Synthesis of New Biscoumarin Derivatives, In Vitro Cholinesterase Inhibition, Molecular Modelling and Antiproliferative Effect in A549 Human Lung Carcinoma Cells.

A series of novel C4-C7-tethered biscoumarin derivatives (12a-e) linked through piperazine moiety was designed, synthesized, and evaluated biological/therapeutic potential. Biscoumarin 12d was found to be the most effective inhibitor of both acetylcholinesterase (AChE, IC50 = 6.30 µM) and butyrylcholinesterase (BChE, IC50 = 49 µM). Detailed molecular modelling studies compared the accommodation of ensaculin (well-established coumarin derivative tested in phase I of clinical trials) and 12d in the human recombinant AChE (hAChE) active site. The ability of novel compounds to cross the blood-brain barrier (BBB) was predicted with a positive outcome for compound 12e. The antiproliferative effects of newly synthesized biscoumarin derivatives were tested in vitro on human lung carcinoma cell line (A549) and normal colon fibroblast cell line (CCD-18Co). The effect of derivatives on cell proliferation was evaluated by MTT assay, quantification of cell numbers and viability, colony-forming assay, analysis of cell cycle distribution and mitotic activity. Intracellular localization of used derivatives in A549 cells was confirmed by confocal microscopy. Derivatives 12d and 12e showed significant antiproliferative activity in A549 cancer cells without a significant effect on normal CCD-18Co cells. The inhibition of hAChE/human recombinant BChE (hBChE), the antiproliferative activity on cancer cells, and the ability to cross the BBB suggest the high potential of biscoumarin derivatives. Beside the treatment of cancer, 12e might be applicable against disorders such as schizophrenia, and 12d could serve future development as therapeutic agents in the prevention and/or treatment of Alzheimer's disease.

Design and synthesis of novel tacrine-indole hybrids as potential multitarget-directed ligands for the treatment of Alzheimer's disease.

The authors report on the synthesis and biological evaluation of new compounds whose structure combines tacrine and indole moieties. Tacrine-indole heterodimers were designed to inhibit cholinesterases and ß-amyloid formation, and to cross the blood-brain barrier. The most potent new acetylcholinesterase inhibitors were compounds 3c and 4d (IC50 = 25 and 39 nM, respectively). Compound 3c displayed considerably higher selectivity for acetylcholinesterase relative to human plasma butyrylcholinesterase in comparison to compound 4d (selectivity index: IC50 [butyrylcholinesterase]/IC50 [acetylcholinesterase] = 3 and 0.6, respectively). Furthermore, compound 3c inhibited ß-amyloid-dependent amyloid nucleation in the yeast-based prion nucleation assay and displayed no dsDNA destabilizing interactions with DNA. Compounds 3c and 4d displayed a high probability of crossing the blood-brain barrier. The results support the potential of 3c for future development as a dual-acting therapeutic agent in the prevention and/or treatment of Alzheimer's disease.

Tacrine-Coumarin Derivatives as Topoisomerase Inhibitors with Antitumor Effects on A549 Human Lung Carcinoma Cancer Cell Lines.

A549 human lung carcinoma cell lines were treated with a series of new drugs with both tacrine and coumarin pharmacophores (derivatives 1a-2c) in order to test the compounds' ability to inhibit both cancer cell growth and topoisomerase I and II activity. The ability of human topoisomerase I (hTOPI) and II to relax supercoiled plasmid DNA in the presence of various concentrations of the tacrine-coumarin hybrid molecules was studied with agarose gel electrophoresis. The biological activities of the derivatives were studied using MTT assays, clonogenic assays, cell cycle analysis and quantification of cell number and viability. The content and localization of the derivatives in the cells were analysed using flow cytometry and confocal microscopy. All of the studied compounds were found to have inhibited topoisomerase I activity completely. The effect of the tacrine-coumarin hybrid compounds on cancer cells is likely to be dependent on the length of the chain between the tacrine and coumarin moieties (1c, 1d = tacrine-(CH2)8-9-coumarin). The most active of the tested compounds, derivatives 1c and 1d, both display longer chains.

In vitro investigating of anticancer activity of new 7-MEOTA-tacrine heterodimers.

A combination of biochemical, biophysical and biological techniques was used to study calf thymus DNA interaction with newly synthesized 7-MEOTA-tacrine thiourea 12-17 and urea heterodimers 18-22, and to measure interference with type I and II topoisomerases. Their biological profile was also inspected in vitro on the HL-60 cell line using different flow cytometric techniques (cell cycle distribution, detection of mitochondrial membrane potential dissipation, and analysis of metabolic activity/viability). The compounds exhibited a profound inhibitory effect on topoisomerase activity (e.g. compound 22 inhibited type I topoisomerase at 1 µM concentration). The treatment of HL-60 cells with the studied compounds showed inhibition of cell growth especially with hybrids containing thiourea (14-17) and urea moieties (21 and 22). Moreover, treatment of human dermal fibroblasts with the studied compounds did not indicate significant cytotoxicity. The observed results suggest beneficial selectivity of the heterodimers as potential drugs to target cancer cells.

