Developing hybrid molecule therapeutics for diverse enzyme inhibitory action: Active role of coumarin-based structural leads in drug discovery

Structural modification strategies of triazoles in anticancer drug development

The triazole functional group plays a pivotal role in the composition of biomolecules with potent anticancer activities, including numerous clinically approved drugs. The strategic utilization of the triazole fragment in the rational modification of lead compounds has demonstrated its ability to improve anticancer activities, enhance selectivity, optimize pharmacokinetic properties, and overcome resistance. There has been significant interest in triazole-containing hybrids in recent years due to their remarkable anticancer potential. However, previous reviews on triazoles in cancer treatment have failed to provide tailored design strategies specific to these compounds. Herein, we present an overview of design strategies encompassing a structure-modification approach for incorporating triazoles into hybrid molecules. This review offers valuable references and briefly introduces the synthesis of triazole derivatives, thereby paving the way for further research and advancements in the field of effective and targeted anticancer therapies.

Synthesis, Molecular Electron Density Theory Study, Molecular Docking, and Pharmacological Evaluation of New Coumarin-Sulfonamide-Nitroindazolyl-Triazole Hybrids as Monoamine Oxidase Inhibitors

Inhibitors of monoamine oxidases (MAOs) are of interest for the treatment of neurodegenerative disorders and other human pathologies. In this frame, the present work describes different synthetic strategies to obtain MAO inhibitors via the coupling of the aminocoumarin core with arylsulfonyl chlorides followed by copper azide-alkyne cycloaddition, leading to coumarin-sulfonamide-nitroindazolyl-triazole hybrids. The nitration position on the coumarin moiety was confirmed through nuclear magnetic resonance spectroscopy and molecular electron density theory in order to elucidate the molecular mechanism and selectivity of the electrophilic aromatic substitution reaction. The coumarin derivatives were evaluated for their inhibitory potency against monoamine oxidases and cholinesterases. Molecular docking calculations provided a rational binding mode of the best compounds in the series with MAO A and B. The work identified hybrids 14a-c as novel MAO inhibitors, with a selective action against isoform B, of potential interest to combat neurological diseases.

Antibacterial Activity and Mechanism of Action of Osthole against Listeria monocytogenes

The purpose of this study was to investigate the antibacterial activity and mechanism of action of osthole against Listeria monocytogenes. The antibacterial activity of osthole was evaluated by determining the minimum inhibitory concentration (MIC) and growth curve. Cell morphology, membrane permeability, membrane integrity, bacterial physiology, and metabolism were explored using different methods to elucidate the mechanism of action of osthole. It was shown that the MIC of osthole against L. monocytogenes was 62.5 μg/mL and it inhibited the growth of L. monocytogenes effectively in a concentration-dependent manner. Scanning electron microscopy (SEM) images demonstrated morphology changes of L. monocytogenes, including rough surface, cell shrinkage, and rupture. It was found that extracellular conductivity and macromolecule content were increased significantly in the presence of osthole, indicating the disruption of cell membrane integrity and permeability. Laser confocal microscopy results supported the conclusion that osthole caused severe damage to the cell membrane. It was also noticed that osthole depleted intracellular adenosine triphosphate (ATP), inhibited Na+-K+-ATPase and Ca2+-Mg2+-ATPase activity, and promoted the accumulation of intracellular reactive oxygen species (ROS), leading to cell death. This study suggests that osthole is a promising antibacterial agent candidate against L. monocytogenes, and it shows potential in the prevention and control of foodborne pathogens.

Synthesis of novel coumarin-triazole hybrids and first evaluation of the 4-phenyl substituted hybrid loaded PLGA nanoparticles delivery system to the anticancer activity

Despite the discovery of many chemotherapeutic drugs that prevent uncontrolled cell division processes in the last century, many studies are still being carried out to develop drugs with higher anticancer efficacy and lower level of side effects. Herein, we designed, synthesized, and characterized six novel coumarin-triazole hybrids, and evaluated for anticancer activity of the one with the highest potential against the breast cancer cell line, MCF-7 and human cervical cancer cell line, human cervical adenocarcinoma (HeLa). Compound21which was the coumarin derivative including phenyl substituent with the lowest IC50 value displayed the highest cytotoxicity against the studied cancer cell line. Furthermore, the potential use of poly (lactic-co-glycolic acid) nanoparticles (PLGA NPs) prepared by the emulsifying solvent evaporation method as a platform for a drug delivery system was studied on a selected coumarin derivative21. This coumarin derivative-loaded PLGA NPs were produced with an average size of 225.90 ± 2.96 nm, -16.90 ± 0.85 mV zeta potential, and 4.12 ± 0.90% drug loading capacity. The obtained21-loaded PLGA nanoparticles were analyzed spectroscopically and microscopically with FT-IR, UV-vis, and scanning electron microscopy as well as thermogravimetric analysis, Raman, and x-ray diffraction. Thein vitrorelease of21from the nanoparticles exhibited a controlled release profile just over one month following a burst release in the initial six hours and in addition to this a total release ratio of %50 and %85 were obtained at pH 7.4 and 5.5, respectively.21-loaded PLGA nanoparticles displayed remarkably effective anticancer activity than21. The IC50 values were determined as IC50(21-loaded PLGA nanoparticles): 0.42 ± 0.01 mg ml-1and IC50(free21molecule): 5.74 ± 3.82 mg ml-1against MCF-7 cells, and as IC50(21-loaded PLGA nanoparticles): 0.77 ± 0.12 mg ml-1and IC50(free21molecule): 1.32 ± 0.31 mg ml-1against HeLa cells after the incubation period of 24 h. Our findings indicated that triazole-substituted coumarins may be used as an anticancer agent by integrating them into a polymeric drug delivery system providing improved drug loading and effective controlled drug release.

