Remarkable antioxidant properties of a series of hydroxy-3-arylcoumarins

Facile One-Pot Conversion of (poly)phenols to Diverse (hetero)aryl Compounds by Suzuki Coupling Reaction: A Modified Approach for the Synthesis of Coumarin- and Equol-Based Compounds as Potential Antioxidants

A series of 16 (hetero)aryl compounds based on coumarin and equol has been efficiently synthesized by exploring the palladium-catalyzed Suzuki cross-coupling reactions. Polyphenol based on coumarin (4-methyl-7-hydroxy coumarin) was initially converted to corresponding coumarin imidazylate and then subjected to Suzuki coupling reaction with 4-methoxyphenylboronic acid to obtain the coupled product. This modified approach was later developed into a one-pot methodology by directly reacting the polyphenol with 1,1-sulfonyldiimidazole (SDI) and boronic acid in situ to obtain the Suzuki coupled product in one step. Moreover, an array of (poly)phenols based on coumarin and equol were later converted to diverse (hetero)aryl compounds by this optimized step-economic protocol. The synthesized compounds were then subjected to the screening of their potential antioxidant activities by 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay. In our investigation, the compounds 4ah, 4eh, 4gh and 4hh exhibited promising antioxidant potential when compared to the reference standard, butylated hydroxytoluene (BHT). Structure activity relationship (SAR) studies revealed the importance of the presence of electron-donating substituents in enhancing the antioxidant activity of the synthesized compounds.

Chromenone: An emerging scaffold in anti-Alzheimer drug discovery

Alzheimer's disease (AD) presents a growing global health concern. In recent decades, natural and synthetic chromenone have emerged as promising drug candidates due to their multi-target potential. Natural chromenone, quercetin, scopoletin, esculetin, coumestrol, umbelliferone, bergapten, and methoxsalen (xanthotoxin), and synthetic chromenone hybrids comprising structures like acridine, 4-aminophenyl, 3-arylcoumarins, quinoline, 1,3,4-oxadiazole, 1,2,3-triazole, and tacrine, have been explored for their potential to combat AD. Key reactions used for synthesis of chromenone hybrids include Perkin and Pechmann condensation. The activity of chromenone hybrids has been reported against several drug targets, including AChE, BuChE, BACE-1, and MAO-A/B. This review comprehensively explores natural, semisynthetic, and synthetic chromenone, elucidating their synthetic routes, possible mode of action/drug targets and structure-activity relationships (SAR). The acquired knowledge provides valuable insights for the development of new chromenone hybrids against AD.

Discovery of Benzopyrone-Based Candidates as Potential Antimicrobial and Photochemotherapeutic Agents through Inhibition of DNA Gyrase Enzyme B: Design, Synthesis, In Vitro and In Silico Evaluation

Bacterial DNA gyrase is considered one of the validated targets for antibacterial drug discovery. Benzopyrones have been reported as promising derivatives that inhibit bacterial DNA gyrase B through competitive binding into the ATP binding site of the B subunit. In this study, we designed and synthesized twenty-two benzopyrone-based derivatives with different chemical features to assess their antimicrobial and photosensitizing activities. The antimicrobial activity was evaluated against B. subtilis, S. aureus, E. coli, and C. albicans. Compounds 6a and 6b (rigid tetracyclic-based derivatives), 7a-7f (flexible-linker containing benzopyrones), and 8a-8f (rigid tricyclic-based compounds) exhibited promising results against B. subtilis, S. aureus, and E. coli strains. Additionally, these compounds demonstrated photosensitizing activities against the B. subtilis strain. Both in silico molecular docking and in vitro DNA gyrase supercoiling inhibitory assays were performed to study their potential mechanisms of action. Compounds 8a-8f exhibited the most favorable binding interactions, engaging with key regions within the ATP binding site of the DNA gyrase B domain. Moreover, compound 8d displayed the most potent IC50 value (0.76 μM) compared to reference compounds (novobiocin = 0.41 μM and ciprofloxacin = 2.72 μM). These results establish a foundation for structure-based optimization targeting DNA gyrase inhibition with antibacterial activity.

Chemical composition and bioactivity variability of two-step extracts derived from traditional and "QiNan" agarwood (Aquilaria spp.)

One of the primary applications for agarwood lies in the extracts, instead, there are obvious differences in the demands for agarwood components with different application fields. To obtain the rough separation and clarify each part's activity, four extracts of essential oil, hydrolat, extractum, and ethanol precipitation from traditional agarwood (TraA) and "Qinan" agarwood (QinA) were obtained by steam-solvent multistage extraction and ethanol precipitation. We investigated the chemistry and biological activity of multistage extracts using gas chromatography-mass spectrometry (GC-MS), high-performance liquid chromatography (HPLC), and in vitro activity testing. The results demonstrated that two kinds of agarwood essential oils contained mainly sesquiterpenoids, yet the sesquiterpene species were remarkably diverse in two kinds of agarwood essential oils. Then, the TraA and QinA hydrolat, all predominantly aromatic and sesquiterpene, but with differences from the essential oil ingredients. Additionally, the extractum chiefly contained chromones and the ethanol precipitation method worked well to separate the impurities in the TraA extract, however, it was ineffective for the QinA extract. Ultimately, essential oils and extractums all have antioxidant properties, with extractums outperforming essential oils. Moreover, both extractums and essential oils exhibited excellent broad-spectrum antimicrobial activity and anti-inflammatory activity. The findings pointed to the feasibility of separating the primary components from TraA and QinA using a multi-stage extraction technique, providing a scientific basis for the efficient utilization of all components of agarwood, as well as the functional product development and differentiated utilization of extract products in incense, fragrance, perfume, and daily chemicals.