Proliferation inhibition of novel diphenylamine derivatives.

Nonsteroidal anti-inflammatory drugs (NSAIDs) are the most widely used drugs in the world but some NSAIDs such as diclofenac and tolfenamic acid display levels of cytotoxicity, an effect which has been attributed to the presence of diphenylamine contained in their structures. A novel series of diphenylamine derivatives were synthetised and evaluated for their cytotoxic activities and proliferation inhibition. The most active compounds in the cytotoxicity tests were derivative 6g with an IC50 value of 2.5 ±â€¯1.1 × 10-6 M and derivative 6f with an IC50 value of 6.0 ±â€¯3.0 × 10-6 M (L1210 cell line) after 48 h incubation. The results demonstrate that leukemic L1210 cells were much more sensitive to compounds 6f and 6g than the HEK293T cells (IC50 = 35 × 10-6 M for 6f and IC50 > 50 × 10-6 M for 6g) and NIH-3T3 (IC50 > 50 × 10-6 M for both derivatives). The IC50 values show that these substances may selectively kill leukemic cells over non-cancer cells. Cell cycle analysis revealed that a primary trend of the diphenylamine derivatives was to arrest the cells in the G1-phase of the cell cycle within the first 24 h. UV-visible, fluorescence spectroscopy and circular dichroism were used in order to study the binding mode of the novel compounds with DNA. The binding constants determined by UV-visible spectroscopy were found to be in the range of 2.1-8.7 × 104 M-1. We suggest that the observed trend for binding constant K is likely to be a result of different binding thermodynamics accompanying the formation of the complexes.

Tacrine-coumarin and Tacrine-7-chloroquinoline Hybrids with Thiourea Linkers: Cholinesterase Inhibition Properties, Kinetic Study, Molecular Docking and Permeability Assay for Blood-brain Barrier.

BACKGROUND: The design of new heterodimeric dual binding site acetylcholinesterase inhibitors constitutes the main goal-directed to the development of new anticholinesterase agents with the expanded pharmacological profile. Multi-target compounds are usually designed by combining in a hybrid molecule with two or more pharmacophoric moieties that are known to enable interaction with the selected molecular targets. METHODS: All compounds were tested for their inhibitory activity on human AChE/BChE. The Ellman´s method was used to determine inhibition kinetics and IC50 values. In order to predict passive bloodbrain penetration of novel compounds, modification of the parallel artificial membrane permeation assay has been used. Docking studies were performed in order to predict the binding modes of new hybrids with hAChE/ hBChE respectively. RESULTS: In this study, we described the design, synthesis, and evaluation of series tacrine-coumarin and tacrine-quinoline compounds which were found to show potential inhibition of ChEs and penetration of the blood-brain barrier. CONCLUSION: Tacrine-quinoline hybrids 7a exhibited the highest activity towards hBChE (IC50 = 0.97 µmol) and 7d towards hAChE (IC50 = 0.32 µmol). Kinetic and molecular modelling studies revealed that 7d was a mixed-type AChE inhibitor (Ki = 1.69 µmol) and 7a was a mixed-type BChE inhibitor (Ki = 1.09 µmol). Moreover, hybrid 5d and 7c could penetrate the CNS.

Lysozyme amyloid fibrillization in presence of tacrine/acridone-coumarin heterodimers.

Amyloid aggregates of proteins are one of the most abundant and important naturally occurring self-associated assemblies. Formation of poly/peptide amyloid aggregates is also associated with the widely spread diseases, so called amyloidosis, which include Alzheimer's disease, diabetes mellitus and lysozyme amyloidosis. These disorders are still incurable and novel therapeutical approaches are focused on using small molecules for inhibition of amyloid aggregation. We have observed effect of three structurally distinct groups of tacrine/acridone - coumarin heterodimers on hen egg white (HEW) lysozyme fibrillization in vitro. The ability of heterodimers to interfere with lysozyme amyloid aggregation was examined using Thioflavin T fluorescence assay, atomic force microscopy and docking method. The obtained data suggest that inhibitory effect of heterodimers on lysozyme fibrillization depends on their composition. We have shown that tacrine-coumarin heterodimers with alkylenediamine linker are the most effective inhibitors of lysozyme fibrillization. The inhibitory activities were quantified through IC50 values; the most potent heterodimers interfere with lysozyme aggregation in the scale of micromolar concentrations (19.2 µM-105.4 µM). The molecular docking showed that the modes of possible interactions involved in the binding are mainly hydrophobic interactions, hydrogen bonding and van der Waals interactions. Studied heterodimers had none or weak cytotoxic effect on human neuroblastoma cells. The obtained results can be helpful for the design and development of new therapeutics for amyloid-related diseases.