Multitargeting HDAC Inhibitors Containing a RAS/RAF Protein Interfering Unit

In this work, a series of multitargeting histone deacetylase (HDAC) inhibitors capable of regulating the signal transduction between RAS protein and downstream effectors were obtained by introducing a zinc-ion-binding group into the framework of rigosertib via different linkers. Among them, two representative compounds, XSJ-7 and XSJ-10, not only showed stronger antiproliferative activity against many types of cancer cells including solid tumor cells but also presented more potent inhibition on different subtypes of HDAC than suberoylanilide hydroxamic acid (SAHA). Significantly, XSJ-10 presented moderate pharmacokinetic behaviors and showed stronger antitumor activity than oxaliplatin, SAHA, and rigosertib in the HT-29 xenograft mouse models without significant systemic toxicity. Research on the anticancer mechanism of XSJ-10 revealed that it can effectively induce the apoptosis of cancer cells and suppress the tumor by strongly inhibiting the RAS-RAF-MEK-ERK signaling pathway and the acetylation level of HDAC3.

Discovery of triazole tethered thymol/carvacrol-coumarin hybrids as new class of α-glucosidase inhibitors with potent in vivo antihyperglycemic activities

Keeping in view the inhibitory potential of monoterpenes thymol and carvacrol as well as coumarin nucleus against α-glucosidase, novel series of thymol/carvacrol-coumarin hybrids was designed, synthesized and evaluated for α-glucosidase inhibitory potential. Among the series of hybrid molecules, AS14 with IC50 value of 4.32 ± 0.11 μM was selective α-glucosidase inhibitor over α-amylase (IC50 = 37.36 ± 0.84 μM). AS14 was non-toxic toward mouse normal fibroblast cells (L929: IC50 > 100 μM). Molecular docking and dynamic simulation studies confirmed desired interactions of AS14 with α-glucosidase responsible for the inhibition of its catalysis capabilities. Acute oral toxicity study confirmed AS14 as safer molecule for in vivo pharmacological investigations with LD50 value of 300 mg/kg. AS14 also showed acute hypoglycaemic effects [reduction in blood glucose levels at 1 h of administration in maltose loading test (at 10 and 20 mg/kg by 62.65 % and 70.12 %) and sucrose loading test (at 10 and 20 mg/kg by 59.65 % and 60.23 %), respectively] as well as long term (28 days) fasting blood glucose reduction (At day 28: 10 mg/kg = 54.69 % and 20 mg/kg = 62.23 % reduction in fasting blood glucose levels) capabilities in streptozotocin induced diabetic rats. Overall study represents, AS14 as potential α-glucosidase inhibitor with adequate efficacy and safety profile and act as an effective hit lead for the further development of potent and safer α-glucosidase inhibitors for the management of postprandial hyperglycemia in diabetic patients.

Progress in the development of TRPV1 small-molecule antagonists: Novel Strategies for pain management

Transient receptor potential vanilloid 1 (TRPV1) channels are widely distributed in sensory nerve endings, the central nervous system, and other tissues, functioning as ion channel proteins responsive to thermal pain and chemical stimuli. In recent years, the TRPV1 receptor has garnered significant interest as a potential therapeutic approach for various pain-related disorders, particularly TRPV1 antagonists. The present review offers a comprehensive, systematic exploration of both first- and second-generation TRPV1 antagonists in the context of pain management. Antagonists are categorized and explicated according to their structural characteristics. Detailed examination of binding modes, structural features, and pharmacological activities, alongside a critical appraisal of the advantages and limitations inherent to typical compounds within each structural category, are undertaken. Detailed discussions of the binding modes, structural features, pharmacological activities, advantages, and limitations of typical compounds within each structural category offer valuable insights and guidance for the future research and development of safer, more effective, and more targeted TRPV1 antagonists.

Arylidene and amino spacer-linked rhodanine-quinoline hybrids as upgraded antimicrobial agents

Antibiotic resistance associated with various microorganisms such as Gram-positive, Gram-negative, fungal strains, and multidrug-resistant tuberculosis increases the risk of healthcare survival. Preliminary therapeutics becoming ineffective that might lead to noteworthy mortality presents a crucial challenge for the scientific community. Hence, there is an urgent need to develop hybrid compounds as antimicrobial agents by combining two or more bioactive heterocyclic moieties into a single molecular framework with fewer side effects and a unique mode of action. This review highlights the recent advances (2013-2023) in the pharmacology of rhodanine-linked quinoline hybrids as more effective antimicrobial agents. In the drug development process, linker hybrids acquire the top position due to their excellent π-stacking and Van der Waals interaction with the DNA active sites of pathogens. A molecular hybridization strategy has been optimized, indicating that combining these two bioactive moieties with an arylidene and an amino spacer linker increases the antimicrobial potential and reduces drug resistance. Moreover, the structure-activity relationship study is discussed to express the role of various functional groups in improving and decrementing antimicrobial activities for rational drug design. Also, a linker approach may accelerate the development of dynamic antimicrobial agents through molecular hybridization.

