Potent Butyrylcholinesterase Inhibitors Research Articles

Synthesis and Characterization of Esterified Fmoc‐Amino Esters as Potential Butyrylcholinesterase Inhibitors

Neurodegenerative diseases such as Alzheimer's disease (AD) is the sixth leading cause of death in the United States and affects 5.7 million Americans. While cures for this disease have not yet been discovered, several pharmaceuticals are available to alleviate symptoms. These compounds typically target the enzymes acetylcholinesterase (AChE) and butyrylcholinesterase (BChE). Specifically, for individuals with AD it has been found that while AChE activity is slightly decreased or unaffected, BChE activity is increased. The increased BChE activity leads to a depletion of the neurotransmitter acetylcholine, and this is implicated in the progression of dementia. Thus, inhibitors of BChE are sought in AD treatment. We previously found Fluorenylmethyloxycarbonyl (Fmoc)‐amino acids selectively inhibit BChE, leading to a potential new class of cholinesterase inhibitors. While the role of the amino acid side chain was explored, the effects of modifying the carboxylate group were not investigated. Specifically, the enzyme binds the cationic substrate acetylcholine, but the Fmoc‐amino acids are anionic. We postulated Fmoc‐amino acid esters may be more potent inhibitors, as the ester ablates the negative charge. In addition, the ester allows incorporation of substituents that increase van der Waals interactions that may interact favorably with the enzyme. To test this model, a series of Fmoc‐amino acids were esterified using an alcohol and EEDQ (N‐Ethoxycarbonyl‐2‐ethoxy‐1,2‐dihydroquinoline), purified by chromatography, and characterized by NMR and HPLC. The solubility and inhibition properties for the Fmoc‐containing esters were evaluated using UV‐Vis spectroscopy. Kinetic studies suggest the Fmoc‐Leu‐esters are more potent inhibitors compared to the Fmoc‐Leu‐O− but are limited by solubility. We are now investigating additional Fmoc‐amino acid esters bearing cationic groups to enhance solubility such as lysine, and our initial results suggest the lysine‐based compounds are potent BChE inhibitors. Overall, the results may guide the design of new Fmoc‐containing compounds that specifically and effectively inhibit BChE.Support or Funding InformationThis project is supported by the National Institute of General Medical Sciences of the National Institutes of Health under Award Numbers R25GM071638, UL1GM118979, TL4GM118980, RL5GM118978, and T34 GM008074.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Design, synthesis, in vivo and in vitro studies of 1,2,3,4-tetrahydro-9H-carbazole derivatives, highly selective and potent butyrylcholinesterase inhibitors.

Inhibition of butyrylcholinesterase (BChE) might be a useful therapeutic target for Alzheimer's disease (AD). A new series of 1,2,3,4-tetrahydro-9H-carbazole derivatives were designed synthesized and evaluated as BChE inhibitors. While all of the derivatives have shown for AChE IC50 values below the detectable limit (> 100µM), they were selective potent BChE inhibitors. 1-(2-(6-fluoro-1,2,3,4-tetrahydro-9H-carbazole-9-yl)ethyl)piperidin-1-ium chloride (15g) had the most potent anti-BChE activity (IC50 value = 0.11μM), the highest BChE selectivity and mixed-type inhibition. Pharmacokinetic properties were accordant to Lipinski rule and compound 15g demonstrated neuroprotective and inhibition of β-secretase (BACE1) activities. Furthermore, in vivo study of compound 15g in Morris water maze task has confirmed memory improvement in scopolamine-induced impairment. All results suggest that new sets of potent selective inhibitors of BChE have a therapeutic potential for the treatment of AD. A new series of 1,2,3,4-tetrahydro-9H-carbazole derivatives were designed synthesized and evaluated as BChE inhibitors. While all of the derivatives have shown for AChE IC50 values below the detectable limit, they were selective potent BChE inhibitors. Compound 15g had the most potent anti-BChE activity. All results suggest that new sets of potent selective inhibitors of BChE have a therapeutic potential for the treatment of AD.

