Twenty-four novel compounds bearing tetrahydroacridine and N-propargyl moieties have been designed, synthesised, and evaluated in vitro for their anti-cholinesterase and anti-monoamine oxidase activities. Propargyltacrine 23 (IC50 = 21 nM) was the most potent acetylcholinesterase (AChE) inhibitor, compound 20 (IC50 = 78 nM) showed the best inhibitory human butyrylcholinesterase (hBChE) profile, and ligand 21 afforded equipotent and significant values on both ChEs (human AChE [hAChE]: IC50 = 0.095 ± 0.001 µM; hBChE: IC50 = 0.093 ± 0.003 µM). Regarding MAO inhibition, compounds 7, 15, and 25 demonstrated the highest inhibitory potential towards hMAO-B (IC50 = 163, 40, and 170 nM, respectively). In all, compounds 7, 15, 20, 21, 23, and 25 exhibiting the most balanced pharmacological profile, were submitted to permeability and cell viability tests. As a result, 7-phenoxy-N-(prop-2-yn-1-yl)-1,2,3,4-tetrahydroacridin-9-amine hydrochloride (15) has been identified as a permeable agent that shows a balanced pharmacological profile [IC50 (hAChE) = 1.472 ± 0.024 µM; IC50 (hBChE) = 0.659 ± 0.077 µM; IC50 (hMAO-B) = 40.39 ± 5.98 nM], and consequently, as a new hit-ligand that deserves further investigation, in particular in vivo analyses, as the preliminary cell viability test results reported here suggest that this is a relatively safe therapeutic agent.

• Keywords
• Alzheimer’s disease, Cholinesterase inhibitor, monoamine oxidase inhibitor, propargyl amines, tacrine,
• MeSH
• Acetylcholinesterase metabolism   MeSH
• Alzheimer Disease * drug therapy   MeSH
• Amines MeSH
• Butyrylcholinesterase * metabolism   MeSH
• Cholinesterase Inhibitors pharmacology   therapeutic use   MeSH
• Monoamine Oxidase Inhibitors pharmacology   MeSH
• Humans MeSH
• Ligands MeSH
• Monoamine Oxidase MeSH
• Oxidoreductases MeSH
• Drug Design MeSH
• Tacrine therapeutic use   MeSH
• Structure-Activity Relationship MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Acetylcholinesterase MeSH
• Amines MeSH
• Butyrylcholinesterase * MeSH
• Cholinesterase Inhibitors MeSH
• Monoamine Oxidase Inhibitors MeSH
• Ligands MeSH
• Monoamine Oxidase MeSH
• Oxidoreductases MeSH
• Tacrine MeSH

Alzheimer's disease (AD) is a complex disorder with unknown etiology. Currently, only symptomatic therapy of AD is available, comprising cholinesterase inhibitors and N-methyl-d-aspartate (NMDA) receptor antagonists. Drugs targeting only one pathological condition have generated only limited efficacy. Thus, combining two or more therapeutic interventions into one molecule is believed to provide higher benefit for the treatment of AD. In the presented study, we designed, synthesized, and biologically evaluated 15 novel fluoren-9-amine derivatives. The in silico prediction suggested both the oral availability and permeation through the blood-brain barrier (BBB). An initial assessment of the biological profile included determination of the cholinesterase inhibition and NMDA receptor antagonism at the GluN1/GluN2A and GluN1/GluN2B subunits, along with a low cytotoxicity profile in the CHO-K1 cell line. Interestingly, compounds revealed a selective butyrylcholinesterase (BChE) inhibition pattern with antagonistic activity on the NMDARs. Their interaction with butyrylcholinesterase was elucidated by studying enzyme kinetics for compound 3c in tandem with the in silico docking simulation. The docking study showed the interaction of the tricyclic core of new derivatives with Trp82 within the anionic site of the enzyme in a similar way as the template drug tacrine. From the kinetic analysis, it is apparent that 3c is a competitive inhibitor of BChE.