Anti-Cancer Effect of Tacrine-Coumarin Derivatives on Diverse Human and Mouse Cancer Cell Lines.

Acridine derivatives were first used as antibacterial and antiparasitic agents, later as antimalarial and anti-HIV drugs, and now as potentially anti-cancer agents due to their high cytotoxic activity. Due to their serious adverse effects, new synthetic derivatives were introduced and tested based on modified naturally occurring substances, such as acridone derivatives, which also exhibit potential anti-tumor activity. Most of them are DNA-damaging substances, causing relatively strong and selective destruction of tumor cells. We have tested in vitro anti-proliferative effects of newly-synthesized tetrahydroacrid derivatives, namely tacrine-coumarin hybrid molecules, on various human and mouse cancer cell lines. Our results showed that tacrine-coumarin hybrids with seven, eight, and nine methylene groups in spacer reduce proliferation of cancer cells. A hybrid with nine methylene groups had the most significant anti-cancer effect.

Synthesis, in vitro acetylcholinesterase inhibitory activity and molecular docking of new acridine-coumarin hybrids.

A novel series of acridine-coumarin hybrids was synthesized and biologically evaluated for their potential inhibitory effect on both acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE). The newly synthesized derivatives 9a-d have shown higher activity against human AChE (hAChE) compared with 7-MEOTA as the standard drug. Among them derivative 9b exhibited the most potent acetylcholinesterase inhibitory activity, with an IC50 value of 5.85µM compared with 7-MEOTA (IC50=15µM). Molecular modelling studies were performed to predict the binding modes of compounds 9b, 9c and 9f with hAChE/hBuChE.

Targeting copper(II)-induced oxidative stress and the acetylcholinesterase system in Alzheimer's disease using multifunctional tacrine-coumarin hybrid molecules.

Alzheimer's disease is a multifactorial disease that is characterized mainly by Amyloid-ß (A-ß) deposits, cholinergic deficit and extensive metal (copper, iron)-induced oxidative stress. In this work we present details of the synthesis, antioxidant and copper-chelating properties, DNA protection study, cholinergic activity and amyloid-antiaggregation properties of new multifunctional tacrine-7-hydroxycoumarin hybrids. The mode of interaction between copper(II) and hybrids and interestingly, the reduction of Cu(II) to Cu(I) species (for complexes Cu-5e-g) were confirmed by EPR measurements. EPR spin trapping on the model Fenton reaction, using 5,5-dimethyl-1-pyrroline N-oxide (DMPO) as a spin trap, demonstrated a significantly suppressed formation of hydroxyl radicals for the Cu-5e complex in comparison with free copper(II). This suggests that compound 5e upon coordination to free copper ion prevents the Cu(II)-catalyzed decomposition of hydrogen peroxide, which in turn may alleviate oxidative stress-induced damage. Protective activity of hybrids 5c and 5e against DNA damage in a Fenton system (copper catalyzed) was found to be in excellent agreement with the EPR spin trapping study. Compound 5g was the most effective in the inhibition of acetylcholinesterase (hAChE, IC50=38nM) and compound 5b was the most potent inhibitor of butyrylcholinesterase (hBuChE, IC50=63nM). Compound 5c was the strongest inhibitor of A-ß1-40 aggregation, although a significant inhibition (>50%) was detected for compounds 5b, 5d, 5e and 5g. Collectively, these results suggest that the design and investigation of multifunctional agents containing along with the acetylcholinesterase inhibitory segment also an antioxidant moiety capable of alleviating metal (copper)-induced oxidative stress, may be of importance in the treatment of Alzheimer's disease.

Inhibition of DNA topoisomerases I and II and growth inhibition of HL-60 cells by novel acridine-based compounds.

HL-60 cancer cells were treated with a series of novel acridine derivatives (derivatives 1-4) in order to test the compounds' ability to inhibit both cancer cell growth and topoisomerase I and II activity. Binding studies of derivatives 1-4 with calf thymus DNA were also performed using a number of techniques (UV-Vis and fluorescence spectroscopy, thermal denaturation, linear dichroism and viscometry) to determine the nature of the interaction between the compounds and ctDNA. The binding constants for the complexes of the studied acridine derivatives with DNA were calculated from UV-Vis spectroscopic titrations (K=3.1×10(4)-2.0×10(3)M(-1)). Some of the compounds showed a strong inhibitory effect against Topo II at the relatively low concentration of 5µM. Topo I/II inhibition mode assays were also performed and verified that the novel compounds are topoisomerase suppressors rather than poisons. The biological activities of derivatives were studied using MTT assay and flow cytometric methods (detection of mitochondrial membrane potential, measurement of cell viability) after 24 and 48h incubation. The ability of derivatives to impair cell proliferation was tested by an analysis of cell cycle distribution.

