Rapid discovery and crystallography study of highly potent and selective butylcholinesterase inhibitors based on oxime-containing libraries and conformational restriction strategies.

Butyrylcholinesterase is regarded as a promising drug target in advanced Alzheimer's disease. In order to identify highly selective and potent BuChE inhibitors, a 53-membered compound library was constructed via the oxime-based tethering approach based on microscale synthesis. Although A2Q17 and A3Q12 exhibited higher BuChE selectivity versus acetylcholinesterase, the inhibitory activities were unsatisfactory and A3Q12 did not inhibit Aß1-42 peptide self-induced aggregation. With A2Q17 and A3Q12 as leads, a novel series of tacrine derivatives with nitrogen-containing heterocycles were designed based on conformation restriction strategy. The results demonstrated that 39 (IC50 = 3.49 nM) and 43 (IC50 = 7.44 nM) yielded much improved hBuChE inhibitory activity compared to the lead A3Q12 (IC50 = 63 nM). Besides, the selectivity indexes (SI = AChE IC50 / BChE IC50) of 39 (SI = 33) and 43 (SI = 20) were also higher than A3Q12 (SI = 14). The results of the kinetic study showed that 39 and 43 exhibited a mixed-type inhibition against eqBuChE with respective Ki values of 1.715 nM and 0.781 nM. And 39 and 43 could inhibit Aß1-42 peptide self-induced aggregation into fibril. X-ray crystallography structures of 39 or 43 complexes with BuChE revealed the molecular basis for their high potency. Thus, 39 and 43 are deserve for further study to develop potential drug candidates for the treatment of Alzheimer's disease.

Total Synthesis of Pulmonarin B and Design of Brominated Phenylacetic Acid/Tacrine Hybrids: Marine Pharmacophore Inspired Discovery of New ChE and Aß Aggregation Inhibitors.

A marine natural product, pulmonarin B (1), and a series of related tacrine hybrid analogues were synthesized and evaluated as cholinesterase (ChE) inhibitors. The in vitro ChE assay results revealed that 1 showed moderate dual acetylcholinesterase (AChE)/ butyrylcholinesterase (BChE) inhibitory activity, while the hybrid 12j proved to be the most potent dual inhibitor among the designed derivatives, being almost as active as tacrine. Molecular modeling studies together with kinetic analysis suggested that 12j interacted with both the catalytic active site and peripheral anionic site of AChE. Compounds 1 and 12j could also inhibit self-induced and AChE-induced Aß aggregation. In addition, the cell-based assay against the human hepatoma cell line (HepG2) revealed that 1 and 12j did not show significant hepatotoxicity compared with tacrine and donepezil. Taken together, the present study confirmed that compound 1 was a potential anti-Alzheimer's disease (AD) hit, and 12j could be highlighted as a multifunctional lead compound for anti-AD drug development.

Syntheses of coumarin-tacrine hybrids as dual-site acetylcholinesterase inhibitors and their activity against butylcholinesterase, Aß aggregation, and ß-secretase.

Exploring small-molecule acetylcholinesterase (AChE) inhibitors to slow the breakdown of acetylcholine (Ach) represents the mainstream direction for Alzheimer's disease (AD) therapy. As the first acetylcholinesterase inhibitor approved for the clinical treatment of AD, tacrine has been widely used as a pharmacophore to design hybrid compounds in order to combine its potent AChE inhibition with other multi-target profiles. In present study, a series of novel tacrine-coumarin hybrids were designed, synthesized and evaluated as potent dual-site AChE inhibitors. Moreover, compound 1g was identified as the most potent candidate with about 2-fold higher potency (Ki=16.7nM) against human AChE and about 2-fold lower potency (Ki=16.1nM) against BChE than tacrine (Ki=35.7nM for AChE, Ki=8.7nM for BChE), respectively. In addition, some of the tacrine-coumarin hybrids showed simultaneous inhibitory effects against both Aß aggregation and ß-secretase. We therefore conclude that tacrine-coumarin hybrid is an interesting multifunctional lead for the AD drug discovery.