QSAR, Docking and Molecular Dynamics Studies on the Piperidone-grafted Mono- and Bis-spiro-oxindole-hexahydropyrrolizines as Potent Butyrylcholinesterase Inhibitors

ABSTRACT: Quantitative structure-activity relationship (QSAR) study on the piperidone-grafted mono- and bis-spirooxindole-hexahydropyrrolizines as potent butyrylcholinestrase (BuChE) inhibitors were carried out using statistical methods, molecular dynamics and molecular docking simulation. QSAR methodologies, including classification and regression tree (CART), multiple linear regression (MLR), principal component analysis (PCA) and principal component regression analysis (PCRA). Three descriptors in three classes: 3D-Morse, WHIM and GETAWAY descriptors were selected by SPSS software and then applied in the final tree structure to describe the inhibitory activities. Docking simulations were carried out using AutoDock Vina softwares for all inhibitors. Docking results showed that the studied BuChE inhibitors have two commons binding modes. Molecular dynamics results obtained by Gromacs showed that the more potent inhibitor has more interaction with the enzyme and higher effect on the enzyme structure.

Computational and experimental studies on the interaction between butyrylcholinesterase and fluoxetine: implications in health and disease

Butyrylcholinesterase (BChE) is a serine esterase that plays a role in the detoxification of natural as well as synthetic ester-bond-containing compounds. Alterations in BChE activity are associated with a number of diseases. Cholinergic system abnormalities in particular are correlated with the formation of senile plaques in Alzheimer’s disease (AD), and administration of cholinesterase inhibitors is a common therapeutic approach used to treat AD.Here, our aim was to study the interaction between BChE and fluoxetine.Molecular docking simulations revealed that fluoxetine penetrated deep into the active-site gorge of BChE and that it was engaged in stabilizing noncovalent interactions with multiple subsites. In substrate kinetic studies, the Vm, Km, kcat and kcat/Km values were found to be 20.59 ± 0.36 U mg−1 protein, 194 ± 14 µM, 1.3 × 108 s−1 and 6.7 × 105 µM−1s−1, respectively. Based on inhibitory studies, fluoxetine appeared to inhibit BChE competitively, with an IC50 value of 104 µM and a Ki value of 36.3 ± 4.7 µM.Overall, both the low Ki value and the high number of BChE–fluoxetine interactions suggest that fluoxetine is a potent inhibitor of BChE, although in vivo mechanisms for the direct effects of BChE inhibition on various pathologies remain to be further investigated.

Design, synthesis and cholinesterase inhibitory activity of α-mangostin derivatives

α-mangostin, a polyphenol xanthone derivative, was mainly isolated from pericarps of the mangosteen fruit (Garcinia mangostana L.). In present investigation, a series of derivatives were designed, synthesised and evaluated in vitro for their inhibitory activity of acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE). Among the synthesised xanthones, compounds 1, 9, 13 and 16 showed AChE selective inhibitory activity, 15 was a BuChE selective inhibitor while 2, 3, 5, 6, 7, 12 and 14 were dual inhibitors. The most potent inhibitor of AChE was 16 while 5 was the most potent inhibitor of BuChE with IC50 values of 5.26 μM and 7.55 μM respectively.

Design and evaluation of selective butyrylcholinesterase inhibitors based on Cinchona alkaloid scaffold.

This paper describes the synthesis and anticholinesterase potency of Cinchona-based alkaloids; ten quaternary derivatives of cinchonines and their corresponding pseudo-enantiomeric cinchonidines. The quaternization of quinuclidine moiety of each compound was carried out with groups diverse in their size: methyl, benzyl and differently meta- and para-substituted benzyl groups. All of the prepared compounds reversibly inhibited human butyrylcholinesterase and acetylcholinesterase with Ki constants within nanomolar to micromolar range. Five cinchonidine derivatives displayed 95–510 times higher inhibition selectivity to butyrylcholinesterase over acetylcholinesterase and four were potent butyrylcholinesterase inhibitors with Ki constants up to 100 nM, of which N-para-bromobenzyl cinchonidinium bromide can be considered a lead for further modifications and optimizations for possible use in the treatment of neurodegenerative diseases.

Novel cinnamic acid-tryptamine hybrids as potent butyrylcholinesterase inhibitors: Synthesis, biological evaluation, and docking study.