Synthesis of novel coumarin-based thiosemicarbazones and their implications in diabetic management via in-vitro and in-silico approaches

Diabetes mellitus has a high prevalence rate and it has been deemed a severe chronic metabolic disorder with long-term complications. This research aimed to identify compounds that could potentially inhibit the vital metabolic enzyme α-glucosidase and thereby exert an anti-hyperglycemic effect. The main goal was to establish an effective approach to control diabetes. To proceed with this study, a series of novel coumarin-derived thiosemicarbazones 3a-3m was synthesized and examined using a variety of spectroscopic methods. Moreover, all the compounds were subjected to α-glucosidase inhibition bioassay to evaluate their antidiabetic potential. Fortunately, all the compounds exhibited several folds potent α-glucosidase inhibitory activities with IC50 values ranging from 2.33 to 22.11 µM, in comparison to the standard drug acarbose (IC50 = 873.34 ± 1.67 µM). The kinetic studies of compound 3c displayed concentration-dependent inhibition. Furthermore, the binding modes of these molecules were elucidated through a molecular docking strategy which depicted that the thiosemicarbazide moiety of these molecules plays a significant role in the interaction with different residues of the α-glucosidase enzyme. However, their conformational difference is responsible for their varied inhibitory potential. The molecular dynamics simulations suggested that the top-ranked compounds (3c, 3g and 3i) have a substantial effect on the protein dynamics which alter the protein function and have stable attachment in the protein active pocket. The findings suggest that these molecules have the potential to be investigated further as novel antidiabetic medications.

Recent research of BTK inhibitors: Methods of structural design, pharmacological activities, manmade derivatives and structure-activity relationship

Protein kinases constitute the largest group within the kinase family, and mutations and translocations of protein kinases due to genetic alterations are intimately linked to the pathogenesis of numerous diseases. Bruton's tyrosine kinase (BTK) is a member of the protein kinases and plays a pivotal role in the development and function of B cells. BTK belongs to the tyrosine TEC family. The aberrant activation of BTK is closely associated with the pathogenesis of B-cell lymphoma. Consequently, BTK has always been a critical target for treating hematological malignancies. To date, two generations of small-molecule covalent irreversible BTK inhibitors have been employed to treat malignant B-cell tumors, and have exhibited clinical efficacy in hitherto refractory diseases. However, these drugs are covalent BTK inhibitors, which inevitably lead to drug resistance after prolonged use, resulting in poor tolerance in patients. The third-generation non-covalent BTK inhibitor Pirtobrutinib has obtained approval for marketing in the United States, thereby circumventing drug resistance caused by C481 mutation. Currently, enhancing safety and tolerance constitutes the primary issue in developing novel BTK inhibitors. This article systematically summarizes recently discovered covalent and non-covalent BTK inhibitors and classifies them according to their structures. This article also provides a detailed discussion of binding modes, structural features, pharmacological activities, advantages and limitations of typical compounds within each structure type, providing valuable references and insights for developing safer, more effective and more targeted BTK inhibitors in future studies.

Designing Potent α-Glucosidase Inhibitors: A Synthesis and QSAR Modeling Approach for Biscoumarin Derivatives

Nineteen biscoumarins were synthesized, well-characterized, and evaluated against α-glucosidases in vitro. Of these, six compounds (10, 12, 16, and 17-19) were newly synthesized and not previously reported in the chemical literature. The majority of the synthesized derivatives demonstrated significant inhibitory activity. A quantitative structure-activity relationship (QSAR) model was developed, revealing a strong correlation between the anti-α-glucosidase activity and selected molecular descriptors. Based on this model, two new compounds (18 and 19) were designed, which exhibited the strongest inhibition with IC₅₀ values of 0.62 and 1.21 μM, respectively, when compared to the positive control (acarbose) with an IC₅₀ value of 93.63 μM. Enzyme kinetic studies of compounds 18 and 19 revealed their competitive inhibition with K_i values of 3.93 and 1.80 μM, respectively. Computational studies demonstrated that compound 18 could be inserted into the original binding site (OBS) of α-glucosidase MAL12 and form multiple hydrophobic interactions with nearby amino acids, with the bromo group playing an essential role in enhancing the binding strength and stability at the OBS of the enzyme based on the quantum mechanical calculations using the fragment molecular orbital method. These findings provide valuable insights into the design of potent α-glucosidase inhibitors, which may have potential therapeutic applications in the treatment of diabetes and related diseases.