The biological activities of butyrylcholinesterase inhibitors.

Acetylcholinesterase (AChE) inhibitor is the first choice for the treatment of Alzheimer's disease (AD), but it has some defects, such as dose limitation and unsatisfactory long-term treatment effect. Recent studies have shown that butyrylcholinesterase (BuChE) inhibitors or double acetyl and butyryl cholinesterase inhibitors have better curative effects on AD, and the side effects are lower than those of specific AChE inhibitors. Dual target cholinesterase inhibitors have become a new hotspot in the research of anti-AD drugs. Herein, the synthesis and bioactivities of BuChE inhibitors were reviewed.

Design, synthesis, in-silico and biological evaluation of novel chalcone-O-carbamate derivatives as multifunctional agents for the treatment of Alzheimer's disease.

To discover multifunctional agents for the treatment of Alzheimer's disease (AD), a series of chalcone-O-carbamate derivatives was designed and synthesized based on the multitarget-directed ligands strategy. The in vitro biological activities were evaluated including AChE/BChE inhibition, MAO-A/MAO-B inhibition, antioxidant activities, Aß1-42 aggregation inhibition, metal-chelating properties and neuroprotective effects against H2O2-induced PC12 cell injury. The results showed compounds 5b and 5h indicated highly selective BChE inhibitory activity with IC50 values of 3.1 µM and 1.2 µM, respectively and showed highly selective MAO-B inhibitory potency with IC50 values of 1.3 µM and 3.7 µM, respectively. In addition, compounds 5b and 5h could inhibit self-induced Aß1-42 aggregation with 63.9% and 53.1% inhibition percent rate, respectively. Particularly, compound 5b was a potent antioxidant agent and neuroprotectant, as well as a selective metal chelator by chelating Cu2+ and Al3+. Moreover, compound 5b could inhibit and disaggregate Cu2+-induced Aß1-42 aggregation, which was further supported by the TEM images. Furthermore, compounds 5b and 5h could cross the blood-brain barrier (BBB) in vitro and conformed to the Lipinski's rule of five. Finally, the in vivo assay exhibited that compound 5b could improve scopolamine-induced cognitive impairment. Taken together, these results revealed that compound 5b might be a potential multifunctional agent for the treatment of AD, and deserved to do further structure optimization.

Rational Approaches, Design Strategies, Structure Activity Relationship and Mechanistic Insights for Esterase Inhibitors.

BACKGROUND: Esterase is an enzyme that splits esters into an acid and alcohol. Varieties of esterases are present in human body to control diverse set of cellular processes and execute their specific functions. It can be seen that any increase in metabolites produced by these enzymes lead to severe pathological conditions like Alzheimer disease, hypercholesterolemia etc. Objective: Numerous esterase inhibitors have been developed and reported by the researchers around the globe, but not systematically summarized yet. Therefore, this assemblage focuses on various reported esterase inhibitors during recent past with detailed account of the design strategies employed for the synthesis of novel drug entities. The article also highlights the structure activity relationship along with mechanistic insights revealed during the biological evaluation of inhibitors as esterase inhibition. The interactions with the amino acid residues responsible for esterase inhibitory potential of molecules have also been discussed. This compilation will be of great interest for the researchers working in the area of esterase inhibitors. CONCLUSION: Rivastigmine derivatives (44-53), tacrine-piperazine hybrid (136), coumarin-benzofuran derivative (169), coumarin-benzylpiperidine hybrid (181) and phenylcinnamide derivative (220) found to be exerting cholinesterase inhibition with IC50 below the range of 1 nM. Whereas, flavone (258) has displayed anticholesterol esterase potential below 1 nM. Benzil like derivative, (273) has also been designed and reported to possess remarkable inhibitory potential (IC50 < 1 nM) against carboxylesterase. These representative results place them in forefront as potential future drug candidates to further develop potent and specific esterase inhibitors.

Anticholinesterase potential of flavonols from paper mulberry (Broussonetia papyrifera) and their kinetic studies.

