Ferrocene modified analogues of imatinib and nilotinib as potent anti-cancer agents.

The unique features of ferrocene and the need for development of targeted anticancer drugs inspired the design, synthesis and biological evaluation of ferrocenyl modified tyrosine kinase inhibitors by replacing the pyridyl moiety in imatinib and nilotinib generalized structures with a ferrocenyl group. A series of seven new ferrocene analogues were synthesized and evaluated for their anticancer activity in a panel of bcr-abl positive human malignant cell lines using imatinib as a reference drug. The metallocenes exhibited a dose-dependent inhibition on malignant cell growth with varying antileukemic activity. The most potent analogues were compounds 9 and 15a showing comparable or even superior efficacy to the reference. Their cancer selectivity indices suggest a favorable selectivity profile, indicating a 250 times higher preferential activity of 15a towards malignantly transformed K-562 cells and an even twice greater one (500) of 9 in the LAMA-84 leukemic model as compared to the normal murine fibroblast cell line.

Ex Vivo Antioxidant and Cholinesterase Inhibiting Effects of a Novel Galantamine-Curcumin Hybrid on Scopolamine-Induced Neurotoxicity in Mice.

Oxidative stress is an essential factor in the development and progression of Alzheimer's disease (AD). An excessive amount of reactive oxygen species (ROS) induces the peroxidation of lipid membranes, reduces the activity of antioxidant enzymes and causes neurotoxicity. In this study, we investigated the antioxidant and cholinesterase inhibitory potential of a novel galantamine-curcumin hybrid, named 4b, administered orally in two doses (2.5 mg/kg and 5 mg/kg) in scopolamine (SC)-induced neurotoxicity in mice. To evaluate the effects of 4b, we used galantamine (GAL) (3 mg/kg) and curcumin (CCN) (25 mg/kg) as positive controls. Ex vivo experiments on mouse brains showed that the higher dose of 4b (5 mg/kg) increased reduced glutathione (GSH) levels by 46%, catalase (CAT) and superoxide dismutase (SOD) activity by 57%, and glutathione peroxidase (GPx) activity by 108%, compared with the SC-treated group. At the same time, 4b (5 mg/kg) significantly reduced the brain malondialdehyde (MDA) level by 31% and acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) activities by 40% and 30%, respectively, relative to the SC-impaired group. The results showed that 4b acted as an antioxidant agent and brain protector, making it promising for further experimental research in the field of neurodegenerative diseases.

A Galantamine-Curcumin Hybrid Decreases the Cytotoxicity of Amyloid-Beta Peptide on SH-SY5Y Cells.

Misfolded amyloid beta (Aß) peptides aggregate and form neurotoxic oligomers. Membrane and mitochondrial damages, calcium dysregulation, oxidative stress, and fibril deposits are among the possible mechanisms of Aß cytotoxicity. Galantamine (GAL) prevents apoptosis induced by Aß mainly through the ability to stimulate allosterically the α7 nAChRs and to regulate the calcium cytosolic concentration. Here, we examined the cytoprotective effects of two GAL derivatives, namely compounds 4b and 8, against Aß cytotoxicity on the human neuroblastoma cell line SH-SY5Y. The protective effects were tested at simultaneous administration, pre-incubation and post-incubation, with Aß. GAL and curcumin (CU) were used in the study as reference compounds. It was found that 4b protects cells in a similar mode as GAL, while compound 8 and CU potentiate the toxic effects of Aß. Allosteric stimulation of α7 nAChRs is suggested as a possible mechanism of the cytoprotectivity of 4b. These and previous findings characterize 4b as a prospective non-toxic multi-target agent against neurodegenerative disorders with inhibitory activity on acetylcholinesterase, antioxidant, and cytoprotective properties.

A Novel Galantamine-Curcumin Hybrid as a Potential Multi-Target Agent against Neurodegenerative Disorders.

The acetylcholinesterase (AChE) inhibitors are the main drugs for symptomatic treatment of neurodegenerative disorders like Alzheimer's disease. A recently designed, synthesized and tested hybrid compound between the AChE inhibitor galantamine (GAL) and the antioxidant polyphenol curcumin (CU) showed high AChE inhibition in vitro. Here, we describe tests for acute and short-term toxicity in mice as well as antioxidant tests on brain homogenates measured the levels of malondialdehide (MDA) and glutathione (GSH) and in vitro DPPH, ABTS, FRAP and LPO inhibition assays. Hematological and serum biochemical analyses were also performed. In the acute toxicity tests, the novel AChE inhibitor given orally in mice showed LD50 of 49 mg/kg. The short-term administration of 2.5 and 5 mg/kg did not show toxicity. In the ex vivo tests, the GAL-CU hybrid performed better than GAL and CU themselves; in a dose of 5 mg/kg, it demonstrates 25% reduction in AChE activity, as well as a 28% and 73% increase in the levels of MDA and GSH, respectively. No significant changes in blood biochemical data were observed. The antioxidant activity of 4b measured ex vivo was proven in the in vitro tests. In the ABTS assay, 4b showed radical scavenging activity 10 times higher than the positive control butylhydroxy toluol (BHT). The GAL-CU hybrid is a novel non-toxic AChE inhibitor with high antioxidant activity which makes it a prospective multitarget drug candidate for treatment of neurodegenerative disorders.