A novel series of cinnamic acid-tryptamine hybrids was designed, synthesized, and evaluated as cholinesterase inhibitors. Anticholinesterase assays showed that all of the synthesized compounds displayed a clearly selective inhibition of butyrylcholinesterase (BChE), but only a moderate inhibitory effect toward acetylcholinesterase (AChE) was detected. Among these cinnamic acid-tryptamine hybrids, compound 7d was found to be the most potent inhibitor of BChE with an IC50 value of 0.55 ± 0.04 μM. This compound showed a 14-fold higher inhibitory potency than the standard drug donepezil (IC50 = 7.79 ± 0.81 μM) and inhibited BChE through a mixed-type inhibition mode. Moreover, a docking study revealed that compound 7d binds to both the catalytic anionic site (CAS) and the peripheral anionic site (PAS) of BChE. Also, compound 7d was evaluated against β-secretase, which exhibited low activity (inhibition percentage: 38%).

Synthesis and cholinesterase inhibitory activity of new 2-benzofuran carboxamide-benzylpyridinum salts

A series of benzofuran-2-carboxamide-N-benzyl pyridinium halide derivatives (6a-o) are synthesized as new cholinesterase inhibitors. The synthetic pathway involves the reaction of salicylaldehyde derivatives and ethyl bromoacetate, followed by hydrolysis and amidation with 3- and 4-picolyl amine. Subsequently, N-((pyridin-4-yl) methyl) benzofuran-2-carboxamide and substituted N-((pyridin-3-yl) methyl) benzofuran-2-carboxamides reacts with benzyl halides to afford target compounds (6a-o). The chemical structures of all derivatives were confirmed by spectroscopic methods. The studies reveal that some of the synthesized compounds are potent butyrylcholinesterase inhibitors with IC50 values in the range of 0.054–2.7 µM. In addition, good inhibitory effects on Aβ self-aggregation are observed for 6h and 6k (33.1 and 46.4% at 100 µM, respectively).

Novel tetrahydrocarbazole benzyl pyridine hybrids as potent and selective butryl cholinesterase inhibitors with neuroprotective and β-secretase inhibition activities

Butyrylcholinesterase (BuChE) inhibitors have become interesting target for treatment of Alzheimer's disease (AD). A series of dual binding site BuChE inhibitors were designed and synthesized based on 2,3,4,9-tetrahydro-1H-carbazole attached benzyl pyridine moieties. In-vitro assay revealed that all of the designed compounds were selective and potent BuChE inhibitors. The most potent BuChE inhibitor was compound 6i (IC50 = 0.088 ± 0.0009 μM) with the mixed-type inhibition. Docking study revealed that 6i is a dual binding site BuChE inhibitor. Also, Pharmacokinetic properties for 6i were accurate to Lipinski's rule. In addition, compound 6i demonstrated neuroprotective and β-secretase (BACE1) inhibition activities. This compound could also inhibit AChE-induced and self-induced Aβ peptide aggregation at concentration of 100 μM and 10 μM respectively. Generally, the results are presented as new potent selective BuChE inhibitors with a therapeutic potential for the treatment of AD.

Synthesis, Anticholinesterase, Antioxidant, and Anti‐Aflatoxigenic Activity of Novel Coumarin Carbamate Derivatives

AbstractNew coumarin derivatives with the carbamate moiety were synthesized and their inhibitory effects on acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) were evaluated. 4‐methyl‐2‐oxo‐2H‐chromen‐7‐yl cycloheptylcarbamate (4 h) showed the strongest inhibition against AChE with IC50 values of 2.30 μM, and 2‐oxo‐2H‐chromen‐7‐yl‐(cyclohexylmethyl)carbamate (4 c) and 4‐methyl‐2‐oxo‐2H‐chromen‐7‐yl‐(cyclohexylmethyl)carbamate (4 g) were found to be the most potent BuChE inhibitors with IC50 value of 0.003 μM and 0.004 μM, respectively. Moreover antioxidant, anti‐aflatoxigenic activities, protective effects against aflatoxin‐B1 (AFB1) in H4IIE−C3 cells and effects on glutathione s‐transferase of the synthesized compounds were investigated. The synthesized coumarin carbamates inhibited AFB1 in H4IIE−C3 cells. Western blot analyses confirmed that GSTα protein was induced in cells treated with coumarin carbamates and AFB1. These results showed that the synthesized coumarin carbamates possess a potent protective effect against AFB1.