• Keywords
• Alzheimer’s disease, N-methyl-d-aspartate receptor, acetylcholinesterase, butyrylcholinesterase, fluorene, in silico, in vitro, multi-target directed ligands,
• MeSH
• Alzheimer Disease drug therapy   enzymology   genetics   pathology   MeSH
• Butyrylcholinesterase chemistry   drug effects   genetics   MeSH
• CHO Cells MeSH
• Cholinesterase Inhibitors chemistry   pharmacology   MeSH
• Cricetulus MeSH
• Fluorenes chemistry   pharmacology   MeSH
• Blood-Brain Barrier drug effects   MeSH
• Enzyme Inhibitors pharmacology   MeSH
• Humans MeSH
• Computer Simulation MeSH
• Receptors, N-Methyl-D-Aspartate antagonists & inhibitors   genetics   MeSH
• Animals MeSH
• Check Tag
• Humans MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Butyrylcholinesterase MeSH
• Cholinesterase Inhibitors MeSH
• fluorene MeSH Browser
• Fluorenes MeSH
• Enzyme Inhibitors MeSH
• N-methyl D-aspartate receptor subtype 2A MeSH Browser
• NR2B NMDA receptor MeSH Browser
• Receptors, N-Methyl-D-Aspartate MeSH

Tacrine (THA), the first clinically effective acetylcholinesterase (AChE) inhibitor and the first approved drug for the treatment of Alzheimer's disease (AD), was withdrawn from the market due to its side effects, particularly its hepatotoxicity. Nowadays, THA serves as a valuable scaffold for the design of novel agents potentially applicable for AD treatment. One such compound, namely 7-methoxytacrine (7-MEOTA), exhibits an intriguing profile, having suppressed hepatotoxicity and concomitantly retaining AChE inhibition properties. Another interesting class of AChE inhibitors represents Huprines, designed by merging two fragments of the known AChE inhibitors-THA and (-)-huperzine A. Several members of this compound family are more potent human AChE inhibitors than the parent compounds. The most promising are so-called huprines X and Y. Here, we report the design, synthesis, biological evaluation, and in silico studies of 2-methoxyhuprine that amalgamates structural features of 7-MEOTA and huprine Y in one molecule.

• Keywords
• 2-methoxyhuprine, 7-MEOTA, Alzheimer’s disease, acetylcholinesterase, butyrylcholinesterase, huprine Y, tacrine,
• MeSH
• Acetylcholinesterase MeSH
• Enzyme Activation drug effects   MeSH
• Alzheimer Disease drug therapy   MeSH
• Aminoquinolines chemical synthesis   chemistry   pharmacology   MeSH
• Butyrylcholinesterase MeSH
• Cholinesterase Inhibitors chemistry   pharmacology   MeSH
• Blood-Brain Barrier metabolism   MeSH
• Heterocyclic Compounds, 4 or More Rings chemistry   pharmacology   MeSH
• Hydrolysis MeSH
• Inhibitory Concentration 50 MeSH
• Catalytic Domain MeSH
• Humans MeSH
• Molecular Conformation MeSH
• Models, Molecular MeSH
• Molecular Structure MeSH
• Cell Line, Tumor MeSH
• Drug Discovery * MeSH
• Permeability MeSH
• Drug Design MeSH
• Tacrine analogs & derivatives   chemistry   pharmacology   MeSH
• Protein Binding MeSH
• Binding Sites MeSH
• Cell Survival drug effects   MeSH
• Structure-Activity Relationship MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• 7-methoxytacrine MeSH Browser
• Acetylcholinesterase MeSH
• Aminoquinolines MeSH
• Butyrylcholinesterase MeSH
• Cholinesterase Inhibitors MeSH
• Heterocyclic Compounds, 4 or More Rings MeSH
• huprine Y MeSH Browser
• Tacrine MeSH