Study of the DNA damage and cell death in human peripheral blood mononuclear and HepG2/C3A cells exposed to the synthetic 3-(3-hydroxyphenyl)-7-hydroxycoumarin

Hydroxycoumarins are an important source of biologically active compounds. Previous studies have shown that the number and position of the hydroxyl substituents in the scaffold play an important role for the observed biological activity. In the present study, 3-(3-hydroxyphenyl)-7-hydroxycoumarin was synthesized, and potential cytogenotoxic effects determined in human HepG2/C3A cells displaying phase 1 and phase 2 enzymes (metabolizing cell ability) and compared to human peripheral blood mononuclear cells (PBMC) without xenobiotics metabolizing capacity. Cell viability was determined with concentrations between 0.01 and 10 µg/ml of 3-(3-hydroxyphenyl)-7-hydroxycoumarin using MTT (3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide) and trypan blue tests. Genotoxicity was determined utilizing the comet assay, and the clastogenic/aneugenic potential employing the micronucleus (MN) test. The results of the in vitro cytotoxicity assays showed a significant decrease in cell viability of PBMC following exposure to 10 µg/ml concentration of the studied compound after 48 and 72 hr. Comet assay observations noted significant DNA damage in PBMC after 4 hr treatment. No marked cytogenotoxic effects were found in HepG2/C3A cells. No chromosomal mutations were observed in both cell lines. It is important to note that 3-(3-hydroxyphenyl)-7-hydroxycoumarin may exert beneficial pharmacological actions at the low micromolar range and with half-life less than 24 hr. Therefore, the results obtained encourage the continuation of studies on this new molecule for medicinal purposes, but its potential toxicity at higher concentrations and longer exposure times needs to be investigated in further studies.

Recent Advancements and SAR Studies of Synthetic Coumarins as MAO-B Inhibitors: An Updated Review

BACKGROUND

The oxidative deamination of a wide range of endogenous and exogenous amines is catalyzed by a family of enzymes known as monoamine oxidases (MAOs), which are reliant on flavin-adenine dinucleotides. Numerous neurological conditions, such as Parkinson's disease (PD) and Alzheimer's disease (AD), are significantly correlated with changes in the amounts of biogenic amines in the brain caused by MAO. Hydrogen peroxide, reactive oxygen species, and ammonia, among other toxic consequences of this oxidative breakdown, can harm brain cells' mitochondria and cause oxidative damage.

OBJECTIVE

The prime objective of this review article was to highlight and conclude the recent advancements in structure-activity relationships of synthetic derivatives of coumarins for MAO-B inhibition, published in the last five years' research articles.

METHODS

The literature (between 2019 and 2023) was searched from platforms like Science Direct, Google Scholar, PubMed, etc. After going through the literature, we have found a number of coumarin derivatives being synthesized by researchers for the inhibition of MAO-B for the management of diseases associated with the enzyme such as Alzheimer's Disease and Parkinson's Disease. The effect of these coumarin derivatives on the enzyme depends on the substitutions associated with the structure. The structure-activity relationships of the synthetic coumarin derivatives that are popular nowadays have been described and summarized in the current study.

RESULTS

The results revealed the updated review on SAR studies of synthetic coumarins as MAO-B inhibitors, specifically for Alzheimer's Disease and Parkinson's Disease. The patents reported on coumarin derivatives as MAO-B inhibitors were also highlighted.

CONCLUSION

Recently, coumarins, a large class of chemicals with both natural and synthetic sources, have drawn a lot of attention because of the vast range of biological actions they have that are linked to neurological problems. Numerous studies have demonstrated that chemically produced and naturally occurring coumarin analogs both exhibited strong MAO-B inhibitory action. Coumarins bind to MAO-B reversibly thereby preventing the breakdown of neurotransmitters like dopamine leading to the inhibition of the enzyme A number of MAO-B blockers have been proven to be efficient therapies for treating neurological diseases like Alzheimer's Disease and Parkinson's Disease. To combat these illnesses, there is still an urgent need to find effective treatment compounds.