Discovery of a Novel Acetylcholinesterase Inhibitor by Fragment-Based Design and Virtual Screening.

Despite extensive and intensive research efforts in recent decades, there is still no effective treatment for neurodegenerative diseases. On this background, the use of drugs inhibiting the enzyme acetylcholinesterase (AChE) remains an eternal evergreen in the symptomatic treatment of mild to moderate cognitive impairments. Even more, the cholinergic hypothesis, somewhat forgotten in recent years due to the shift in focus on amyloid cascade, is back to life, and the search for new, more effective AChE inhibitors continues. We generated a fragment-based library containing aromatic moieties and linkers originating from a set of novel AChE inhibitors. We used this library to design 1220 galantamine (GAL) derivatives following the model GAL (binding core) - linker (L) - aromatic fragment (Ar). The newly designed compounds were screened virtually for blood-brain barrier (BBB) permeability and binding to AChE. Among the top 10 best-scored compounds, a representative lead molecule was selected and tested for anti-AChE activity and neurotoxicity. It was found that the selected compound was a powerful non-toxic AChE inhibitor, 68 times more active than GAL, and could serve as a lead molecule for further optimization and development.

Binding Expedient of 2-carbamido-1,3-indandione to Nucleic Acids: Potential Fluorescent Probe.

Fluorescent and computational methods were used to elucidate the binding expedient of 2-carbamido-1,3-indandione (CAID) tautomers to nucleotides. The dependence of the fluorescence emission of CAID loaded nucleic acids sequences to compound concentration, temperature and time variation was investigated. It was found that the subject compound binds to nucleic acids but does not intercalate. According to our quantum-chemical calculations on the conjugation between CAID and nucleotides, the binding in the formed complexes may be through hydrogen bonds. Two possible types of complexes were considered-CAID to the phosphate group and CAID to the nucleobase. To estimate the binding affinity, the interaction energies of the formed complexes were calculated. Tautomer 2-carboamide-1-hydroxy-3-oxo-indane is preferred in the formation of complexes, and the phosphate group complexes were more stable. Generally, the guanosine and deoxyguanosine monophosphate complexes were the most preferred regardless of the complex type. Because of the lack of cytotoxic effect on untransformed cell lines of mouse embryo fibroblasts Balb/c 3T3 according to our previous report (Markova et al, (2017) Bulg Chem Commun, 49D, 221-226) and the affinity to nucleic acids, we can suggest that the subject compound could be suitable to be used as a novel type of fluorescent biomarker.

Biological activity of quinazoline analogues and molecular modeling of their interactions with G-quadruplexes.

BACKGROUND: Quinazolines 1 to 6, with an aromatic or aryl-vinyl substituent in position 2 are selected with the aim to compare their structures and biological activity. The selection includes a natural alkaloid, schizocommunin, and the synthetic 2-(2'-quinolyl)-3H-quinazolin-4-one, known to interact with guanine-quadruplex dependent enzymes, respectively telomerase and topoisomerase. METHODS: Breast cancer cells of the MDA cell line have been used to study the bioactivity of the tested compounds by the method of Comet Assay and FACS analyses. We model observed effects assuming stacking interactions of studied heterocycles with a naked skeleton of G-quadruplex, consisting of guanine quartet layers and potassium ions. Interaction energies are computed using a dispersion corrected density functional theory method, and an electron-correlated molecular orbital theory method. RESULTS: Selected compounds do not remarkably delay nor change the dynamics of cellular progression through the cell cycle phases, while changing significantly cell morphology. Our computational models quantify structural effects on heterocyclic G4-complex stabilization energies, which directly correlate with observed biological activity. CONCLUSION: Our computational model of G-quadruplexes is an acceptable tool for the study of interaction energies of G-quadruplexes and heterocyclic ligands, predicting, and allowing design of novel structures. GENERAL SIGNIFICANCE: Genotoxicity of quinazolin-4-one analogues on human breast cancer cells is not related to molecular metabolism but rather to their interference with G-quadruplex regulatory mechanisms. Computed stabilization energies of heterocyclic ligand complexes of G-quadruplexes might be useful in the prediction of novel telomerase / helicase, topoisomerase and NA polymerase dependent drugs.