Multidirectional investigations on different parts of Allium scorodoprasum L. subsp. rotundum (L.) Stearn: Phenolic components, in vitro biological, and in silico propensities

Allium species have been widely used for culinary and medicinal purposes. This study attempts for the first time to investigate into the enzyme inhibitory potential of different plant parts of Allium scorodoprasum L. subsp. rotundum (L.) Stearn, also known as wild garlic or leek in Turkey. The antioxidant and enzyme inhibitory potential of the flower, stem, and bulb extracts of A. scorodoprasum were assessed using in vitro bio-assays. The phenolic composition of the different plant parts was also established. The flower extract, having high phenolic content (27.69 mg GAEg extract), showed potent antioxidant activity as a metal chelating agent (22.27 mg EDTAE/g extract), radical scavenger (34.83 and 66.02 mg trolox equivalent (TE)/g extract, for 2,2-diphenyl-1-picrylhydrazyl and 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) assays, respectively) and reducing agent (90.53 mg TE/g extract, for the cupric reducing antioxidant capacity assay). Besides, the flower extract was a potent inhibitor of butyrylcholinesterase (3.16 mg galantamine equivalent (GALAE)/g extract) and tyrosinase (55.21 mg kojic acid equivalent/g extract). The flower extract was rich in rosmarinic acid. In silico studies revealed that rosmarinic acid established several hydrogen bonds and π–π interactions in the enzymatic cavity of butyrylcholinesterase. On the other hand, the stem extract of A. scorodoprasum showed inhibitory action against acetylcholinesterase (2.17 mg GALAE/g extract) and α-amylase (0.55 mmol acarbose equivalent/g extract). Interestingly, we noted that the bulb extract of A. scorodoprasum, inferior in phenolic compounds, showed the least activity. These results suggest that the different plant parts of A. scorodoprasum possessed different biological activities and might be used as a medicinal food plants for specific therapeutic applications.

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.

Chameleon-like behavior of indolylpiperidines in complex with cholinesterases targets: Potent butyrylcholinesterase inhibitors

Alzheimer's disease (AD) is the most common form of dementia worldwide with an increasing prevalence for the next years. The multifactorial nature of AD precludes the design of new drugs directed to a single target being probably one of the reasons for recent failures. Therefore, dual binding site acetylcholinesterase (AChE) inhibitors have been revealed as cognitive enhancers and β-amyloid modulators offering an alternative in AD therapy field. Based on the dual ligands NP61 and donepezil, the present study reports the synthesis of a series of indolylpiperidines hybrids to optimize the NP61 structure preserving the indole nucleus, but replacing the tacrine moiety of NP61 by benzyl piperidine core found in donepezil. Surprisingly, this new family of indolylpiperidines derivatives showed very potent and selective hBuChE inhibition. Further studies of NMR and molecular dynamics have showed the capacity of these hybrid molecules to change their bioactive conformation depending on the binding site, being capable to inhibit with different shapes BuChE and residually AChE.

HPLC-DAD finger printing, antioxidant, cholinesterase, and \u03b1-glucosidase inhibitory potentials of a novel plant Olax nana

BackgroundThe medicinal importance of a novel plant Olax nana Wall. ex Benth. (family: Olacaceae) was revealed for the first time via HPLC-DAD finger printing, qualitative phytochemical analysis, antioxidant, cholinesterase, and α-glucosidase inhibitory assays.MethodsThe crude methanolic extract of O. nana (ON-Cr) was subjected to qualitative phytochemical analysis and HPLC-DAD finger printing. The antioxidant potential of ON-Cr was assessed via 1,1-diphenyl,2-picrylhydrazyl (DPPH), 2,2-azinobis[3-ethylbenzthiazoline]-6-sulfonic acid (ABTS) and hydrogen peroxide (H2O2) free radical scavenging assays. Furthermore, acetylcholinesterase (AChE) & butyrylcholinesterase (BChE) inhibitory activities were performed using Ellman’s assay, while α- glucosidase inhibitory assay was carried out using a standard protocol.ResultsThe qualitative phytochemical analysis of ON-Cr revealed the presence of secondary metabolites like alkaloids, flavonoids, tannins, sterols, saponins and terpenoids. The HPLC-DAD finger printing revealed the presence of 40 potential compounds in ON-Cr. Considerable anti-radical activities was revealed by ON-Cr in the DPPH, ABTS and H2O2 free radical scavenging assays with IC50 values of 71.46, 72.55 and 92.33 μg/mL, respectively. Furthermore, ON-Cr showed potent AChE and BChE inhibitory potentials as indicated by their IC50 values of 33.2 and 55.36 μg/mL, respectively. In the α-glucosidase inhibition assay, ON-Cr exhibited moderate inhibitory propensity with an IC50 value of 639.89 μg/mL.ConclusionsThis study investigated Olax nana for the first time for detailed qualitative phytochemical tests, HPLC-DAD finger printing analysis, antioxidant, anticholinesterase and α-glucosidase inhibition assays. The antioxidant and cholinesterase inhibitory results were considerable and can provide scientific basis for further studies on the neuroprotective and anti-Alzheimer’s potentials of this plant. ON-Cr may further be subjected to fractionation and polarity guided fractionation to narrow down the search for isolation of bioactive compounds.