Monoamine oxidase B inhibitors based on natural privileged scaffolds: A review of systematically structural modification

Monoamine oxidase is a flavin enzyme that catalyzes the oxidation of monoamine neurotransmitters in the brain. Various toxic by-products, aldehydes and hydrogen peroxide produced during the catalytic process, can cause oxidative stress and neuronal cell death. Overexpression of MAO-B and insufficient dopamine concentration are recognized as pathological factors in neurodegenerative diseases (NDs) including Parkinson's disease (PD) and Alzheimer's disease (AD). Therefore, the inhibition of MAO-B is an attractive target for the treatment of NDs. Despite significant efforts, few selective and reversible MAO-B inhibitors have been clinically approved. Natural products have emerged as valuable sources of lead compounds in drug discovery. Compounds such as chromone, coumarin, chalcone, caffeine, and aurone, present in natural structures, are considered as privileged scaffolds in the synthesis of MAO-B inhibitors. In this review, we summarized the structure-activity relationship (SAR) of MAO-B inhibitors based on the naturally privileged scaffolds over the past 20 years. Additionally, we proposed a balanced discussion on the advantages and limitations of natural scaffold-based MAO-B inhibitors with providing a future perspective in drug development.

Cytogenotoxicity assessment of 3-(3,4-dihydroxyphenyl)-7,8-dihydroxycoumarin on HepG2/C3A cells and leukocytes

3-(3,4-Dihydroxyphenyl)-7,8-dihydroxycoumarin is a newly synthesized coumarin derivative with a potent antioxidant effect. The aim of the present study is to investigate the safety of this compound, determining the in vitro cytotoxic and genotoxic in human peripheral blood mononuclear cells (PBMC) and in HepG2/C3A cells. Cell viability has been investigated by the trypan blue staining test and MTT assay and the genotoxicity by the comet assay and micronucleus test, using concentrations between 0.01 and 10 μg/ml. The compound proved to be noncytotoxic in both cell lines, at all tested concentrations, protecting the cells from the DNA damage. In addition, this molecule does not show clastogenic/aneugenic effects when performing the micronucleus test with cytokinesis blockade. Based on the obtained data, and the conditions of the experiments, we can conclude that the 3-(3,4-dihydroxyphenyl)-7,8-dihydroxycoumarin is a safe molecule up to a concentration of 10 μg/ml, which encourages further studies aiming to explore its potential as a drug candidate.

Recent progress on small molecular temperature-sensitive fluorescent probes

Temperature is an important biophysical parameter that is closely related with the metabolic activity in living cells. Therefore, the detection of intracellular temperature changes is crucial for exploring temperature-related biological processes. Fluorescence probe is an ideal tool for observing temperature changes in cells, which has many advantages, such as high sensitivity, good selectivity, and noninvasive, and thus aroused the great interest of researchers. In this paper, we summarize the recent progress of organic small molecule temperature-sensitive fluorescence probes in recent years was reviewed. Particularly, we describe the common response mode to the temperature and the practical applications of the probe in living cells and even animal models. Moreover, an outlook regarding temperature detection in clinical applications is discussed. The temperature-sensitive fluorescent probe is a "black box" to many researchers. This review aims to open a window on the prospect of the noninvasive in vivo detection of temperature which is helpful to deeper understand this rich research area.

Design, Synthesis, and Pharmacological Evaluation of N-Propargylated Diphenylpyrimidines as Multitarget Directed Ligands for the Treatment of Alzheimer's Disease

Alzheimer's disease (AD), a multifactorial complex neural disorder, is categorized with progressive memory loss and cognitive impairment as main clinical features. The multitarget directed ligand (MTDL) strategy is explored for the treatment of multifactorial diseases such as cancer and AD. Herein, we report the synthesis and screening of 24 N-propargyl-substituted diphenylpyrimidine derivatives as MTDLs against acetylcholine/butyrylcholine esterases and monoamine oxidase enzymes. In this series, VP1 showed the most potent MAO-B inhibitory activity with an IC₅₀ value of 0.04 ± 0.002 μM. VP15 with an IC₅₀ value of 0.04 ± 0.003 μM and a selectivity index of 626 (over BuChE) displayed the most potent AChE inhibitory activity in this series. In the reactive oxygen species (ROS) inhibition studies, VP1 reduced intercellular ROS levels in SH-SY5Y cells by 36%. This series of compounds also exhibited potent neuroprotective potential against 6-hydroxydopamine-induced neuronal damage in SH-SY5Y cells with up to 90% recovery. In the in vivo studies in the rats, the hydrochloride salt of VP15 was orally administered and found to cross the blood-brain barrier and reach the target site. VP15·HCl significantly attenuated the spatial memory impairment and improved the cognitive deficits in the mice. This series of compounds were found to be irreversible inhibitors and showed no cytotoxicity against neuronal cells. In in silico studies, the compounds attained thermodynamically stable orientation with complete occupancy at the active site of the receptors. Thus, N-propargyl-substituted diphenylpyrimidines displayed drug-like characteristics and have the potential to be developed as MTDLs for the effective treatment of AD.