Progress and Development of Carbazole Scaffold Based as Potential Anti- Alzheimer Agents Using MTDL Approach

Abstract:

Alzheimer’s is a neurodegenerative disease (NDs) found in old age people with associated most common symptom dementia. MTDLs (Multi-Target Direct Ligand strategy) is based on a combination of two or more bioactive pharmacophores into a single molecule and this phenomenon has received a great attention in the new era of modern drug discovery and emerging as a choice to treat this complex Alzheimer’s disease (AD). In last fifteen years, many research groups designed, and synthesized new carbazole integrated molecules linked with other bioactive pharmacophores like thiazoles, carvedilol, α- naphthylaminopropan-2-ol, tacrine, ferulic acid, piperazine, coumarin, chalcones, stilbene, benzyl piperidine, adamantane, quinoline, phthalocyanines, α-amino phosphonate, thiosemicarbazones, hydrazones, etc. derivatives using MTDLs approach to confront AD. The present review entails the scientific data on carbazole hybrids as potential Anti-Alzheimer activities from 2007 to 2021 that have shown potential anti-Alzheimer activities through multiple target pathways thereby promising hope for new drug development to confront AD.

Application of COSMO-RS-DARE as a Tool for Testing Consistency of Solubility Data: Case of Coumarin in Neat Alcohols

Coumarin is a naturally occurring lactone-type benzopyrone with various applications in the pharmaceutical, food, perfume, and cosmetics industries. This hydrophobic compound is poorly soluble in water but dissolves well in protic organic solvents such as alcohols. Despite the extensive use of coumarin, there are only a few reports documenting its solubility in organic solvents, and some reported data are incongruent, which was the direct impulse for this study. To resolve this problem, a theoretical congruency test was formulated using COSMO-RS-DARE for the determination of intermolecular interaction parameters, which allowed for the identification of outliers as suspicious datasets. The perfect match between back-computed values of coumarin solubility and the experimental ones confirms the reliability of the formulated theoretical approach and its adequacy for testing solubility data consistency. As the final approval, the temperature-related coumarin solubility in seven neat alcohols was determined experimentally. Four solvents (methanol, ethanol, 1-propanol, and 2-propanol) were used for reproducibility purposes, and an additional three (1-butanol, 1-pentanol, and 1-octanol) were used to extend the information on the homologous series. The consistency of this extended solubility dataset is discussed in terms of the comparison of remeasured solubility values with the ones already published and within the series of structurally similar solvents. The proposed procedure extends the range of applicability of COSMO-RS-DARE and provides a real and useful tool for consistency tests of already published solubility data, allowing for the approval/disapproval of existing data and filling gaps in datasets. Linear regressions utilizing a 2D molecular descriptor, SpMin2_Bhm, or the distance between solute and solvent in the Hansen solubility space, Ra, were formulated for the estimation of COMSO-RS-DARE integration parameters.

Aminoalkoxy-substituted coumarins: Synthesis and evaluation for reactivation of inhibited human acetylcholinesterase

Reactivation of inhibited acetylcholinesterase remains an important therapeutic strategy for the treatment of poisoning by organophosphorus compounds, such as nerve agents or pesticides. Although drugs like obidoxime or pralidoxime have been used with considerable success, there is a need for new substances capable of reactivating acetylcholinesterase with a broader scope and increased efficacy. Possible screening candidates must fulfill two fundamental requirements: They must (i) show an affinity to acetylcholinesterase well balanced between sufficient binding and competitive inhibition and (ii) facilitate the nucleophilic cleavage of the phosphorylated catalytic serine residue. We attached a variety of nonaromatic primary and secondary amines to a coumarin core through selected alkoxy side linkers attached at coumarin positions 6 or 7 to obtain a small set of possible reactivators. Evaluation of their inhibition and reactivation potential in vitro showed some activity with respect to acetylcholinesterase inhibited by cyclosarin.

Phytochemical profile and biological activities of Bromelia antiacantha extracts

Reports from popular medicine usually act as a basis for the development of new drugs from natural compounds with therapeutic actions for serious diseases and prevalence such as cancer. Bromelia antiacantha Bertol. is a species of the Bromeliaceae family, considered an unconventional food plant, found in the south and midwest regions of Brazil. Despite the high nutritional content and pharmacological potential of its fruits, few scientific studies report its biological actions. Thus, this study evaluates the phytochemical profile of aqueous and ethanol extracts obtained from B. antiacantha fruits, as well as their possible antioxidant, antitumor, and cytotoxic activities. The aqueous extract exhibited phenolic compounds and flavonoids, while ethanol extracts indicated the presence of flavonoids and coumarin in their composition, regardless of the region of collection. The ethanolic extract demonstrated a more promising antioxidant effect than the aqueous extract and also induced a significant inhibition in the viability of human cervical cancer cells of the SiHa strain. In addition, treatment with both extracts did not alter the viability of non-tumor cells of the immortalized human keratinocyte lineage (HaCaT). These results bring new data about extracts obtained from a native plant, edible and traditionally used in popular medicine, opening new perspectives for its possible therapeutic application.

