Search for multifunctional agents against Alzheimer's disease among non-imidazole histamine H3 receptor ligands. In vitro and in vivo pharmacological evaluation and computational studies of piperazine derivatives.

In the search for new treatments for complex disorders such as Alzheimer's disease the Multi-Target-Directed Ligands represent a very promising approach. The aim of the present study was to identify multifunctional compounds among several series of non-imidazole histamine H3 receptor ligands, derivatives of 1-[2-thiazol-5-yl-(2-aminoethyl)]-4-n-propylpiperazine, 1-[2-thiazol-4-yl-(2-aminoethyl)]-4-n-propylpiperazine and 1-phenoxyalkyl-4-(amino)alkylopiperazine using in vitro and in vivo pharmacological evaluation and computational studies. Performed in vitro assays showed moderate potency of tested compounds against acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE). Molecular modeling studies have revealed possible interactions between the active compounds and both AChE and BuChE as well as the human H3 histamine receptor. Computational studies showed the high drug-likeness of selected compounds with very good physicochemical profiles. The parallel artificial membrane permeation assay proved outstanding blood-brain barrier penetration in test conditions. The most promising compound, A12, chemically methyl(4-phenylbutyl){2-[2-(4-propylpiperazin-1-yl)-1,3-thiazol-5-yl]ethyl}amine, possesses good balanced multifunctional profile with potency toward studied targets - H3 antagonist activity (pA2 = 8.27), inhibitory activity against both AChE (IC50 = 13.96 µM), and BuChE (IC50 = 14.62 µM). The in vivo pharmacological studies revealed the anti-amnestic properties of compound A12 in the passive avoidance test on mice.

Novel carbamate derivatives as selective butyrylcholinesterase inhibitors.

Selective butyrylcholinesterase inhibitors could be the promising drug candidates, used in treatment of Alzheimer's disease. The study describes the synthesis and biological activity of novel carbamate derivatives with N-phenylpiperazine, N-benzylpiperazine and 4-benzylpiperidine moieties. Biological studies revealed that most of these compounds displayed significant activity against BuChE. Compound 16 (3-(4-phenyl-piperazin-1-ylmethyl)-phenyl phenylcarbamate) turned out to be the most active (IC50 = 2.00 µM for BuChE). For all synthesized compounds lipophilicity and other physicochemical properties were calculated using computer programs. Relationship between these properties and activity was also checked. Binding mode with enzyme and the ensuing differences in activity were explained by the molecular modeling studies.

Lipophilic properties of anti-Alzheimer's agents determined by micellar electrokinetic chromatography and reversed-phase thin-layer chromatography.

Lipophilicity as one of the most important physicochemical properties of the biologically active compounds is closely related to their pharmacokinetic parameters and therefore, it is taken into account at the design stage of new drugs. Among the novel, fast, and reliable methods for determination of the lipophilicity of compounds micellar electrokinetic chromatography (MEKC) is considered to be an appropriate one for bioactive molecules, as it closely mimics the physiological conditions. In this paper MEKC was used for the estimation of log P values for 49 derivatives of phthalimide, tetrahydroisochinoline and indole, designed and synthesized as potential anti-Alzheimer's agents with cholinesterase inhibitory activity. RP-TLC method was applied for determination of another lipophilicity descriptor - RM0 . The results of both experimental methods were compared with each other giving satisfactory correlation (R = 0.784), and with computational methods (Marvin, ChemOffice Software) resulting in weaker correlation (R = 0.466-0.687). The lipophilicity-activity relationship was finally established, showing significant influence of lipophilicity on cholinesterase inhibition in some subgroups of phthalimide derivatives.

Synthesis, Molecular Modelling and Biological Evaluation of Novel Heterodimeric, Multiple Ligands Targeting Cholinesterases and Amyloid Beta.

Cholinesterases and amyloid beta are one of the major biological targets in the search for a new and efficacious treatment of Alzheimer's disease. The study describes synthesis and pharmacological evaluation of new compounds designed as dual binding site acetylcholinesterase inhibitors. Among the synthesized compounds, two deserve special attention--compounds 42 and 13. The former is a saccharin derivative and the most potent and selective acetylcholinesterase inhibitor (EeAChE IC50 = 70 nM). Isoindoline-1,3-dione derivative 13 displays balanced inhibitory potency against acetyl- and butyrylcholinesterase (BuChE) (EeAChE IC50 = 0.76 µM, EqBuChE IC50 = 0.618 µM), and it inhibits amyloid beta aggregation (35.8% at 10 µM). Kinetic studies show that the developed compounds act as mixed or non-competitive acetylcholinesterase inhibitors. According to molecular modelling studies, they are able to interact with both catalytic and peripheral active sites of the acetylcholinesterase. Their ability to cross the blood-brain barrier (BBB) was confirmed in vitro in the parallel artificial membrane permeability BBB assay. These compounds can be used as a solid starting point for further development of novel multifunctional ligands as potential anti-Alzheimer's agents.

SEARCH FOR POTENTIAL CHOLINESTERASE INHIBITORS FROM THE ZINC DATABASE BY VIRTUAL SCREENING METHOD.

A virtual screening of the ZINC database was applied for the identification of novel cholinesterase inhibitors. The first step allowed to select compounds with favorable physicochemical properties. Then, the compounds were screened with the pharmacophore models built using crystal structures of donepezil, tacrine, decamethonium and bis-7-tacrine with acetylcholinesterase and well characterized interactions of bis-nor-meptazinol with butyrylcholinesterase. The selected compounds from the group of donepezil were docked to acetyl-cholinesterase giving 7 structures for further studies. These compounds were tested against cholinesterases and two of them, 1-[4-(1H-indol-3-ylmethyl)piperazin-1-yl]-2-phenoxyethanone 2 and 2-[(1-benzylpiperidine-4- yl)amino]-1-phenylethanol 4 displayed, respectively, 50.1% and 79.5% of inhibition against butyryl- cholinesterase at the concentration of 100 µM.

Structure-based search for new inhibitors of cholinesterases.

Cholinesterases are important biological targets responsible for regulation of cholinergic transmission, and their inhibitors are used for the treatment of Alzheimer's disease. To design new cholinesterase inhibitors, of different structure-based design strategies was followed, including the modification of compounds from a previously developed library and a fragment-based design approach. This led to the selection of heterodimeric structures as potential inhibitors. Synthesis and biological evaluation of selected candidates confirmed that the designed compounds were acetylcholinesterase inhibitors with IC50 values in the mid-nanomolar to low micromolar range, and some of them were also butyrylcholinesterase inhibitors.