A multifunctional metal regulator as the potential theranostic agent: Design, synthesis, anti-AD activities and metallic ion sensing properties

Although there is no cure for Alzheimer's disease (AD) due to its complex pathogenesis, early detection and treatment can help delay the development of the disease. So, it is necessary to develop multifunctional metal regulators that can integrate the therapeutics and diagnostics effect against AD. In this work, N-(anthracene-9-ylmethylene)benzohydrazide (probe 1), a fluorescent probe with imine and carbonyl as chelating sites was designed and synthesized. Results showed that 1 had good activities related to AD, such as regulation of metal homeostasis, inhibition of β-amyloid (Aβ) aggregation and scavenging of reactive oxygen species. The selectivity experiment showed that probe 1 had a good recognition effect on Cu²⁺. Fluorescence imaging assay also indicated that probe 1 had a good fluorescence imaging effect on Cu²⁺ in living cells. Furthermore, probe 1 had showed no cytotoxicity and good BBB permeability. These results indicated that probe 1 had potential diagnostic and therapeutic capabilities, and can be used as the multifunctional theranostic agent for AD.

Natural source, bioactivity and synthesis of 3-Arylcoumarin derivatives

3-arylcoumarins with different pharmacological properties widely exist in a variety of natural plants. The extensive research on 3-arylcoumarins was attributed to its therapeutic and relatively easy isolation. Therefore, 3-arylcoumarins can be recognised as useful structures for the design of novel compounds with potential pharmacological interest, particularly in the fields of anti-inflammatory, anti-cancer, antioxidant, Monoamine oxidase (MAO) enzyme inhibition, etc. The current review highlights the biological activities, design, and chemical synthetic methods of 3-arylcoumarins derivatives as well as their important natural product sources.

3-Phenylcoumarins as a Privileged Scaffold in Medicinal Chemistry: The Landmarks of the Past Decade

3-Phenylcoumarins are a family of heterocyclic molecules that are widely used in both organic and medicinal chemistry. In this overview, research on this scaffold, since 2010, is included and discussed, focusing on aspects related to its natural origin, synthetic procedures and pharmacological applications. This review paper is based on the most relevant literature related to the role of 3-phenylcoumarins in the design of new drug candidates. The references presented in this review have been collected from multiple electronic databases, including SciFinder, Pubmed and Mendeley.

Determination of Antioxidant Activity by Oxygen Radical Absorbance Capacity (ORAC-FL), Cellular Antioxidant Activity (CAA), Electrochemical and Microbiological Analyses of Silver Nanoparticles Using the Aqueous Leaf Extract of Solanum mammosum L

PURPOSE

The importance of studying polyphenolic compounds as natural antioxidants has encouraged the search for new methods of analysis that are quick and simple. The synthesis of silver nanoparticles (AgNPs) using plant extracts has been presented as an alternative to determine the total polyphenolic content and its antioxidant activity.

METHODS

In this study, aqueous leaf extract of Solanum mammosum, a species of plant endemic to South America, was used to produce AgNPs. The technique of oxygen radical absorption capacity using fluorescein (ORAC-FL) was used to measure antioxidant activity. The oxidation of the 2´,7´-dichlorodihydrofluorescein diacetate (DCFH2-DA) as fluorescent probe was used to measure cellular antioxidant activity (CAA). Electrochemical behavior was also examined using differential pulse voltammetry (DPV) and cyclic voltammetry (CV). Total polyphenolic content (TPH) was analyzed using the Folin-Ciocalteu method, and the major polyphenolic compound was analyzed by high performance liquid chromatography with diode array detector (HPLC/DAD). Finally, a microbial analysis was conducted using Escherichia coli and Bacillus sp.

RESULTS

The average size of nanoparticles was 5.2 ± 2.3 nm measured by high-resolution transmission electron microscopy (HR-TEM). The antioxidant activity measured by ORAC-FL in the extract and nanoparticles were 3944 ± 112 and 637.5 ± 14.8 µM ET/g of sample, respectively. Cellular antioxidant activity was 14.7 ± 0.2 for the aqueous extract and 12.5 ± 0.2 for the nanoparticles. The electrochemical index (EI) was 402 μA/V for the extract and 324 μA/V for the nanoparticles. Total polyphenolic content was 826.6 ± 20.9 and 139.7 ± 20.9 mg EGA/100 g of sample. Gallic acid was the main polyphenolic compound present in the leaf extract. Microbiological analysis revealed that although leaf extract was not toxic for Escherichia coli and Bacillus sp., minor toxic activity for AgNPs was detected for both strains.

CONCLUSION

It is concluded that the aqueous extract of the leaves of S. mammosum contains nontoxic antioxidant compounds capable of producing AgNPs. The methods using AgNPs can be used as a fast analytical tool to monitor the presence of water-soluble polyphenolic compounds from plant origin. Analysis and detection of new antioxidants from plant extracts may be potentially applicable in biomedicine.

Coumarins as Tool Compounds to Aid the Discovery of Selective Function Modulators of Steroid Hormone Binding Proteins

Steroid hormones play an essential role in a wide variety of actions in the body, such as in metabolism, inflammation, initiating and maintaining sexual differentiation and reproduction, immune functions, and stress response. Androgen, aromatase, and sulfatase pathway enzymes and nuclear receptors are responsible for steroid biosynthesis and sensing steroid hormones. Changes in steroid homeostasis are associated with many endocrine diseases. Thus, the discovery and development of novel drug candidates require a detailed understanding of the small molecule structure–activity relationship with enzymes and receptors participating in steroid hormone synthesis, signaling, and metabolism. Here, we show that simple coumarin derivatives can be employed to build cost-efficiently a set of molecules that derive essential features that enable easy discovery of selective and high-affinity molecules to target proteins. In addition, these compounds are also potent tool molecules to study the metabolism of any small molecule.

