Pharmacological Evaluation and Docking Studies of 3-Thiadiazolyl- and Thioxo-1,2,4-triazolylcoumarin Derivatives as Cholinesterase Inhibitors

Thiadiazole – A promising structure in design and development of anti-Alzheimer agents

The design and development of effective multitargeted agents in treating Alzheimer disease (AD) has always been a hot topic in the field of drug discovery. Since AD is a multifactorial disorder, various key hidden players such as deficit of acetylcholine (ACh), tau-protein aggregation, and oxidative stress have been associated with the incidence and progress of AD. In pursuit of improving efficacy and expanding the range of pharmacological activities of current AD drugs, the molecular hybridization method is also used intensively. Five-membered heterocyclic systems such as thiadiazole scaffolds have previously been shown to have therapeutic activity. Thiadiazole analogs as an anti-oxidant compound have been known to include a wide range of biological activity from anti-cancer to anti-Alzheimer properties. The suitable pharmacokinetic and physicochemical properties of the thiadiazole scaffold have introduced it as a therapeutic target in medicinal chemistry. The current review portrays the critical role of the thiadiazole scaffold in the design of various compounds with potential effects in the treatment of Alzheimer's disease. Furthermore, the rationale used behind hybrid-based design strategies and the outcomes achieved through the hybridization of Thiadiazole analogs with various core structures have been discussed. In addition, the data in the present review may help researchers in the design of new multidrug combinations that may provide new options for the treatment of AD.

Coumarin-acetohydrazide derivatives as novel antiproliferative agents via VEGFR-2/AKT axis inhibition and apoptosis triggering

The VEGFR-2/AKT pathway is a crucial axis in tumor survival where it is highly dysregulated in many cancer types.

Design, synthesis and biological evaluation of substituted pyrazoles endowed with brominated 4-methyl 7-hydroxy coumarin as new scaffolds against Alzheimer’s disease

Background

The study aimed to design, synthesize and evaluate various brominated derivatives of 7-hydroxy coumarin as a new scaffold against Alzheimer’s disease by in vivo and in vitro models. A group of three novel pyrazoles endowed with brominated 7-hydroxy 4-methyl coumarin derivatives were designed. Among the designed compounds, a single entity (D1) was selected based on the docking score, which could be considered mainly for the treatment of Alzheimer’s disease. Three novel pyrazoles endowed with brominated 7-hydroxy 4-methyl coumarin derivatives were designed and docking studies of these compounds were carried out using Argus lab4.0.1 version. According to the docking score, a single entity of compound (D1) was selected for further study. The structure of the compound (D1) was explored by spectral analysis. The anti-Alzheimer’s activity was evaluated by in vivo and in vitro methods. All results were compared statistically by one-way ANOVA using GraphPad Prism.

Results

Molecular docking studies revealed that the compound D1 was able to bind simultaneously to the amino acid and in the active sites of the acetylcholine esterase enzyme. In acetylcholine esterase inhibition assay, the compound shows a significant increase in acetylcholine esterase level. The MAO inhibitory activities were in the nanomole range (human MAO-A IC50 = 3.9, human MAO-B IC 50 = 4.4). DPPH (2,2-diphenyl-1-picryl-hydrazyl-hydrate) assay showed that the compound shows a promising antioxidant property. In the evaluation of learning and memory of compound D1 using elevated plus maze, the compound D1-pretreated group showed a significant increase in memory and learning when compared with donepezil.

Conclusions

Among the designed series of pyrazole endowed with brominated 7-hydroxyl 4-methyl coumarin derivatives, compound D1 showed good antioxidant property and acetylcholine esterase and MAO inhibitory activity; based on this property, the synthesized compound D1 can be considered a new scaffold on Alzheimer’s disease.

In vitro antimicrobial evaluation and in silico studies of coumarin derivatives tagged with pyrano-pyridine and pyrano-pyrimidine moieties as DNA gyrase inhibitors

Several coumarin-containing substitute nitrogen heterocycles have recently received considerable importance due to their diverse pharmacological properties. One-pot and rapid synthesis of coumarin derivatives was achieved via reactions of acetyl-coumarin with p-chloro-benzaldehyde and malononitrile to provide compound 2-containing cyano-amine using conventional heating. Compound 2 was condensed with different carbon electrophiles triethyl orthoformate, phenyl isocyanate, carbon disulfide, benzoyl chloride, and acetyl chloride that afforded the corresponding chromene derivatives 3-17. All the newly synthesized compounds were characterized by elemental and spectroscopic evidences. All of the synthesized compounds were tested for antimicrobial activity against S. Pneumoniae, S. Epidermidis, S. Aureus, and E. coli as Gram + ve Bacteria, K. Pneumoniae, S. Paratyphi as Gram -ve Bacteria, P. Italicum, A. Fumigatus representative for Fungi. The preliminary screening results showed that most of the compounds had moderate to high activity against all tested organisms. The most potent four compounds were subjected to further investigation against E. Coli DNA gyrase and topoisomerase IV inhibitory activity, and the results showed that all of these derivatives inhibit DNA gyrase and thus cell division. Also, in silico studies were done for the most active compounds which showed good results.