Interactions of coumarin derivatives with monoamine oxidase biomarkers: In silico approach

A list of coumarin derivatives (A-P) were investigated in this work for recognizing their reactivity features and their functions towards the monoamine oxidase (MAO) enzyme biomarkers. In this regard, the models showed that he additional of molecular groups to the original scaffold of coumarin could significantly change the reactivity features leading to various tendency for contributing to reactions with other substances. In this case, were varied based on the obtained values of chemical hardness and softness parameters. Subsequently, formations of interacting ligand-target complexes indicated the coumarin derivatives could work as selective substances for interacting with each of MAOA (D) and MAOB (L) enzyme biomarkers, in which a common substance (E) was also observed for formation of interacting complexes with both of MAOA and MAOB targets. As a consequence, the models of coumarin were seen suitable for interacting with the MAO enzyme biomarkers with the purposes of detection and medication. All required information of this work were obtained in the in silico medium.

The hybrid compounds as multi-target ligands for the treatment of Alzheimer's Disease: Considerations on Donepezil

The strategies to combat Alzheimer's Disease (AD) have been changing with respect to the failures of many drug candidates assessed in clinical studies, the complex pathophysiology of AD, and the limitations of the current drugs employed. So far, none of the targets, either validated or nonvalidated, have been shown to be purely causative in the generation and development of AD. Considering the progressive and the neurodegenerative characteristics of the disease, the main strategy has been based on the design of molecules capable of showing activity on more than one receptor, and it is defined as multi-target ligand design strategy. The hybrid molecule concept is an outcome of this approach. Donepezil, as one of the currently employed drugs for AD therapy, has also been utilized in hybrid drug design studies. This review has aimed to present the promising donepezil-like hybrid molecules introduced in the recent period. Particularly, multi-target ligands with additional activities concomitant to cholinesterase inhibition are preferred.

Advances in the application of 1,2,4-triazole-containing hybrids as anti-tuberculosis agents

Tuberculosis is a deadly communicable disease caused by the bacillus Mycobacterium tuberculosis (MTB), and pulmonary tuberculosis accounts for over 80% of the total cases. The 1,2,4-triazole is a privileged structure in the discovery of new drugs, and its derivatives act on various targets in MTB. In particular, 1,2,4-triazole hybrids can not only exert dual or multiple antitubercular mechanisms of action but also have the potential to enhance efficacy and reduce side effects. The present work aims to summarize the current status of 1,2,4-triazole hybrids as potential antitubercular agents, covering articles published between 2010 and 2020, to aid the further rational design of novel potential drug candidates endowed with higher efficacy, better compliance and fewer side effects.

human monoamine oxidase (hMAO) A and hMAO B inhibitors from Artemisia dracunculus L. herniarin and skimmin: human mononamine oxidase A and B inhibitors from A. dracunculus L

The aim of this study was to investigate the effects of extracts and pure Artemisia dracunculus L. (tarragon) metabolites on the antimonoamine oxidase and anticholinesterase activities. The compounds were characterized as stigmasterol (1), herniarin (2), (2E,4E)-1-(piperidin-1-yl)undeca-2,4-diene-8,10-diyn-1-one (3), (2E,4E)-N-isobutylundeca-2,4-dien-8,10-diynamide (4), 3,4-dehydroherniarin (5) and skimmin (6) by 1H-NMR, 13C-NMR, 1D and 2D NMR methods. The compounds 5 and 6 were isolated from tarragon for the first time. The extracts and pure compounds have inhibitory effects on the human monoamine oxidase (hMAO) A and B enzymes, whereas they did not exhibit any anticholinesterase activities. Among the tarragon compounds, only 2 and 6 compounds showed the inhibitory effects against hMAO A (IC50 = 51.76 and 73.47 μM, respectively) and hMAO B (IC50 = 0.84 and 1.63 mM, respectively). In the study, herniarin content in the extracts was also analysed by high-performance liquid chromatography and it was found that there was a relationship between the inhibition effects of the extracts and their herniarin content.

Quinoline-based Compounds with Potential Activity against Drugresistant Cancers

Drug resistance is the major cause of the failure of cancer chemotherapy, so one of the most important features in developing effective cancer therapeutic strategies is to overcome drug resistance. Quinoline moiety has become one of the most privileged structural motifs in anticancer agent discovery since its derivatives possess potent activity against various cancers including drug-resistant cancers. Several quinoline-based compounds which are represented by Anlotinib, Bosutinib, Lenvatinib, and Neratinib have already been applied in clinical practice to fight against cancers, so quinoline-based compounds are potential anticancer agents. The present short review article provides an overview of the recent advances of quinoline-based compounds with potential activity against drug-resistant cancers. The structure-activity relationship and mechanisms of action are also discussed.

A Comprehensive Review of Monoamine Oxidase-A Inhibitors in their Syntheses and Potencies

BACKGROUND

Monoamine oxidases (MAOs) play a crucial role during the development of various neurodegenerative disorders. There are two MAO isozymes, MAO-A and MAO-B. MAO-A is a flavoenzyme, which binds to the outer mitochondrial membrane and catalyzes the oxidative transformations of neurotransmitters like serotonin, norepinephrine, and dopamine.

MATERIALS AND METHODS

Focus on synthetic studies has culminated in the preparation of many MAOA inhibitors, and advancements in combinatorial and parallel synthesis have accelerated the developments of synthetic schemes. Here, we provided an overview of the synthetic protocols employed to prepare different classes of MAO-A inhibitors. We classified these inhibitors according to their molecular scaffolds and the synthetic methods used.