Clathriolide from marine demosponge Clathria (Thalysias) vulpina (Lamarck, 1814): previously undescribed macrocylic lactone with attenuating potential against angiotensin converting enzyme

Angiotensin-I converting enzyme catalyses the rate-determined step of the conversion of angiotensin-I to angiotensin-II that narrows the blood vessels, and angiotensin-I converting enzyme inhibitors were recognised as important medications for hypertension-related diseases. Chemical investigation of angiotensin-I converting enzyme inhibitors from marine demospongiae Clathria (Thalysias) vulpina (family Microcionidae), resulted in a previously undescribed 22-membered macrocyclic lactone derivative, named as clathriolide. The studied compound showed potential angiotensin converting enzyme attenuation property (IC₅₀ 0.41 mM), which was comparable with the standard captopril (IC₅₀ 0.36 mM). Clathriolide revealed significantly greater antioxidant potentials against free radical species (IC₅₀ < 1 mM) in comparison with the standard α-tocopherol (IC₅₀ > 1.5 mM). Superior electronic characteristics (topological polar surface area > 100) coupled with relatively smaller binding energy and docking score of clathriolide with the aminoacyl residues of angiotensin-I converting enzyme (-11.5 and -12.2 kcal/mol, respectively) described its potential inhibitory property against angiotensin-I converting enzyme.

Discovery and optimization of 3-thiophenylcoumarins as novel agents against Parkinson's disease: Synthesis, in vitro and in vivo studies

Monoamine oxidase B (MAO-B) inhibitors are still receiving great attention as promising therapeutic agents for central nervous system disorders. This study explores, for the first time, the potential of 3-thiophenylcoumarins as in vitro and in vivo agents against Parkinsońs disease. Twelve compounds were synthesized via Perkin-Oglialoro reaction, and in vitro evaluation of six hydroxylated molecules was performed. MAO-A and MAO-B inhibition, DPPH scavenging and inhibition of ROS formation, neurotoxicity on motor cortex neurons and neuroprotection against H₂O₂, were studied. In vivo effect on locomotor activity using the open field test was also evaluated for the best candidate [3-(4'-bromothiophen-2'-yl)-7-hydroxycoumarin, 5], a potent, selective and reversible MAO-B inhibitor (IC₅₀ = 140 nM). This compound proved to have a slightly better in vivo profile than selegiline, one of the currently treatments for Parkinson's disease, in reserpinized mice pretreated with levodopa and benserazide. Results suggested that, comparing positions 7 and 8, substitution at position 7 of the coumarin scaffold is better for the enzymatic inhibition. However, the presence of a catechol at positions 7 and 8 exponentially increases the antioxidant potential and the neuroprotective properties. Finally, all the molecules present good theoretical physicochemical properties that make them excellent candidates for the optimization of a lead compound.

Synthesis of Coumarin Derivatives as Versatile Scaffolds for GSK-3β Enzyme Inhibition

BACKGROUND

Glycogen synthase kinase-3 (GSK-3) is involved in the phosphorylation and inactivation of glycogen synthase. GSK-3 inhibitors have been associated with a variety of diseases, including Alzheimer´s disease (AD), diabetes type II, neurologic disorders, and cancer. The inhibition of GSK-3β isoforms is likely to represent an effective strategy against AD.

OBJECTIVE

The present work aimed to design and synthesize coumarin derivatives to explore their potential as GSK-3β kinase inhibitors.

METHODS

The through different synthetic methods were used to prepare coumarin derivatives. The GSK-3β activity was measured through the ADP-Glo™ Kinase Assay, which quantifies the kinasedependent enzymatic production of ADP from ATP, using a coupled-luminescence-based reaction. A docking study was performed by using the crystallographic structure of the staurosporine/GSK-3β complex [Protein Data Bank (PDB) code: 1Q3D].

RESULTS

The eleven coumarin derivatives were obtained and evaluated as potential GSK-3β inhibitors. Additionally, in silico studies were performed. The results revealed that the compounds 5c, 5d, and 6b inhibited GSK-3β enzymatic activity by 38.97-49.62% at 1 mM. The other coumarin derivatives were tested at 1 mM, 1 µM, and 1 nM concentrations and were shown to be inhibitor candidates, with significant IC50 (1.224-6.875 µM) values, except for compound 7c (IC50 = 10.809 µM). Docking simulations showed polar interactions between compound 5b and Lys85 and Ser203, clarifying the mechanism of the most potent activity.

CONCLUSION

The coumarin derivatives 3a and 5b, developed in this study, showed remarkable activity as GSK-3β inhibitors.