Galantamine-Curcumin Hybrids as Dual-Site Binding Acetylcholinesterase Inhibitors.

Galantamine (GAL) and curcumin (CU) are alkaloids used to improve symptomatically neurodegenerative conditions like Alzheimer's disease (AD). GAL acts mainly as an inhibitor of the enzyme acetylcholinesterase (AChE). CU binds to amyloid-beta (Aß) oligomers and inhibits the formation of Aß plaques. Here, we combine GAL core with CU fragments and design a combinatorial library of GAL-CU hybrids as dual-site binding AChE inhibitors. The designed hybrids are screened for optimal ADME properties and BBB permeability and docked on AChE. The 14 best performing compounds are synthesized and tested in vitro for neurotoxicity and anti-AChE activity. Five of them are less toxic than GAL and CU and show activities between 41 and 186 times higher than GAL.

Novel hits for acetylcholinesterase inhibition derived by docking-based screening on ZINC database.

The inhibition of the enzyme acetylcholinesterase (AChE) increases the levels of the neurotransmitter acetylcholine and symptomatically improves the affected cognitive function. In the present study, we searched for novel AChE inhibitors by docking-based virtual screening of the standard lead-like set of ZINC database containing more than 6 million small molecules using GOLD software. The top 10 best-scored hits were tested in vitro for AChE affinity, neurotoxicity, GIT and BBB permeability. The main pharmacokinetic parameters like volume of distribution, free fraction in plasma, total clearance, and half-life were predicted by previously derived models. Nine of the compounds bind to the enzyme with affinities from 0.517 to 0.735 µM, eight of them are non-toxic. All hits permeate GIT and BBB and bind extensively to plasma proteins. Most of them are low-clearance compounds. In total, seven of the 10 hits are promising for further lead optimisation. These are structures with ZINC IDs: 00220177, 44455618, 66142300, 71804814, 72065926, 96007907, and 97159977.

Synthetic piperine amide analogs with antimycobacterial activity.

Piperine amide analogs are synthesized by replacement of the piperidine moiety with different types of cyclic amines, including adamantyl and monoterpene-derived fragments. The compounds are screened for activity against Mycobacterium tuberculosis H37Rv. The most potent compounds are the 1-adamantyl and the monoterpene-derived hybrids, which combine nanomolar antimycobacterial activity with low cytotoxicity against human cells. The presence of quaternary carbon atom as main structural requirement for anti-TB activity is pointed out by a QSAR study. The most promising compound is the (+)-isopinocampheylamine-derived amide which is characterized with selectivity index of 1387.8.

Docking-based design and synthesis of galantamine-camphane hybrids as inhibitors of acetylcholinesterase.

Galantamine (GAL) as an acetylcholinesterase inhibitor (AChEI) is among the main drugs approved for the treatment of Alzheimer's disease. It fits perfectly into acetylcholinesterase (AChE) binding gorge, but it is too short to fill it. The amyloid beta (Aß) peptide binds in the peripheral anionic site (PAS) at the entrance of the binding gorge of AChE and initiates the formation of amyloid plaques. The blockade of PAS prevents from AChE-induced Aß aggregation. In this study, we describe the design of a series of galantamine-camphane hybrids as AChEIs. Camphane (CAM) is a bulky fragment that disposes well on the wide gorge entrance. The designed hybrids have linkers of different length. They were docked into AChE, and the highest scored compounds were synthesized and tested for AChE inhibitory activity. Some of the novel hybrids showed 191- and 369-fold better inhibition than GAL. The CAM fragment of the best binders fits in the same region, proximal to PAS, where the Ω-loop of Aß binds to AChE. The hybrids cross blood-brain barrier by passive diffusion and are non-neurotoxic at the inhibitory concentrations.

Docking-based Design of Galantamine Derivatives with Dual-site Binding to Acetylcholinesterase.

The enzyme acetylcholinesterase is a key target in the treatment of Alzheimer's disease because of its ability to hydrolyze acetylcholine via the catalytic binding site and to accelerate the aggregation of amyloid-ß peptide via the peripheral anionic site (PAS). Using docking-based predictions, in the present study we design 20 novel galantamine derivatives with alkylamide spacers of different length ending with aromatic fragments. The galantamine moiety blocks the catalytic site, while the terminal aromatic fragments bind in PAS. The best predicted compounds are synthesized and tested for acetylcholinesterase inhibitory activity. The experimental results confirm the predictions and show that the heptylamide spacer is of optimal length to bridge the galantamine moiety bound in the catalytic site and the aromatic fragments interacting with PAS. Among the tested terminal aromatic fragments, the phenethyl substituent is the most suitable for binding in PAS.