RESULTS

Various synthetic and natural derivatives from a different class of MAO-A inhibitors were reported.

CONCLUSION

The review provides a valuable tool for the development of a new class of various selective MAO-A inhibitors for the treatment of depression and other anxiety disorders.

Synthesis and potent antimicrobial activity of novel coumarylthiazole α-aminophosphonates derivatives

Herein, we reported a novel series of α-aminophosphonates derivatives (IV)a-m bearing an important pharmacophore coumarylthiazole moiety. All the new compounds have been synthesized via Kabachnik-Fields reaction under ultrasonic irradiation. The products were obtained in good yield with a simple workup and were confirmed using various spectroscopic methods. All these compounds (IV)a-m were screened for their in vitro for antimicrobial activity against thirteen Gram-negative bacteria and five Gram-positive bacteria and Candida albicans strains. The results showed that all the synthesized compounds exhibited moderate antibacterial activities against both references and multidrug-resistant and antifungal strains. The compound (IV)e showed the highest activities against all pathogens of the tested microbial strains with MIC of 0.125 μg/mL. The compounds (IV)h, (IV)f, (IV)b, and (IV)d exhibited moderate and promising activities with MIC of 0.125 μg/mL. Structure-activity relationship revealed that inhibitory activity of the synthesized compounds is related to the type of the substituted group on phenyl rings, and these results showed that the electron-donating groups at ortho and para positions have a high relationship increasing antimicrobial activities than the electron-withdrawing groups. These results confirm that coumarylthiazole α-aminophosphonates compounds can be potential antimicrobial drugs candidate.

Structural exploration of multifunctional monoamine oxidase B inhibitors as potential drug candidates against Alzheimer's disease

AD is one of the most typical neurodegenerative disorders that suffer many seniors worldwide. Recently, MAO inhibitors have received increasing attention not only for their roles involved in monoamine neurotransmitters metabolism and oxidative stress but also for their additional neuroprotective and neurorescue effects against AD. The curiosity in MAO inhibitors is reviving, and novel MAO-B inhibitors recently developed with ancillary activities (e.g., Aβ aggregation and AChE inhibition, anti-ROS and chelating activities) have been proposed as multitarget drugs foreshadowing a positive outlook for the treatment of AD. The current review describes the recent development of the design, synthesis, and screening of multifunctional ligands based on MAO-B inhibition for AD therapy. Structure-activity relationships and rational design strategies of the synthetic or natural product derivatives (chalcones, coumarins, chromones, and homoisoflavonoids) are discussed.

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.

Coumarin-based Scaffold as α-glucosidase Inhibitory Activity: Implication for the Development of Potent Antidiabetic Agents

BACKGROUND

Delaying the absorption of glucose through α-glucosidase enzyme inhibition is one of the therapeutic approaches in the management of Type 2 diabetes, which can reduce the incidence of postprandial hyperglycemia. The existence of chronic postprandial hyperglycemia impaired the endogenous antioxidant defense by inducing oxidative stress-induced pancreatic β-cell destruction through uncontrolled generation of free radicals such as ROS, which in turn, leads to various macrovascular and microvascular complications. The currently available α -glucosidase inhibitors, for instance, acarbose, have some side effects such as hypoglycemia at higher doses, liver problems, meteorism, diarrhea, and lactic acidosis. Therefore, there is an urgent need to discover and develop potential α-glucosidase inhibitors.

OBJECTIVE

Based on suchmotifs, researchers are intrigued to search for the best scaffold that displays various biological activities. Among them, coumarin scaffold has attracted great attention. The compound and its derivatives can be isolated from various natural products and/or synthesized for the development of novel α-glucosidase inhibitors.

RESULTS

This study focused on coumarin and its derivatives as well as on their application as potent antidiabetic agents and has also concentrated on the structure-activity relationship.

CONCLUSION

This review describes the applications of coumarin-containing derivatives as α - glucosidase inhibitors based on published reports which will be useful for innovative approaches in the search for novel coumarin-based antidiabetic drugs with less toxicity and more potency.

Access to 4-Alkenylated Coumarins via Ruthenium-Catalyzed Olefinic C-H Alkenylation of Coumarins with Modifiable and Removable Directing Groups

The ruthenium-catalyzed activation of the C4 position of coumarins for coupling with acrylates was described using modifiable ketone as a directing group. The alkenylation reaction provided a direct approach to prepare previously inaccessible 4-alkenylated coumarins with operational simplicity and high atom-economy. This protocol also worked well with coumarin-3-carboxylic acids to unveil a rare instance of a tandem alkenylation/decarboxylation reaction. The potential value of this approach was further highlighted by the efficient synthesis of several heterocyclic fused coumarin derivatives.

