Quinones bearing non-steroidal anti-inflammatory fragments as multitarget ligands for Alzheimer’s disease

Computational evaluation of quinones of Nigella sativa L. as potential inhibitor of dengue virus NS5 methyltransferase

Aedes aegypti is the primary vector for the transmission of the dengue virus, which causes dengue fever, dengue hemorrhagic illness and dengue shock syndrome. There is now no antiviral medication available to treat DENV, which kills thousands of people each year and infects millions of individuals. A possible target for the creation of fresh and efficient dengue treatments is the DENV-3 NS5 MTase. So, Nigella sativa quinones were examined using in silico methods to find natural anti-DENV compounds. The in silico docking was conducted utilising the Discovery Studio software on the quinones of N. sativa and the active site of the target protein DENV-3 NS5 MTase. In addition, the druggability and pharmacokinetics of the lead compound were assessed. Dithymoquinone was comparable to the reference compound in terms of its ability to bind to the active site of target protein. Dithymoquinone met the requirements for drug likeness and Lipinski's principles, as demonstrated by the ADMET analysis and drug likeness results. The current study indicated that the dithymoquinone from N. sativa had anti-DENV activity, suggesting further drug development and dengue treatment optimisation.Communicated by Ramaswamy H. Sarma.

Quinones as Neuroprotective Agents

Quinones can in principle be viewed as a double-edged sword in the treatment of neurodegenerative diseases, since they are often cytoprotective but can also be cytotoxic due to covalent and redox modification of biomolecules. Nevertheless, low doses of moderately electrophilic quinones are generally cytoprotective, mainly due to their ability to activate the Keap1/Nrf2 pathway and thus induce the expression of detoxifying enzymes. Some natural quinones have relevant roles in important physiological processes. One of them is coenzyme Q₁₀, which takes part in the oxidative phosphorylation processes involved in cell energy production, as a proton and electron carrier in the mitochondrial respiratory chain, and shows neuroprotective effects relevant to Alzheimer's and Parkinson's diseases. Additional neuroprotective quinones that can be regarded as coenzyme Q₁₀ analogues are idobenone, mitoquinone and plastoquinone. Other endogenous quinones with neuroprotective activities include tocopherol-derived quinones, most notably vatiquinone, and vitamin K. A final group of non-endogenous quinones with neuroprotective activity is discussed, comprising embelin, APX-3330, cannabinoid-derived quinones, asterriquinones and other indolylquinones, pyrroloquinolinequinone and its analogues, geldanamycin and its analogues, rifampicin quinone, memoquin and a number of hybrid structures combining quinones with amino acids, cholinesterase inhibitors and non-steroidal anti-inflammatory drugs.

Systematic In Silico Design, Synthesis, and Biological Studies of Some Novel 1,4-Benzoquinone Derivatives for the Prospective Management of Cognitive Decline

Cholinesterases are significant biological targets for the regulation of cholinergic neurotransmission, and their inhibitors are being exploited for the management of cognitive decline in various neurological conditions. The 1,4-benzoquinone scaffold possesses antioxidant potential along with AChE inhibition activity in various neurological disorders. To design novel and potent selective 1,4-benzoquinone analogues as cholinesterase inhibitors, a ligand-based drug design strategy was followed to develop a 3D quantitative structure-selectivity relationship (QSSR) model. On the basis of the best fit model, eight novel 1,4-benzoquinone derivatives were designed and synthesized implementing appropriate synthetic procedures and were characterized by various spectral and elemental techniques. All the synthesized compounds were evaluated for their selective in vitro acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) inhibitory potential at different concentrations using mice brain homogenate as the source of the enzyme. Out of these compounds, the three most selective compounds were further evaluated for behavioral variations using step down passive avoidance and escape learning procedure at a dose of 0.5 mg/kg taking donepezil as the reference drug. Biochemical estimation of the markers of oxidative stress (lipid peroxidation, superoxide dismutase, glutathione, and catalase) has also been carried out to determine the role of the synthesized molecules on the scopolamine induced oxidative damage. Compound 2a displayed appreciable selectivity index values as predicted through the 3D-QSSR model. Further, docked complexes of compound 2a with AChE and BChE were subjected to molecular dynamic simulations for a period of 30 ns to study the orientations and stable conformations of the most active molecules in the catalytic domain of these enzymes. The results obtained from the 3D-QSSR analysis, docking, and molecular dynamic studies were found to be appreciable and provided a deep insight into the structural features required for the selectivity of AChE inhibitors over BChE. The outcome of this study may be used as a novel tool to design new highly selective and more potent molecules.

