Chemical modifications of cinchona alkaloids lead to enhanced inhibition of human butyrylcholinesterase.

Butyrylcholinesterase (BChE) inhibitors were identified from a collection containing cinchonine, cinchonidine and synthetic derivatives, and further characterized using cytotoxicity and molecular docking studies. The most active ones were: (10 triple bond)-10,11-dibromo-10,11-dihydrocinchonidine (11), a competitive inhibitor with Ki = 3.45 +/- 0.39 microM, and IC50 BChE = 9.83 +/- 0.30 microM/human (h)BChE = 34.47 +/- 4.63 and O-(trimethylsilyl)cinchonine (15), a mixed inhibitor with Kiuc = 1.73 +/- 0.46 microM and Kic = 0.85 +/- 0.26 microM, and IC50 BChE = 0.56 +/- 0.14 microM/hBChE = 0.24 +/- 0.04. In cytotoxicity experiments, > or = 80% of the cells remained viable when exposed to concentrations of up to 80 microM of both inhibitors in four different cell lines, including neurons. Due to the bulkier trimethylsilyl side group of 15, it covered the active site of hBChE better than 11 with an OH-group while not being able to fit into the active site gorge of hAChE, thus explaining the selectivity of 15 towards hBChE.

Identification and characterization of diarylimidazoles as hybrid inhibitors of butyrylcholinesterase and amyloid beta fibril formation.

In this contribution, a chemical collection of aromatic compounds was screened for inhibition on butyrylcholinesterase (BChE)'s hydrolase activity using Ellman's reaction. A set of diarylimidazoles was identified as highly selective inhibitors of BChE hydrolase activity and amyloid ß (Aß) fibril formation. New derivatives were synthesized resulting in several additional hits, from which the most active was 6c, 4-(3-ethylthiophenyl)-2-(3-thienyl)-1H-imidazole, an uncompetitive inhibitor of BChE hydrolase activity (IC50 BChE=0.10 µM; K(i)=0.073 ± 0.011 µM) acting also on Aß fibril formation (IC50=5.8 µM). With the aid of structure-activity relationship (SAR) studies, chemical motifs influencing the BChE inhibitory activity of these imidazoles were proposed. These bifunctional inhibitors represent good tools in basic studies of BChE and/or promising lead molecules for AD therapy.

Discovery of dual binding site acetylcholinesterase inhibitors identified by pharmacophore modeling and sequential virtual screening techniques.

Dual binding site acetylcholinesterase (AChE) inhibitors are promising for the treatment of Alzheimer's disease (AD). They alleviate the cognitive deficits and AD-modifying agents, by inhibiting the ß-amyloid (Aß) peptide aggregation, through binding to both the catalytic and peripheral anionic sites, the so called dual binding site of the AChE enzyme. In this Letter, chemical features based 3D-pharmacophore models were developed based on the eight potent and structurally diverse AChE inhibitors (I-VIII) obtained from high-throughput in vitro screening technique. The best 3D-pharmacophore model, Hypo1, consists of two hydrogen-bond acceptor lipid, one hydrophobe, and two hydrophobic aliphatic features obtained by Catalyst/HIPHOP algorithm adopted in Discovery studio program. Hypo1 was used as a 3D query in sequential virtual screening study to filter three small compound databases. Further, a total of nine compounds were selected and followed on in vitro analysis. Finally, we identified two leads--Specs1 (IC(50)=3.279 µM) and Spec2 (IC(50)=5.986 µM) dual binding site compounds from Specs database, having good AChE enzyme inhibitory activity.