Water Soluble Coumarin Quaternary Ammonium Chlorides: Synthesis and Biological Evaluation

In the present study, coumarin-bearing three pyridinium and three tetra-alkyl ammonium salts were synthesized. The compounds were fully characterized by ¹ H- and ¹³ C-NMR, LC/MS and IR spectroscopic methods and elemental analyses. The cytotoxic properties of all compounds were tested against human liver cancer (HepG2), human colorectal cancer (Caco-2) and non-cancer mouse fibroblast (L-929) cell lines. Some compounds performed comparable cytotoxicity with standard drug cisplatin. Antibacterial properties of the compounds were tested against Gram-negative Escherichia coli and Gram-positive Bacillus subtilis bacteria, but the compounds did not have any antibacterial effect against both bacteria. Enzyme inhibitory properties of all compounds were tested on the activities of human carbonic anhydrase I and II, and xanthine oxidase. All compounds inhibited both enzymes more effectively than standard drugs, acetazolamide and allopurinol, respectively. The biological evaluation results showed that ionic and water soluble coumarin derivatives are promising structures for further investigations especially on enzyme inhibition field.

Synthesis of furocoumarin-stilbene hybrids as potential multifunctional drugs against multiple biochemical targets associated with Alzheimer's disease

A series of furocoumarin-stilbene hybrids has been synthesized and evaluated in vitro for inhibitory effect against acetylcholinesterase (AChE), butyrylcholinestarase (BChE), β-secretase, cyclooxygenase-2 (COX-2), and lipoxygenase-5 (LOX-5) activities including free radical-scavenging properties. Among these hybrids, 8-(3,5-dimethoxyphenyl)-4-(3,5-dimethoxystyryl)furochromen-2-one 4h exhibited significant anticholinesterase activity and inhibitory effect against β-secretase, COX-2 and LOX-5 activities. 2,2-Diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity and an in vitro cell-based antioxidant activity assay involving lipopolysaccharide induced reactive oxygen species production revealed that 4h has capability of scavenging free radicals. Molecular docking into AChE, BChE, β-secretase, COX-2 and LOX-5 active sites has also been performed.

To be ionized or not to be ionized: the vital role of physicochemical properties of galbanic acid derivatives in AChE assay

Alzheimer's disease is a progressive neurodegenerative disorder and patients suffer from memory loss, a decline in language skill and impairment in other cognitive functions. In the cholinergic hypothesis, dysfunction of cholinergic neurons especially in the hippocampus and cerebral cortex contributes to cognitive decline in patients. So agents that enhance acetylcholine concentration could improve cognitive function. AChEIs are among the most studied anti-Alzheimer agents. Galbanic acid as a natural compound with a sesquiterpene coumarin scaffold is a weak inhibitor of AChE. In the present contribution, we discussed the impact of carboxylic group ionization on inhibitory effects. We performed in vitro and in silico studies on galbanic acid, methyl and ethyl galbanates as AChE inhibitors. The order of inhibitory effect on AChE was obtained as ethyl galbanate ∼ methyl galbanate > galbanic acid. Our study highlights the important role of the physicochemical properties of natural lead compounds in each specific assay.Communicated by Ramaswamy H. Sarma.

Current scenario of indole derivatives with potential anti-drug-resistant cancer activity

Cancer chemotherapy is frequently hampered by drug resistance, so the resistance to anticancer agents represents one of the major obstacles for the effective cancer treatment. Indole derivatives have the potential to act on diverse targets in cancer cells and exhibit promising activity against drug-resistant cancers. Moreover, some indole-containing compounds such as Semaxanib, Sunitinib, Vinorelbine, and Vinblastine have already been applied in clinics for various kinds of cancer even drug-resistant cancer therapy. Thus, indole derivatives are one of significant resources for the development of novel anti-drug-resistant cancer agents. This review focuses on the recent development of indole derivatives with potential therapeutic application for drug-resistant cancers, and the mechanisms of action, the critical aspects of design as well as structure-activity relationships, covering articles published from 2010 to 2020.

Coumarin-containing hybrids and their antibacterial activities

Infections caused by Gram-positive and -negative bacteria are one of the foremost causes of morbidity and mortality globally. Antibiotics are the mainstay of therapy for bacterial infections, but the emergence and wide spread of drug-resistant pathogens have already become a huge issue for public healthcare systems. The coumarin moiety, which is ubiquitous in nature, could bind to the B subunit of DNA gyrase in bacteria and inhibit DNA supercoiling by blocking the ATPase activity; hence, coumarin derivatives possess potential antibacterial activity. Several coumarin-containing hybrids such as coumermycin A1, clorobiocin, and novobiocin have already been used in clinical practice for the treatment of various bacterial infections; thus, it is conceivable that hybridization of the coumarin moiety with other antibacterial pharmacophores may provide opportunities for the development of novel antibiotics. This review outlines the advances in coumarin-containing hybrids with antibacterial potential in the recent 5 years and the structure-activity relationships are also discussed.

Synthesis, Biological Evaluation and Molecular Docking of Deferasirox and Substituted 1,2,4-Triazole Derivatives as Novel Potent Urease Inhibitors: Proposing Repositioning Candidate

A series of new deferasirox derivatives were synthesized through the reaction of monosubstituted hydrazides with 2-(2-hydroxyphenyl)-4H-benzo[e][1,3]oxazin-4-one. For the first time, deferasirox and some of its derivatives were evaluated for their in vitro inhibitory activity against Jack bean urease. The potencies of the members of this class of compounds are higher than that of acetohydroxamic acid. Two compounds, bearing tetrazole and hydrazine derivatives (bioisoester of carboxylate group), represented the most potent urease inhibitory activity with IC₅₀ values of 1.268 and 3.254 μm, respectively. In silico docking studies were performed to delineate possible binding modes of the compounds with the enzyme, urease. Docking analysis suggests that the synthesized compounds were anchored well in the catalytic site and extending to the entrance of binding pocket and thus restrict the mobility of the flap by interacting with its crucial amino acid residues, CME592 and His593. The overall results of urease inhibition have shown that these target compounds can be further optimized and developed as a lead skeleton for the discovery of novel urease inhibitors.

