due to the greater hydrophobicity of rings C/D as compared to rings A/B, allowing their simultaneous interaction with the peripheral anionic and quaternary ammonium-binding sites. The 1-AChE complex was found to be stabilized by hydrophobic contacts, hydrogen bonding, and π-π stacking between the compound 1 and amino acid residues of the aromatic gorge of AChE. Amino acid residues Tyr70, Asp72, Tyr121, Trp279, and Tyr334 of the peripheral anionic site (PAS) of AChE were found to be exclusively involved in the hydrophobic contacts with compound 1 that might be responsible for the competitive mode of inhibition. Compound 1 also showed dose-dependent (30-500 μg/mL) spasmolytic and Ca²⁺-channel blocking activities in isolated rabbit jejunum preparations. The cholinesterase inhibitory potential along with calcium-channel blocking activity of compound 1 and safe profile in human neutrophils viable assay could make it a possible drug candidate for Alzheimer’s disease.     

Synthesis and discovery of highly functionalized mono- and bis-spiro-pyrrolidines as potent cholinesterase enzyme inhibitors

Novel mono and bis spiropyrrolidine derivatives were synthesized via an efficient ionic liquid mediated, 1,3-dipolar cycloaddition methodology and evaluated in vitro for their AChE and BChE inhibitory activities in search for potent cholinesterase enzyme inhibitors. Most of the synthesized compounds displayed remarkable AChE inhibitory activities with IC₅₀ values ranging from 1.68 to 21.85 μM, wherein compounds 8d and 8j were found to be most active inhibitors against AChE and BChE with IC₅₀ values of 1.68 and 2.75 μM, respectively. Molecular modeling simulation on Torpedo californica AChE and human BChE receptors, showed good correlation between IC₅₀ values and binding interaction template of the most active inhibitors docked into the active site of their relevant enzymes.     

Synthesis and biological evaluation of pyrano[4,3-b][1]benzopyranone derivatives as monoamine oxidase and cholinesterase inhibitors

A series of eighteen pyrano[4,3-b][1]benzopyranone derivatives (1a-9b) were synthesized, and structure-activity relationships of their monoamine oxidase (MAO) A and B, acetylcholinesterase (AChE), and butyrylcholinesterase (BChE) inhibitory activities were evaluated. Most of the synthesized compounds exhibited weak inhibitory activity toward MAO-A, whereas compounds 2a, 2b, 4a, 4b, 5a, 5b, 6a, 6b, 8a and 8b showed potent inhibitory activities toward MAO-B. Intriguingly, compounds 5a, 5b, and 8a showed inhibitory activities comparable to pargylin, used as a positive control for MAO-B. Substitution of butoxy at the C3 position or of chlorine at the C8 position of pyrano[4,3-b][1]benzopyranone increased the inhibitory activity of the compound toward MAO-B. The results of a molecular docking study supported this structural effect. Most of the compounds exhibited no or slight inhibitory activity toward AChE and BChE, with exo type compounds bearing a butoxy group, such as compounds 2b, 5b and 8b, showing weak but distinct inhibitory activities toward BChE. This report is the first to identify pyrano[4,3-b][1]benzopyranone derivatives as potent and selective MAO-B inhibitors. 3-Butoxy-8-chloro-pyrano[4,3-b][1]benzopyranone (5b) may be useful as a lead compound for the development of MAO-B inhibitors.     

1,2,3,4,6-penta-O-galloyl-β-d-glucose: A cholinesterase inhibitor from Terminalia chebula

The search for a novel pharmacotherapy from medicinal plants for neurodegenerative disorders has significantly advanced. Therefore, the present study was performed to evaluate the anticholinesterase activities of one hundred medicinal plants in Korea, where Terminalia chebula (T. chebula) fruits showed significant acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) inhibitions. Further bioassay monitored phytochemical exploration led to the isolation of 1,2,3,4,6-penta-O-galloyl-β-d-glucose (compound 1), which showed significant AChE and BChE inhibitory effects with IC₅₀ values of 29.9 ± 0.3 µM and 27.6 ± 0.2 µM, respectively. The inhibitory effect of compound 1 towards acetylcholinesterase was also evaluated using TLC and compared with tacrine as the positive control; the positive effect was confirmed. Furthermore, compound 1 also displayed strong antioxidant activity by the FRAP assay (IC₅₀ = 4.6 ± 0.2 µM). In conclusion, compound 1 may prove to be a potential natural anti-Alzheimer source based on noteworthy AChE and BChE inhibitions, and strong antioxidant activity.