Design, Synthesis, and Antimycobacterial Activity of Novel Theophylline-7-Acetic Acid Derivatives With Amino Acid Moieties.

The theophylline-7-acetic acid (7-TAA) scaffold is a promising novel lead compound for antimycobacterial activity. Here, we derive a model for antitubercular activity prediction based on 14 7-TAA derivatives with amino acid moieties and their methyl esters. The model is applied to a combinatorial library, consisting of 40 amino acid and methyl ester derivatives of 7-TAA. The best three predicted compounds are synthesized and tested against Mycobacterium tuberculosis H37Rv. All of them are stable, non-toxic against human cells and show antimycobacterial activity in the nanomolar range being 60 times more active than ethambutol.

Galantamine derivatives with indole moiety: Docking, design, synthesis and acetylcholinesterase inhibitory activity.

The inhibitors of acetylcholinesterase are the main therapy against Alzheimer's disease. Among them, galantamine is the best tolerated and the most prescribed drug. In the present study, 41 galantamine derivatives with known acetylcholinesterase inhibitory activities expressed as IC50 were selected from the literature and docked into a recombinant human acetylcholinesterase by GOLD. A linear relationship between GoldScores and pIC50 values was found and used to design and predict novel galantamine derivatives with indole moiety in the side chain. The four best predicted compounds were synthesized and tested for inhibitory activity. All of them were between 11 and 95 times more active than galantamine. The novel galantamine derivatives with indole moiety have dual site binding to the enzyme--the galantamine moiety binds to the catalytic anionic site and the indole moiety binds to peripheral anionic site. Additionally, the indole moiety of one of the novel inhibitors binds in a region, close to the peripheral anionic site of the enzyme, where the Ω-loop of amyloid beta peptide adheres to acetylcholinesterase. This compound emerges as a promising lead compound for multi-target anti-Alzheimer therapy not only because of the strong inhibitory activity, but also because it is able to block the amyloid beta deposition on acetylcholinesterase.

Design of novel camphane-based derivatives with antimycobacterial activity.

Although tuberculosis (TB) continues to be one of the leading infectious disease killers globally, it is curable and preventable. Despite the existence of safe, well tolerated and effective drugs used in the TB treatment, the interest in new entities, combinations and regimens increases during the last 10 years. Recently, we reported for a new class of anti-TB agents - camphane-based derivatives with nanomolar activity against Mycobacterium tuberculosis strains. The quantitative structure-activity relationship (QSAR) study on 12 compounds revealed several structural requirements for antimycobacterial activity: two hydrogen bond donors, two or three rings and no large branched substituents. Here, we describe the design of a set of nine novel camphane-based derivatives following these requirements. The compounds were synthesized and tested against M. tuberculosis strain H37Rv. Four of them showed activities in the nanomolar range, significantly higher than the activities in the initial set. The QSAR study based on all 21 derivatives pointed to two main structural requirements for anti-TB activity: two hydrogen bond donors and a side chain with aromatic ring.

Synthesis and antimycobacterial activity of novel camphane-based agents.

A series of six new amidoalcohols was designed and synthesized on the base of the camphor scaffold. Natural amino acids were transformed into their α-hydroxy analogues with retention of configuration, and attached to isobornylamine. The compounds were evaluated for their in vitro activity against Mycobacterium tuberculosis H37Rv. Some of the new compounds show 25 times higher activity than the classical anti-TB drug ethambutol. The activity shifts from micromolar to nanomolar inhibitory concentrations depending on the α-hydroxy acid moiety. Two of the most potent compounds exert low level of cytotoxic activity. These camphane-based amido-alcohols present promising potential lead compounds for further elaboration of antimycobacterial agents.

Novel camphane-based anti-tuberculosis agents with nanomolar activity.

A series of new amidoalcohols and amidodiols were designed on the base of the camphor scaffold and evaluated for their in vitro activity against Mycobacterium tuberculosis H37Rv and MDR strain 43. Some of the new compounds show 25 times higher activity than the classical anti-TB drug ethambutol. Small structural changes in the side chain shift the activity from micromolar to nanomolar inhibitory concentrations. Quantitative structure-activity relationship (QSAR) model is derived to guide the further lead optimization. Two hydrogen bond donors and up to three rings in the molecules are optimal for nanomolar activity. The camphane-based amides present novel promising scaffolds for antimycobacterial agents.