Triphenylantimony(V) Catecholates of the Type (3-RS-4,6-DBCat)SbPh3-Catechol Thioether Derivatives: Structure, Electrochemical Properties, and Antiradical Activity

A new series of triphenylantimony(V) 3-alkylthio/arylthio-substituted 4,6-di-tert-butylcatecholates of the type (3-RS-4,6-DBCat)SbPh3, where R = n-butyl (1), n-hexyl (2), n-octyl (3), cyclopentyl (4), cyclohexyl (5), benzyl (6), phenyl (7), and naphthyl-2 (8), were synthesized from the corresponding catechol thioethers and Ph3SbBr2 in the presence of a base. The crystal structures of 1, 2, 3, and 5 were determined by single-crystal X-ray analysis. The coordination polyhedron of 1-3 is better described as a tetragonal pyramid with a different degree of distortion, while that for 5- was a distorted trigonal bipyramid (τ = 0.014, 0.177, 0.26, 0.56, respectively). Complexes demonstrated different crystal packing of molecules. The electrochemical oxidation of the complexes involved the catecholate group as well as the thioether linker. The introduction of a thioether fragment into the aromatic ring of catechol ligand led to a shift in the potential of the "catechol/o-semiquinone" redox transition to the anodic region, which indicated the electron-withdrawing nature of the RS group. The radical scavenging activity of the complexes was determined in the reaction with DPPH radical.

New hybrids of tacrine and indomethacin as multifunctional acetylcholinesterase inhibitors

A new series of hybrid compounds were designed, consisting of anti-AChE and BuChE activity components with an anti-inflammatory component. A series of 9-amino-1,2,3,4-tetrahydroacridine and indomethacin derivatives were synthesized. All compounds were created using alkyldiamine with different chain lengths as a linker. Various biological activities were evaluated, including inhibitory activity against AChE and BuChE. The tested compounds showed high inhibitory activities against cholinesterases. The IC50 values for all compounds ranging from 10 nM to 7 µM. The potency of inhibition was much higher than well-known AChE and BuChE inhibitors (tacrine and donepezil). Compound 3h had the strongest inhibitory activity; kinetic studies showed it to have a mixed-type of acetylcholinesterase inhibition properties. The cytotoxicity of the newly-synthesized compounds against HepG2 (hepatocarcinoma cells) and EA.hy96 (human vein endothelial cells) cell lines was determined using the MTT and MTS tests. All investigated compounds presented similar cytotoxic activity against HepG2 and EA.hy926 cell line, ranged in micromolar values. Compounds with longer linkers showed higher antioxidant activity. The most active compound was 3h. Docking studies confirmed interactions with important regions of AChE and BuChE. Its multifunctional properties, i.e. high activity against AChE and BuChE, antioxidant activity and low cytotoxicity, highlight 3h as a promising agent for the treatment of AD.

Effect of DPP-4 inhibitor on elderly patients with T2DM combined with MCI

The aim of this study was to investigate the effect of dipeptidyl peptidase-4 (DPP-4) inhibitor on blood sugar level and cognitive ability in elderly patients with type 2 diabetes mellitus (T2DM) combined with post-stroke mild cognitive impairment (MCI). Thirty patients received DPP-4 inhibitor (study group), while another thirty received sulfonylurea (control group). Six months after treatment, markers regarding blood sugar were improved in both groups (all P<0.05) without intergroup differences (all P>0.05); scores regarding cognitive ability improved in the study group (both P<0.05) and were higher versus the control group (both P<0.01); the study group had higher Aβ1-42/Aβ1-40 value versus the pretreatment value (P<0.001), which differed from the control group (P<0.05); tumor necrosis factor-α and interleukin-6 concentrations decreased in both groups, while the study group had greater reductions; C-reactive protein value decreased after treatment in the study group (all P<0.05). Using DPP-4 inhibitor in elderly patients with T2DM combined with post-stroke MCI can lower blood sugar and improve cognitive ability. The mechanism may be associated with the improvement of Aβ gathering and reduction in inflammatory response.

1,8-Substituted anthraquinones, anthrones and bianthrones as potential non-azole leads against fungal infections

The synthesis of a variety of 1,8-substituted anthraquinones, anthrones and bianthrones and their potential as antifungal agents is evaluated. Preliminary screening against Schizosaccharomyces pombe (S. pombe), a fission yeast, and Saccharomyces cerevisiae (S. cerevisiae), a budding yeast, is reported. Both these yeast species demonstrate close homologue to a number of pathogenic fungi.

Silymarin's Inhibition and Treatment Effects for Alzheimer's Disease

As a longstanding problem, Alzheimer's disease (AD) has stymied researchers in the medical field with its increasing incidence and enormous treatment difficulty. Silymarin has always been valued by researchers for its good efficacy and safety in treating liver disease. Recent studies have shown that silymarin also has good pharmacological activity in the nervous system, especially for the treatment of AD. Silymarin can control the production of Aβ by inhibiting the precursor substance of Aβ (β-amyloid precursor protein), and it can inhibit the polymerization of Aβ. Silymarin can also increase the acetylcholine content in the nervous system by inhibiting cholinesterase activity. At the same time, it also has the effect of resisting oxidative stress and the inflammatory response of the nervous system. These pharmacological activities contribute to the inhibition of the onset of AD. The good efficacy of silymarin on AD and its high safety and availability give it huge potential for the treatment of AD.