Tacrine derivatives as dual topoisomerase I and II catalytic inhibitors.

This study examines the binding properties of a series of newly synthetized tacrine derivatives 1-4 and their anticancer effects. Spectroscopic techniques (UV-Vis, fluorescence spectroscopy, thermal denaturation, and linear spectropolarimetry) and viscometry were used to study DNA binding properties and to determine the types of DNA interaction with the studied derivatives. The binding constants for the complexes with DNA were obtained using UV-Vis spectroscopic titrations (K = 1.6 × 10(4)-4.0 × 10(5) M(-1)) and electrophoretic methods were used to determine the effect of the derivatives on topoisomerase I and II activity. Monotacrine derivative 1 showed evidence of topoisomerase Irelaxation activity at a concentration of 30 × 10(-6) M, while bistacrine derivatives 2-4 produced a complete inhibition of topoisomerase Iat a concentration of 5 × 10(-6) M. The biological activities of the derivatives were studied using MTT-assay and flow cytometric methods (detection of mitochondrial membrane potential and measurement of cell viability) following incubation of 24 and 48 h with human leukemic cancer cell line HL60. The ability of the derivatives to impair cell proliferation was also tested through the analysis of cell cycle distribution.

Synthesis and biological evaluation of novel tacrine derivatives and tacrine-coumarin hybrids as cholinesterase inhibitors.

A series of novel tacrine derivatives and tacrine-coumarin heterodimers were designed, synthesized, and biologically evaluated for their potential inhibitory effect on both acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE). Of these compounds, tacrine-coumarin heterodimer 7c and tacrine derivative 6b were found to be the most potent inhibitors of human AChE (hAChE), demonstrating IC50 values of 0.0154 and 0.0263 µM. Ligands 6b, 6c, and 7c exhibited the highest levels of inhibitory activity against human BuChE (hBuChE), demonstrating IC50 values that range from 0.228 to 0.328 µM. Docking studies were performed in order to predict the binding modes of compounds 6b and 7c with hAChE/hBuChE.

Novel tacrine/acridine anticholinesterase inhibitors with piperazine and thiourea linkers.

A new series of substituted tacrine/acridine and tacrine/tacrine dimers with aliphatic or alkylene-thiourea linkers was synthesized and the potential of these compounds as novel human acetylcholinesterase (hAChE) and human butyrylcholinesterase (hBChE) inhibitors with nanomolar inhibition activity was evaluated. The most potent AChE inhibitor was found to be homodimeric tacrine derivative 14a, which demonstrated an IC50 value of 2 nM; this value indicates an activity rate which is 250-times higher than that of tacrine 1 and 7500-times higher than 7-MEOTA 15, the compounds which were used as standards in the study. IC50 values of derivatives 1, 9, 10, 14b and 15 were compared with the dissociation constants of the enzyme-inhibitor complex, Ki1, and the enzyme-substrate-inhibitor complex, Ki2, for. A dual binding site is presumed for the synthesized compounds which possess two tacrines or tacrine and acridine as terminal moieties show evidence of dual site binding. DFT calculations of theoretical desolvation free energies, ΔΔGtheor, and docking studies elucidate these suggestions in more detail.

Synthesis, design and biological evaluation of novel highly potent tacrine congeners for the treatment of Alzheimer's disease.

New tacrine derivatives 5a-d, 6a-d with piperazino-ethyl spacer linked with corresponding secondary amines and tacrine homodimer 8 were synthesized and tested as cholinesterase inhibitors on human acetylcholinesterase (hAChE) and human plasmatic butyrylcholinesterase (hBChE). In most cases the majority of synthesized derivatives exhibit a high AChE and BChE inhibitory activity with IC(50) values in the low-nanomolar range, being clearly more potent than the reference standard tacrine (9-amino-1,2,3,4-tetrahydroacridine, 1) and 7-MEOTA (7-methoxy-9-amino-1,2,3,4-tetrahydroacridine). Among them, inhibitors 8 and 5c, showed a strong inhibitory activity against hAChE, with an IC(50) value of 4.49 nM and 4.97, nM resp., and a high selectivity to hAChE. The compound 5d acted as the most potent inhibitor against hBChE with an IC(50) value of 33.7 nM and exhibited also a good selectivity towards hBChE. The dissociation constants K(i) of the selected inhibitors were compared with their IC(50) values. Molecular modeling studies were performed to predict the binding modes between individual derivatives and hAChE/hBChE.