Structure-Based Optimization of Coumarin hA3 Adenosine Receptor Antagonists

Adenosine receptors participate in many physiological functions. Molecules that may selectively interact with one of the receptors are favorable multifunctional chemical entities to treat or decelerate the evolution of different diseases. 3-Arylcoumarins have already been studied as neuroprotective agents by our group. Here, differently 8-substituted 3-arylcoumarins are complementarily studied as ligands of adenosine receptors, performing radioligand binding assays. Among the synthesized compounds, selective A₃ receptor antagonists were found. 3-(4-Bromophenyl)-8-hydroxycoumarin (compound 4) displayed the highest potency and selectivity as A₃ receptor antagonist (K_i = 258 nM). An analysis of its X-ray diffraction provided detailed information on its structure. Further evaluation of a selected series of compounds indicated that it is the nature and position of the substituents that determine their activity and selectivity. Theoretical modeling calculations corroborate and explain the experimental data, suggesting this novel scaffold can be involved in the generation of candidates as multitarget drugs.

Synthesis and biological evaluation of 3-arylcoumarins as potential anti-Alzheimer's disease agents

Alzheimer's disease, a neurodegenerative illness, has the extremely complex pathogenesis. Accumulating evidence indicates there is a close relationship between several enzymes and Alzheimer's disease. Various substituted 3-arylcoumarin derivatives were synthesised, and their in vitro activity, including cholinesterase inhibitory activity, monoamine oxidase inhibitory activity, and antioxidant activity were investigated. Most of the compounds exhibited high activity; therefore 3-arylcoumarin compounds have the potential as drug candidates for the treatment of Alzheimer's disease.

Synthesis of 4-aryl-1,2,3-triazolyl appended natural coumarin-related compounds with antiproliferative and radical scavenging activities and intracellular ROS production modification

Diverse natural coumarin-based compounds linked to aryl via a 1,2,3-triazole spacer with antiproliferative activity against K562 cells, radical scavenging activity and a decrease of ROS production were provided.

Synthesis, antioxidant and antichagasic properties of a selected series of hydroxy-3-arylcoumarins

Oxidative stress is involved in several parasitic diseases such as Chagas. Agents able to selectively modulate biochemical processes involved in the disease represent promising multifunctional agents for the delay or abolishment of the progression of this pathology. In the current work, differently substituted hydroxy-3-arylcoumarins are described, exerting both antioxidant and trypanocidal activity. Among the compounds synthesized, compound 8 showed the most interesting profile, presenting a moderate scavenging ability for peroxyl radicals (ORAC-FL=2.23) and a high degree of selectivity towards epimastigotes stage of the parasite T. cruzi (IC₅₀=1.31μM), higher than Nifurtimox (drug currently used for treatment of Chagas disease). Interestingly, the current study revealed that small structural changes in the hydroxy-3-arylcoumarin core allow modulating both activities, suggesting that this scaffold has desirable properties for the development of promising classes of antichagasic compounds.

Efficient Catalyst One-Pot Synthesis of 7-(Aryl)-10,10-dimethyl-10,11-dihydrochromeno[4,3-b]chromene-6,8(7H,9H)-dione Derivatives Complemented by Antibacterial Activity

The problem of bacteria resistance to many known agents has inspired scientists and researchers to discover novel efficient antibacterial drugs. Three rapid, clean, and highly efficient methods were developed for one-pot synthesis of 7-(aryl)-10,10-dimethyl-10,11-dihydrochromeno[4,3-b]chromene-6,8(7H,9H)-dione derivatives. Three components are condensed in the synthesis, 4-hydroxycoumarin, 5,5-dimethyl-1,3-cyclohexanedione, and aromatic aldehydes, using tetrabutylammonium bromide (TBAB), diammonium hydrogen phosphate (DAHP), or ferric chloride (FeCl₃), respectively. Each method has different reaction mechanisms according to the catalyst. The present methods have advantages, including one-pot synthesis, excellent yields, short reaction times, and easy isolation of product. All catalysts utilized in our study could be reused several times without losing their catalytic efficiency. All synthesized compounds were fully characterized and evaluated for their antibacterial activity.

Antioxidant Activities of 4-Methylumbelliferone Derivatives

The synthesis of derivatives of 4-Methylumbelliferone (4-MUs), which are structurally interesting antioxidants, was performed in this study. The modification of 4-Methylumbelliferone (4-MU) by different reaction steps was performed to yield the target compounds, the 4-MUs. The 4-MUs were characterized by different spectroscopic techniques (Fourier transform infrared; FT-IR and Nuclear magnetic resonance; NMR) and micro-elemental analysis (CHNS). The in vitro antioxidant activity of the 4-MUs was evaluated in terms of their free radical scavenging activities against 2,2-diphenyl-1-picrylhydrazyl (DPPH), Nitric oxide radical scavenging activity assay, chelating activity and their (FRAP) ferric-reducing antioxidant power, which were compared with a standard antioxidant. Our results reveal that the 4-MUs exhibit excellent radical scavenging activities. The antioxidant mechanisms of the 4-MUs were also studied. Density Function Theory (DFT)-based quantum chemical studies were performed with the basis set at 3-21G. Molecular models of the synthesized compounds were studied to understand the antioxidant activity. The electron levels, namely HOMO (highest occupied molecular orbital) and LUMO (lowest unoccupied molecular orbital), for these synthesized antioxidants were also studied.