Identification of novel acetylcholinesterase inhibitors designed by pharmacophore-based virtual screening, molecular docking and bioassay

In this study, pharmacophore based 3D QSAR models for human acetylcholinesterase (AChE) inhibitors were generated, with good significance, statistical values (r2training = 0.73) and predictability (q2training = 0.67). It was further validated by three methods (Fischer's test, decoy set and Güner-Henry scoring method) to show that the models can be used to predict the biological activities of compounds without costly and time-consuming synthesis. The criteria for virtual screening were also validated by testing the selective AChE inhibitors. Virtual screening experiments and subsequent in vitro evaluation of promising hits revealed a novel and selective AChE inhibitor. Thus, the findings reported herein may provide a new strategy for the discovery of selective AChE inhibitors. The IC50 value of compounds 5c and 6a presented selective inhibition of AChE without inhibiting butyrylcholinesterase (BChE) at uM level. Molecular docking studies were performed to explain the potent AChE inhibition of the target compounds studies to explain high affinity.

New pyridine derivatives as inhibitors of acetylcholinesterase and amyloid aggregation

A new series of pyridine derivatives with carbamic or amidic function has been designed and synthesized to act as cholinesterase inhibitors. The synthesized compounds were tested toward EeAChE and hAChE and toward eqBChE and hBChE. The carbamate 8 was the most potent hAChE inhibitor (IC₅₀ = 0.153 ± 0.016 μM) while the carbamate 11 was the most potent inhibitor of hBChE (IC₅₀ = 0.828 ± 0.067 μM). A molecular docking study indicated that the carbamate 8 was able to bind AChE by interacting with both CAS and PAS, in agreement with the mixed inhibition mechanism. Furthermore, the carbamates 8, 9 and 11 were able to inhibit Aβ₄₂ self-aggregation and possessed quite low toxicity against human astrocytoma T67 and HeLa cell lines, being the carbamate 8 the less toxic compound on both cell lines.

Alzheimer's disease in people with Down's syndrome: the prospects for and the challenges of developing preventative treatments

People with Down's syndrome (DS) are at high risk for developing Alzheimer's disease (AD) at a relatively young age. This increased risk is not observed in people with intellectual disabilities for reasons other than DS and for this reason it is unlikely to be due to non-specific effects of having a neurodevelopmental disorder but, instead, a direct consequence of the genetics of DS (trisomy 21). Given the location of the amyloid precursor protein (APP) gene on chromosome 21, the amyloid cascade hypothesis is the dominant theory accounting for this risk, with other genetic and environmental factors modifying the age of onset and the course of the disease. Several potential therapies targeting the amyloid pathway and aiming to modify the course of AD are currently being investigated, which may also be useful for treating AD in DS. However, given that the neuropathology associated with AD starts many years before dementia manifests, any preventative treatment must start well before the onset of symptoms. To enable trials of such interventions, plasma, CSF, brain, and retinal biomarkers are being studied as proxy early diagnostic and outcome measures for AD. In this systematic review, we consider the prospects for the development of potential preventative treatments of AD in the DS population and their evaluation.

Synthesis and antitumor activity of selenium-containing quinone-based triazoles possessing two redox centres, and their mechanistic insights

Selenium-containing quinone-based 1,2,3-triazoles were synthesized using click chemistry, the copper catalyzed azide-alkyne 1,3-dipolar cycloaddition, and evaluated against six types of cancer cell lines: HL-60 (human promyelocytic leukemia cells), HCT-116 (human colon carcinoma cells), PC3 (human prostate cells), SF295 (human glioblastoma cells), MDA-MB-435 (melanoma cells) and OVCAR-8 (human ovarian carcinoma cells). Some compounds showed IC50 values < 0.3 μM. The cytotoxic potential of the quinones evaluated was also assayed using non-tumor cells, exemplified by peripheral blood mononuclear (PBMC), V79 and L929 cells. Mechanistic role for

NAD(P)H

Quinone Oxidoreductase 1 (NQO1) was also elucidated. These compounds could provide promising new lead derivatives for more potent anticancer drug development and delivery, and represent one of the most active classes of lapachones reported.

Acetylcholinesterase inhibitory activity of pigment echinochrome A from sea urchin Scaphechinus mirabilis

Echinochrome A (EchA) is a dark-red pigment of the polyhydroxynaphthoquinone class isolated from sea urchin Scaphechinus mirabilis. Acetylcholinesterase (AChE) inhibitors are used in the treatment of various neuromuscular disorders, and are considered as strong therapeutic agents for the treatment of Alzheimer's disease (AD). Although EchA is clinically used to treat ophthalmic diseases and limit infarct formation during ischemia/ reperfusion injury, anti-AChE effect of EchA is still unknown. In this study, we investigated the anti-AChE effect of EchA in vitro. EchA and its exhausted form which lost anti-oxidant capacity did not show any significant cytotoxicy on the H9c2 and A7r5 cells. EchA inhibited AChE with an irreversible and uncompetitive mode. In addition, EchA showed reactive oxygen species scavenging activity, particularly with nitric oxide. These findings indicate new therapeutic potential for EchA in treating reduced acetylcholine-related diseases including AD and provide an insight into developing new AChE inhibitors.

Two diseases, one approach: multitarget drug discovery in Alzheimer's and neglected tropical diseases

Multitarget drug discovery may represent a promising therapeutic approach to treat Alzheimer's and neglected tropical diseases.