2-Arylbenzofurans from Artocarpus lakoocha and methyl ether analogs with potent cholinesterase inhibitory activity

In vitro screening for acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) inhibitory activities of the Artocarpus lakoocha root-bark extracts revealed interesting results. Bioassay-guided fractionation resulted in the isolation of two new (1 and 2) and six known 2-arylbenzofurans 3–8, along with one stilbenoid 9 and one flavonoid 10. The structures of the isolated compounds were elucidated by UV, IR, 1D- and 2D-NMR and MS spectroscopic data analysis. Compounds 4, 6 and 7 exhibited more potent AChE inhibitory activity (IC50 = 0.87–1.10 μM) than the reference drug, galantamine. Compounds 4, 8 and 9 displayed greater BChE inhibition than the standard drug. The preferential inhibition of BChE over AChE indicated that 4 also showed a promising dual AChE and BChE inhibitor. The synthetic mono-methylated analogs 4a-c and 6a-b were found to be good BChE inhibitors with IC50 values ranging between 0.31 and 1.11 μM. Based on the docking studies, compounds 4 and 6 are well-fitted in the catalytic triad of AChE. Compounds 4 and 6 showed different binding orientations on BChE, and the most potent BChE inhibitor 4 occupied dual binding to both CAS and PAS more efficiently.

Synthesis, biochemical evaluation, and molecular modeling studies of aryl and arylalkyl di-n-butyl phosphates, effective butyrylcholinesterase inhibitors

A series of dialkyl aryl phosphates and dialkyl arylalkyl phosphates were synthesized. Their inhibitory activities were evaluated against acetylcholinesterase (AChE) and butyrylcholinesterase (BChE). The di-n-butyl phosphate series consistently displayed selective inhibition of BChE over AChE. The most potent inhibitors of butyrylcholinesterase were di-n-butyl-3,5-dimethylphenyl phosphate (4b) [KI=1.0±0.4μM] and di-n-butyl 2-naphthyl phosphate (5b) [KI=1.9±0.4μM]. Molecular modeling was used to uncover three subsites within the active site gorge that accommodate the three substituents attached to the phosphate group. Phosphates 4b and 5b were found to bind to these three subsites in analogous fashion with the aromatic groups in both analogs being accommodated by the “lower region,” while the lone pairs on the PO oxygen atoms were oriented towards the oxyanion hole. In contrast, di-n-butyl-3,4-dimethylphenyl phosphate (4a) [KI=9±1μM], an isomer of 4b, was found to orient its aromatic group in the “upper left region” subsite as placement of this group in the “lower region” resulted in significant steric hindrance by a ridge-like region in this subsite. Future studies will be designed to exploit these features in an effort to develop inhibitors of higher inhibitory strength against butyrylcholinesterase.

Synthesis, computational studies and biological evaluation of new 1-acetyl-3-aryl thiourea derivatives as potent cholinesterase inhibitors

A new series of 1-acetyl-3-aryl thioureas (3f1–15) was synthesized by the reaction of acetyl isothiocyanate with a variety of suitably substituted aromatic anilines. The acetyl isothiocyanate was freshly prepared by reaction of corresonding acid chloride with potassium thiocyanate. The structural confirmation of all compounds was carried out by spectroscopic techniques and in case of 3a by X-ray diffraction study. The newly prepared compounds were subjected to computational studies and evaluated for their cholinesterase (acetylcholinesterase and butyrylcholinesterase) inhibition studies. Except 3f9 and 3f15, all the derivatives were found as selective inhibitor of acetylcholinesterase. Compound 3f2 (IC50 ± SEM = 1.99 ± 0.11 µM) was found to be the most potent inhibitor of acetylcholinesterase exhibited ≈11 times greater inhibitory potential than reference inhibitor i.e. neostigmine (IC50 ± SEM = 22.2 ± 3.2 µM). Compound 3f9 was found to be most potent butyrylcholinesterase inhibitor (IC50 ± SEM = 1.33 ± 0.11 µM), exhibiting ≈four times greater selectivity for butyrylcholinesterase over acetylcholinesterase. Molecular docking studies were carried out to determine the binding site interactions of these potent inhibitors with cholinesterases and also supported the experimental observations.