Design, synthesis and biological evaluation of coumarin linked 1,2,4-oxadiazoles as selective carbonic anhydrase IX and XII inhibitors

A series of coumarin linked 1,2,4-oxadiazoles were synthesized and the synthesized compounds were subjected for evaluation against the four physiologically and pharmacologically relevant hCA isoforms, hCA I, II, IX and XII. Upon evaluation of the results, it was inferred that the coumarin linked 1,2,4-oxadiazoles showed selective hCA IX and XII inhibition (low to medium nanomolar range) over hCA I and II (>10000 nM). The inhibition constants ranged from low nanomolar to moderately nanomolar. Compounds 6o, 6a, 6q and 6c elicited hCA XII inhibition, with K_i values lower than that of the standard, Acetazolamide (AAZ) with compound 6o exhibiting a K_i value of 1 nM., against hCA IX, the compound 6c exhibited the most potent inhibition with a K_i value of 23.6 nM. Hence, compound 6o can be taken as an effective lead compound for the development of hCA XII inhibitors and compound 6c can be taken as a lead compound for the development of dual hCA IX and XII inhibitors. To understand the molecular interactions, the two most potent compounds 6a and 6o were docked within the hCA XII catalytic cleft in order to study their binding modes with that isoform.

Novel 3-aryl-5-substituted-coumarin analogues: Synthesis and bioactivity profile

Eighteen 3-aryl-5-substituted-coumarins-six 5-acetyloxy-derivatives, six 5-hydroxy-derivatives, and six 5-geranyloxy-derivatives-were synthesized, structurally characterized and their antioxidant activity, lipoxygenase inhibitory ability, as well as their cytotoxic activity against human neuroblastoma SK-N-SH and HeLa adenocarcinoma cell lines were evaluated. The 5-acetyloxy-compounds 3a-3f were found to be the best cytotoxic agents among all the compounds studied. The bromo-substituted coumarins 3a and 3b were remarkably active against HeLa cell line showing IC₅₀ 1.8 and 6.1 μM, respectively. Coumarin 5e possessing a geranyloxy-chain on position 5 of the coumarin scaffold presented dual bioactivity, while 5-geranyloxy-coumarin 5f was the most competent soybean lipoxygenase inhibitor of this series (IC₅₀ 10 μM). As shown by in silico docking studies, the studied molecules present allosteric interactions with soybean lipoxygenases.

Synthesis of 1-(β-coumarinyl)-1-(β-indolyl)trifluoroethanols through regioselective Friedel–Crafts alkylation of indoles with β-(trifluoroacetyl)coumarins catalyzed by Sc(OTf)3

A highly efficient Friedel–Crafts alkylation of indole derivatives with β-(trifluoroacetyl)coumarins using Sc(OTf)₃ as a catalyst has been developed, which gives regioselective 1,2-adducts to afford 1-(β-coumarinyl)-1-(β-indolyl)trifluoroethanols. A series of tertiary trifluoroethanols containing different indole and coumarin groups were synthesized in moderate to excellent yields (up to 95%) in the presence of 5 mol% catalyst in a short time (only 2 minutes at least). A mechanism of the reaction, in which the trace amount of water plays the role of proton transfer in catalyzing circulation was proposed and confirmed.

A Friedel–Crafts alkylation of indoles with β-(trifluoroacetyl)coumarins catalyzed by Sc(OTf)₃ to afford 1-(β-coumarinyl)-1-(β-indolyl)trifluoroethanols in a short time and high yield was developed.

Promising New Inhibitors of Tyrosyl-DNA Phosphodiesterase I (Tdp 1) Combining 4-Arylcoumarin and Monoterpenoid Moieties as Components of Complex Antitumor Therapy

Tyrosyl-DNA phosphodiesterase 1 (Tdp1) is an important DNA repair enzyme in humans, and a current and promising inhibition target for the development of new chemosensitizing agents due to its ability to remove DNA damage caused by topoisomerase 1 (Top1) poisons such as topotecan and irinotecan. Herein, we report our work on the synthesis and characterization of new Tdp1 inhibitors that combine the arylcoumarin (neoflavonoid) and monoterpenoid moieties. Our results showed that they are potent Tdp1 inhibitors with IC₅₀ values in the submicromolar range. In vivo experiments with mice revealed that compound 3ba (IC₅₀ 0.62 µM) induced a significant increase in the antitumor effect of topotecan on the Krebs-2 ascites tumor model. Our results further strengthen the argument that Tdp1 is a druggable target with the potential to be developed into a clinically-potent adjunct therapy in conjunction with Top1 poisons.