Coumarin-Chalcone Hybrids as Peroxyl Radical Scavengers: Kinetics and Mechanisms

The primary antioxidant activity of coumarin-chalcone hybrids has been investigated using the density functional and the conventional transition state theories. Their peroxyl radical scavenging ability was studied in solvents of different polarity and taking into account different reaction mechanisms. It was found that the activity of the hybrids increases with the polarity of the environment and the number of phenolic sites. In addition, their peroxyl radical scavenging activity is larger than those of the corresponding nonhybrid coumarin and chalcone molecules. This finding is in line with previous experimental evidence. All the investigated molecules were found to react faster than Trolox with (•)OOH, regardless of the polarity of the environment. The role of deprotonation on the overall activity of the studied compounds was assessed. The rate constants and branching ratios for the reactions of all the studied compounds with (•)OOH are reported for the first time.

3-Amidocoumarins as Potential Multifunctional Agents against Neurodegenerative Diseases

Monoamine oxidase (MAO) generates reactive oxygen species (ROS), which cause neuronal cell death, causing neurodegeneration. Agents that are able to concurrently inhibit MAO and scavenge free radicals represent promising multifunctional neuroprotective agents that could be used to delay or slow the progression of neurodegenerative diseases. In this work, variously substituted 3-amidocoumarins are described that exert neuroprotection in vitro against hydrogen peroxide in rat cortical neurons, as well as antioxidant activity in a 1,1-diphenyl-2-picrylhydrazyl (DPPH⋅) radical scavenging assay. Selective and reversible inhibitors of the MAO-B isoform were identified. Interestingly, in the case of the 3-benzamidocoumarins, substitution at position 4 with a hydroxy group abolishes MAO-B activity, but the compounds remain active in the neuroprotection model. Further evaluation of 3-heteroarylamide derivatives indicates that it is the nature of the heterocycle that determines the neuroprotective effects. Evaluation in a parallel artificial membrane permeability assay (PAMPA) highlighted the need to further improve the blood-brain barrier permeability of this compound class. However, the compounds described herein adhere to Lipinski's rule of five, suggesting that this novel scaffold has desirable properties for the development of potential drug candidates.

Study of coumarin-resveratrol hybrids as potent antioxidant compounds

In the present work we synthesized a selected series of hydroxylated 3-phenylcoumarins 5–8, with the aim of evaluating in detail their antioxidant properties. From an in depth study of the antioxidant capacity data (ORAC-FL, ESR, CV and ROS inhibition) it was concluded that these derivatives are very good antioxidants, with very interesting profiles in all the performed assays. The study of the effect of the number and position of the hydroxyl groups on the antioxidant activity was the principal aim of this study. In particular, 7-hydroxy-3-(3'-hydroxy)phenylcoumarin (8) proved to be the most active and effective antioxidant of the selected series in four of the performed assays (ORAC-FL = 11.8, capacity of scavenging hydroxyl radicals = 54%, Trolox index = 2.33 and AI₃₀ index = 0.18). However, the presence of two hydroxyl groups on this molecule did not increase greatly the activity profile. Theoretical evaluation of ADME properties of all the derivatives was also carried out. All the compounds can act as potential candidates for preventing or minimizing the free radical overproduction in oxidative-stress related diseases. These preliminary findings encourage us to perform a future structural optimization of this family of compounds.

New insights into the antioxidant activity of hydroxycinnamic and hydroxybenzoic systems: spectroscopic, electrochemistry, and cellular studies

A series hydroxycinnamic and gallic acids and their derivatives were studied with the aim of evaluating their in vitro antioxidant properties both in homogeneous and in cellular systems. It was concluded from the oxygen radical absorbance capacity-fluorescein (ORAC-FL), 1,1-diphenyl-2-picrylhydrazyl (DPPH), and cyclic voltammetry data that some compounds exhibit remarkable antioxidant properties. In general, in homogeneous media (DPPH assay), galloyl-based cinnamic and benzoic systems (compounds 7-11) were the most active, exhibiting the lowest oxidation potentials in both dimethyl sulfoxide (DMSO) and phosphate buffer. Yet, p-coumaric acid and its derivatives (compounds 1-3) disclosed the highest scavenging activity toward peroxyl radicals (ORAC-FL assay). Interesting structure-property- activity relationships between ORAC-FL, or DPPH radical, and redox potentials have been attained, showing that the latter parameter can be a valuable antioxidant measure. It was evidenced that redox potentials are related to the structural features of cinnamic and benzoic systems and that their activities are also dependent on the radical generated in the assay. Electron spin resonance data of the phenoxyl radicals generated both in DMSO and phosphate buffer support the assumption that radical stability is related to the type of phenolic system. Galloyl-based cinnamic and benzoic ester-type systems (compounds 9 and 11) were the most active and effective compounds in cell-based assays (51.13 ± 1.27% and 54.90 ± 3.65%, respectively). In cellular systems, hydroxycinnamic and hydroxybenzoic systems operate based on their intrinsic antioxidant outline and lipophilic properties, so the balance between these two properties is considered of the utmost importance to ensure their performance in the prevention or minimization of the effects due to free radical overproduction.