Synthesis of readily available fluorophenylalanine derivatives and investigation of their biological activity

A series of thirty novel N-acetylated fluorophenylalanine-based aromatic amides and esters was synthesized using N-(3-dimethylaminopropyl)-N′-ethylcarbodiimide or phosphorus trichloride in pyridine. They were characterized by spectral methods and screened against various microbes (Mycobacterium tuberculosis, non-tuberculous mycobacteria, other bacteria, fungi), for their inhibition of acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) and cytotoxicity. All amino acids derivatives revealed a moderate inhibition of both cholinesterases with IC50 values for AChE and BChE of 57.88–130.75µM and 8.25–289.0µM, respectively. Some derivatives were comparable or superior to rivastigmine, an established drug. Phenyl 2-acetamido-3-(4-fluorophenyl)propanoate was identified as the selective and most potent inhibitor of BChE. The esterification and amidation of parent acids led to an improved BChE inhibition. The esters are better inhibitors of BChE than the amides. The introduction of NO2 and CH3 groups into aniline ring and CF3 moiety in phenol is translated into lower IC50 values. Seven compounds showed selectivity index higher than 10 for at least one cholinesterase. Especially the esters exhibited a mild activity against Gram-positive bacteria, mycobacteria and several fungal strains with minimum inhibitory concentrations starting from 125µM. The highest susceptibility was recorded for Trichophyton mentagrophytes fungus.

Design, synthesis and evaluation of novel ferulic acid-O-alkylamine derivatives as potential multifunctional agents for the treatment of Alzheimer's disease

A series of novel ferulic acid-O-alkylamines derivatives were designed, synthesized, and evaluated as multitarget-directed ligands against Alzheimer's disease. In vitro studies displayed that all the synthesized target compounds showed impressive inhibitory activity against butyrylcholinesterase (BuChE), significant inhibition/disaggregation of self-induced β-amyloid (Aβ) aggregation and acted as potential antioxidants. Particularly, compound 7f, one of the most potent BuChE inhibitor (IC50 value of 0.021 μM for equine serum BuChE, 8.63 μM for ratBuChE and 0.07 μM for human serum BuChE), was found to be a good acetylcholinesterase (AChE) inhibitor (IC50 = 2.13 μM for electric eel AChE, 1.8 μM for ratAChE and 3.82 μM for human erythrocytes AChE), and the result of molecular docking provided an explanation for its selective BuChE inhibitory activity. Compound 7f also had noteworthy inhibitory effects on self-induced Aβ1-42 aggregation (50.8 ± 0.82%) and was found to disaggregate self-induced Aβ1-42 aggregation (38.7 ± 0.65%), which was further elucidated by the transmission electron microscopy. Meanwhile, compound 7f showed the modest antioxidant activity (0.55 eq of Trolox), good protective effect against H2O2-induced PC12 cell injury, with low toxicity. Moreover, compound 7f could cross the blood-brain barrier (BBB) in vitro. Significantly, compound 7f did not exhibit any acute toxicity in mice at doses up to 1000 mg/kg, and the step-down passive avoidance test showed this compound significantly reversed scopolamine-induced memory deficit in mice. Taken together, the results indicated that compound 7f is a very promising multifunctional agent in the treatment of Alzheimer's disease, particularly the advanced stages of AD.

Amino derivatives of platanic acid act as selective and potent inhibitors of butyrylcholinesterase

A set of thirtyfive 30-norlupan derivatives (2–36) was prepared from the natural triterpenoid platanic acid (PA), and the hydroxyl group at C-3, the carboxyl group at C-17 and the carbonyl group at C-20 were modified. These derivatives were tested for their inhibitory activity for the enzymes acetylcholinesterase (AChE, from electric eel) and butyrylcholinesterase (BChE, from equine serum) using Ellman's assay. Extra enzyme kinetic studies were performed. The most active compound was (3β, 20R)-3-acetyloxy-20-amino-30-norlupan-28-oate (32) showing a Ki value of 0.01 ± 0.003 μM for BChE. This compound proved to be a selective (FB = 851), mixed-type inhibitor for BChE.