It is necessary to develop food additives to help treat chronic disorders like neurodegenerative diseases from medicinal plants. Ethanol extracts of paper mulberry were found to display significant inhibition against cholinesterases, enzymes that are strongly linked with Alzheimer's disease (AD). The active components were identified as prenylated flavonols (2-4) that inhibited two related human cholinesterases in a dose-dependent manner, with IC50's ranging between 0.8 and 3.1µM and between 0.5 and 24.7µM against human acetylcholinesterase (hAChE) and butylcholinesterase (BChE), respectively. Prenyl groups within these flavonols were found to play a critical role for inhibition because the parent compound 1, quercetin, was inactive (IC50>500µM) towards the target enzymes. Flavonols (2-4) showed mixed inhibition kinetics as well as slow and time-dependent reversible inhibition toward hAChE. The affinity between protein and inhibitors was investigated using fluorescence quenching. The affinity constants (KSA) of inhibitors increased in proportion to their inhibitory potencies.

Changes in learning and memory ability and brain cholinesterase activity in the rats with coal burning fluorosis / 中国地方病学杂志

Objective To observe the influence of coal burning fluorosis on learning and memory ability in rats and reveal its possible mechanisms. Methods Healthy 48 SD rats were divided into control, low-fluoride and high-fluoride group. All rats in fluoride exposed groups were fed with the eom polluted by drying processes with burning coal containing high level of fluoride obtained from the endemic fluorosis area to produce the animal model of fluorosis. The experiment period were 3,6 mouths, respectively. The ability of leaning and memory was measured by Morris test and cholinesterase activity detected by photometric method at 3 or 6 month after experiment, respectively. Results Fluoride contents signifieantlly influenced the escape latency, the numbers of crossing the platforms and the time of staying the platforms(the value of F was 29.29,6.47,6.50, respectively, P<0.01).In addition, the numbers of crossing the platforms and the time of staying the platforms were influenced by the exposed time(the value of F was 16.11,45.59, P<0.01). Furthermore, the fluoride contents and the exposed time had an interaction between the numbers of crossing the platforms and the time of staying the platforms (the value of F was 4.67,5.68, P<0.05 or<0.01). Three months after the experiment, the mean values of escape latency [(14.71± 4.85)s] of rats in highly fluoride exposed group were significantly prolonged as compared with controls [(9.28±4.22)s]; 6 month after the experiment, the mean values of escape latency[(12.42±8.03)s, (17.48± 8.05)s] of rats in both groups exposed to fluoride were significantly prolonged as compared to controls [(7.04± 3.29)s, P<0.05]. The decreased numbers of crossing the platforms[(1.62±0.87)number] and the declined time of staying the platforms[(16.70±5.02)s] were found in the rats exposed to high fluoride as compared to controls [(3.53±1.67 )number, (23.33±5.35)s, P<0.05]. The fluoride contents obviously influenced the activities of acetylcholinesterase and butylcolinesterase (the value of F was 12.83,13.27, P<0.01). On the other hand, the times of breeding also influnced the activities of butylcolinesterase (the value of F was 16.26, P<0.01). In 3 months of the experiment, the activities of butylcolinesterase [(0.55±0.12)kU/g] in low fluoride exposed group were significantly decreased in comparison with controls[(0.73±0.10)kU/g, P<0.05]. The activities of acetylcholinesterase[(0.62±0.42)kU/g] and butylcolioesterase[(0.58±0.10)kU/g] in high fluoride group were significantly decreased as compared to eontrois[(1.41±0.52), (0.73±0.10)kU/g, P<0.05]. The correlation analysis showed that there was a negative correlation between the cholinesterase and the escape latency(r=-0.68, P< 0.01), and a positive correlation between the cholinesterase and the time of staying the platforms(r=0.57, P< 0.01). Conclusions The ability of learning and memory in rats with coal buring fluorosis was decreased, which might be connected to the decreased activity of cholinesterase in a dose-effect correlation.