Discovery of 3-Arylcoumarin-tetracyclic Tacrine Hybrids as Multifunctional Agents against Parkinson's Disease

A series of multifunctional directed 3-arylcoumarin-tetracyclic tacrine derivatives was designed and synthesized for the treatment of Parkinson's disease (PD). A number of derivatives (18, 19, 20, 21, and 24) demonstrated significant reduction of aggregation of "human" alpha-synuclein (α-synuclein) protein, expressing on transgenic Caenorhabditis elegans (C. elegans) model NL5901. Moreover, compounds 16, 18, and 24 also exhibited good antioxidant properties and significantly increased the dopamine (DA) content in N2 and NL5901 strains of C. elegans. Interestingly, the protective efficacy of these hybrids seems to be mediated via activation of longevity promoting transcription factor DAF-16. In addition, molecular modeling studies have evidenced the exquisite interaction of most active compounds 18 and 24 with α-synuclein protein. Taken together, the data indicate that the derivatives may be useful leads against aging and age associated PD.

Substituent position influence on the electrochemical properties and antioxidant activity of tetra(aminophenyl)porphyrins

Free radicals and reactive oxygen species (ROS) are important intermediate products in physiological processes. In the healthy cell, they are generated and regulated by enzymes and low molecular weight antioxidants. Overproduction of ROS leads to a large list of diseases, so the determination of antioxidant activity of perspective natural and synthetic compounds is necessary for drugs development. In this paper cyclic voltammetry (CV) method was applied to the electrochemical and superoxide scavenging properties of 5,10,15,20-tetrakis(4′-aminophenyl)porphyrin ( H 2 T (p- NH 2 Ph ) P ) and 5,10,15,20-tetrakis(3′-aminophenyl)porphyrin ( H 2 T (m- NH 2 Ph ) P ) investigation. It is shown that the studied porphyrins have very similar electrochemical behavior and slight effect on the quantity of superoxide produced during first CV cycle therefore the estimation of superoxide scavenging properties may be performed by the [Formula: see text] oxidation peak current monitoring. The antioxidant properties of porphyrins were estimated in terms of binding constants. The strong effect of NH 2 group position on the superoxide scavenging activity are shown: the H 2 T (p- NH 2 Ph ) P (kb = 12.7 × 102 mol-1) demonstrates the significant superoxide scavenging activities whereas H 2 T (m- NH 2 Ph ) P (kb = 0.83 × 102 mol-1) — negligible. The most probable mechanism of superoxide scavenges explaining the observed differences are the H -atoms transfer due to N – H bond breaking in the aminophenyl substituent.

Synthesis and evaluation of antioxidant and trypanocidal properties of a selected series of coumarin derivatives

This article describes the preparation and characterization of a selected series of coumarin derivatives with the aim of evaluating their antioxidant properties and their activity against Trypanosoma cruzi, the parasite responsible for Chagas disease. All the derivatives demonstrated moderate trypanocidal activity in the epimastigote and trypomastigote stages (clone Dm28c), with Compound 3 presenting the highest trypanocidal activity of the entire series, displaying higher activity than nifurtimox, which was used as a reference compound. In addition to the trypanocidal activity, this compound proved to have a very interesting antioxidant profile, as well as no cytotoxicity. These preliminary findings encouraged the authors to study the future structural optimization of this scaffold.

One-pot synthesis and radical scavenging activity of novel polyhydroxylated 3-arylcoumarins

An unexpected domino rearrangement brought about the development of a novel one-pot procedure for synthesis of coumarins. This protocol allowed the gram-scale synthesis of a variety of polyhydroxylated derivatives 3a-p, from readily available starting materials at a low cost. Based on two proven intermediates, a probable mechanism consisting of boron tribromide induced demethylation/lactone ring opening/elimination/isomerization/lactone ring closure reaction sequence of in situ formed 3-aryl-3,4-dihydroisocoumarin-4-carboxylic acids was deduced. Compared to the common methods, used for the synthesis of coumarins, the proposed herein possesses great advantages, such as mild conditions, good yields for short reaction time, simple work-up procedure and easy isolation of the final products. The structure of the newly synthesized compounds 3a-p was established by spectroscopic methods ((1)H NMR, (13)C NMR, IR, MS and HRMS) and their radical scavenging activity was evaluated in vitro against 1,1-diphenyl-2-picrylhydrazyl free radical (DPPH). The results obtained show that compounds 3g-p posses higher radical scavenging activity (3.16 ≤ SC50 [μM] ≤ 6.82) than well-known antioxidants such as trolox, protocatechuic acid, caffeic acid and gallic acid (SC50 [μM] = 9.34, 8.83, 9.48, 5.33, respectively), which is a precondition for promising antioxidant activity of these compounds to be expected.