Alkynoates as Versatile and Powerful Chemical Tools for the Rapid Assembly of Diverse Heterocycles under Transition-Metal Catalysis: Recent Developments and Challenges

Heterocycles, heteroaromatics and spirocyclic entities are ubiquitous components of a wide plethora of synthetic drugs, biologically active natural products, marketed pharmaceuticals and agrochemical targets. Recognizing their high proportion in drugs and rich pharmacological potential, these invaluable structural motifs have garnered significant interest, thus enabling the development of efficient catalytic methodologies providing access to architecturally complex and diverse molecules with high atom-economy and low cost. These chemical processes not only allow the formation of diverse heterocycles but also utilize a range of flexible and easily accessible building units in a single operation to discover diversity-oriented synthetic approaches. Alkynoates are significantly important, diverse and powerful building blocks in organic chemistry due to their unique and inherent properties such as the electronic bias on carbon-carbon triple bonds posed by electron-withdrawing groups or the metallic coordination site provided by carbonyl groups. The present review highlights the comprehensive picture of the utility of alkynoates (2007-2019) for the synthesis of various heterocycles (> 50 types) using transition-metal catalysts (Ru, Rh, Pd, Ir, Ag, Au, Pt, Cu, Mn, Fe) in various forms. The valuable function of versatile alkynoates (bearing multifunctional groups) as simple and useful starting materials is explored, thus cyclizing with an array of coupling partners to deliver a broad range of oxygen-, nitrogen-, sulfur-containing heterocycles alongside fused-, and spiro-heterocyclic compounds. In addition, these examples will also focus the scope and reaction limitations, as well as mechanistic investigations into the synthesis of these heterocycles. The biological significance will also be discussed, citing relevant examples of drug molecules highlighting each class of heterocycles. This review summarizes the recent developments in the synthetic methods for the synthesis of various heterocycles using alkynoates as readily available starting materials under transition-metal catalysis.

Discovery of Novel Coumarin Analogs against the α-Glucosidase Protein Target of Diabetes Mellitus: Pharmacophore-Based QSAR, Docking, and Molecular Dynamics Simulation Studies

Diabetes mellitus (DM) is a chronic metabolic disease, the third killer of mankind. The finding of potent drugs against diabetes remains challenging. In the present study, coumarin derivatives with known biological activity against diabetic protein have been used to predict functional groups' positions on coumarin derivatives. α-Glucosidase is a brush border membrane-bound lysosomal enzyme from the hydrolase enzyme family. It plays an important role in the metabolism of glycoproteins. Inhibitors of lysosomal α-glucosidase can reduce postprandial hyperglycemia. Due to this, lysosomal α-glucosidase is a good therapeutic target for drugs. A total of 116 coumarin derivatives with IC50 values against lysosomal α-glucosidase were selected for a CADD (computer-aided drug design) approach to identify more potent drugs. Pharmacophore modeling and atom-based 3-QSAR of 116 active compounds against lysosomal α-glucosidase were performed and identified positions and types of groups to increase activity. We performed molecular docking of 116 coumarin derivatives against the lysosomal α-glucosidase enzyme, and three compounds (isorutarine, 10_, and 36) resulted in a docking score of -7.64, -7.12, and -6.86 kcal/mol. The molecular dynamics simulation of the above three molecules and protein complex performed for 100 ns supported the interaction stability of isorutarine, 10_, and 36 with the lysosomal binding site α-glucosidase.

Rational approaches, design strategies, structure activity relationship and mechanistic insights for therapeutic coumarin hybrids

Hybrid molecules, furnished by combining two or more pharmacophores is an emerging concept in the field of medicinal chemistry and drug discovery that has attracted substantial traction in the past few years. Naturally occurring scaffolds such as coumarins display a wide spectrum of pharmacological activities including anticancer, antibiotic, antidiabetic and others, by acting on multiple targets. In this view, various coumarin-based hybrids possessing diverse medicinal attributes were synthesized in the last five years by conjugating coumarin moiety with other therapeutic pharmacophores. The current review summarizes the recent development (2014 and onwards) of these pharmacologically active coumarin hybrids and demonstrates rationale behind their design, structure-activity relationships (SAR) and mechanistic studies performed on these hybrid molecules. This review will be beneficial for medicinal chemist and chemical biologist, and in general to the drug discovery community and will facilitate the synthesis and development of novel, potent coumarin hybrid molecules serving as lead molecules for the treatment of complex disorders.

Facile and expedient access to bis-coumarin–iminothiazole hybrids by molecular hybridization approach: synthesis, molecular modelling and assessment of alkaline phosphatase inhibition, anticancer and antileishmanial potential

A series of new cytotoxic bis-coumarin–iminothiazole hybrids was developed as potential inhibitors of alkaline phosphatase and leishmaniasis.

Chemical constituents antioxidant and anticholinesterasic activity of Tabernaemontana catharinensis

The present work aimed to analyze the alkaloid content of the ethanolic extract of Tabernaemontana catharinensis (Apocynaceae family) and its fractions as well as to evaluate their antioxidant and anticholinesterasic activities. The analyses of the ethanolic extract of T. catharinensis by mass spectrometry allowed identifying the presence of the alkaloids 16-epi-affinine, coronaridine-hydroxyindolenine, voachalotine, voacristine-hydroxyindolenine, and 12-methoxy-n-methyl-voachalotine, as well as an alkaloid with m/z 385.21 whose spectrum suggests a derivative of voacristine or voacangine. The extract and its alkaloid rich fractions showed antioxidant activity, especially those that contain the alkaloid m/z 385.21 or 16-epi-affinine with DPPH scavenging activity (IC₅₀) between 37.18 and 74.69 μg/mL. Moreover, the extract and its fractions exhibited anticholinesterasic activity, particularly the fractions characterized by the presence of 12-methoxy-n-methyl-voachalotine, with IC₅₀ = 2.1 to 2.5 μg/mL. Fractions with 16-epi-affinine combined good antioxidant (IC₅₀ = 65.59 to 74.69 μg/mL) and anticholinesterasic (IC₅₀ = 7.7 to 8.3 μg/mL) activities, representing an option for further studies aimed at treating neurodegenerative diseases.