Adenosine Receptor Ligands: Coumarin-Chalcone Hybrids as Modulating Agents on the Activity of hARs.

Adenosine receptors (ARs) play an important role in neurological and psychiatric disorders such as Alzheimer's disease, Parkinson's disease, epilepsy and schizophrenia. The different subtypes of ARs and the knowledge on their densities and status are important for understanding the mechanisms underlying the pathogenesis of diseases and for developing new therapeutics. Looking for new scaffolds for selective AR ligands, coumarin-chalcone hybrids were synthesized (compounds 1-8) and screened in radioligand binding (hA1, hA2A and hA3) and adenylyl cyclase (hA2B) assays in order to evaluate their affinity for the four human AR subtypes (hARs). Coumarin-chalcone hybrid has been established as a new scaffold suitable for the development of potent and selective ligands for hA1 or hA3 subtypes. In general, hydroxy-substituted hybrids showed some affinity for the hA1, while the methoxy counterparts were selective for the hA3. The most potent hA1 ligand was compound 7 (Ki = 17.7 µM), whereas compound 4 was the most potent ligand for hA3 (Ki = 2.49 µM). In addition, docking studies with hA1 and hA3 homology models were established to analyze the structure-function relationships. Results showed that the different residues located on the protein binding pocket could play an important role in ligand selectivity.

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 (Ki = 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.

Design, Synthesis and Characterization of Covalent KDM5 Inhibitors.

Histone lysine demethylases (KDMs) are involved in the dynamic regulation of gene expression and they play a critical role in several biological processes. Achieving selectivity over the different KDMs has been a major challenge for KDM inhibitor development. Here we report potent and selective KDM5 covalent inhibitors designed to target cysteine residues only present in the KDM5 sub-family. The covalent binding to the targeted proteins was confirmed by MS and time-dependent inhibition. Additional competition assays show that compounds were non 2-OG competitive. Target engagement and ChIP-seq analysis showed that the compounds inhibited the KDM5 members in cells at nano- to micromolar levels and induce a global increase of the H3K4me3 mark at transcriptional start sites.

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.

Facing Chagas' disease: trypanocidal properties of new coumarin-chalcone scaffolds.

With the aim of finding new chemical entities based on coumarin and chalcone scaffolds, new hybrid compounds 2-5 were designed and synthesized. The trypanocidal activity of these compounds was tested against the epimastigote, trypomastigote and amastigote stages of the Trypanosoma cruzi parasite. Cytotoxicity assays were also performed in RAW 264.7 and VERO cells. Compound 5 presented the highest trypanocidal activity of the series, with trypanocidal values higher than nifurtimox for the trypomastigote and epimastigote stages., but presenting cytotoxic effects in the mammalian cells. A SAR study suggested that methoxy substitution at positions 2 and 5 in the designed scaffold seemed to be a key feature for the trypanocidal activity. Therefore, the coumarin-chalcone scaffold can be taken into account for further lead optimization and design new and more effective trypanocidal compounds.

Design, synthesis and antibacterial study of new potent and selective coumarin-chalcone derivatives for the treatment of tenacibaculosis.

With the aim of finding new chemical entities selective for fish pathogens to avoid drug resistance in humans, a series of coumarin-chalcone hybrid compounds with different patterns of substitution were designed and synthesized. Their antibacterial activity was evaluated against important types of human bacteria strains (Escherichia coli, Staphylococcus aureus and Pseudomonas aeruginosa) and against a fourteen strains of the marine pathogen Tenacibaculum maritimum, responsible for tenacibaculosis in fish, which is an important disease that causes great economical loss in the aquaculture industry. All the amino derivatives 5-12 presented high activity against different strains of T. maritimum, no activity against any of the three human pathogenic bacteria strains and no toxicity. Compounds 6, 7 and 11 were the most promising molecules. The most sensitive strains to these compounds were LL01 8.3.8 and LL01 8.3.1, being compound 11 up to 20 times more active than enrofloxacin. Therefore these scaffolds are good candidates for aquaculture treatments, avoiding possible drug resistance problems in humans.

Synthesis and pharmacological activities of non-flavonoid chromones: a patent review (from 2005 to 2015).

INTRODUCTION: Chromones are one of the major classes of naturally occurring compounds. Their chemistry has been widely explored and extensively reviewed. The following review intends to give a broad overview of the patented chromones. Particular attention has been given to their synthesis, uses and applications in last 10 years. AREAS COVERED: The authors provide an overview of the recent scientific reports describing the obtaining and study of new chromones. The review emphasizes the rationale behind natural sources, synthesis, biological activities and structure-activity relationships of the new chromone derivatives. The article is based on the literature published from 2005 to 2015 related to the development of this family of compounds. The patents presented in this review have been collected from multiple electronic databases including SciFinder, Espacenet and Mendeley. EXPERT OPINION: Although a great number of chromones have been published in bibliographic sources in the last years, there is little innovation in the synthetic methodologies. Some natural sources and isolation techniques were described. Different pharmacological applications have also been claimed. Two of the most studied applications have been the use of these compounds as therapeutic agents for cancer and skin diseases. Some safety requirements need to be developed in order to find new chemical entities as new drugs.

Development of novel adenosine receptor ligands based on the 3-amidocoumarin scaffold.

With the aim of finding new adenosine receptor (AR) ligands presenting the 3-amidocoumarin scaffold, a study focusing on the discovery of new chemical entities was carried out. The synthesized compounds 1-8 were evaluated in radioligand binding (A1, A2A and A3) and adenylyl cyclase activity (A2B) assays in order to determine their affinity for human AR subtypes. The 3-benzamide derivative 4 showed the highest affinity of the whole series and was more than 30-fold selective for the A3 AR (Ki=3.24 µM). The current study supported that small structural changes in this scaffold allowed modulating the affinity resulting in novel promising classes of A1, A2A, and/or A3 AR ligands. We also performed docking calculations in hA2A and hA3 to identify the hypothetical binding mode for the most active compounds. In addition, some ADME properties were calculated in order to better understand the potential of these compounds as drug candidates.

Bioactive Coumarins from Marine Sources: Origin, Structural Features and Pharmacological Properties.

Nature is an ancient pharmacy that is largely used as an inspiring source for drug discovery processes for the early eras. Several drugs used nowadays are of natural product origin or inspired on the basis of natural product structures and approximately half of the 20 best-selling non-protein drugs are related to natural products. However, a largely unexplored marine world that presumably harbors the most biodiversity may be the vastest resource to discover compounds with remarkable biological properties. Marine based drug discovery research has been mainly focused on crude extracts. The purpose of this review is to summarize the findings reported in this area, particularly focuses on marine-derived coumarincontaining compounds.

Interest of antioxidant agents in parasitic diseases. The case study of coumarins.

Tropical parasitic diseases, especially those produced by protozoan parasites, are a major public health problem in many countries, and their impact in the health burden is significant. Oxidative processes proved to be related to these diseases, being the antioxidant agents promising therapeutic solutions for them. Therefore, this review provides an overview of published manuscripts regarding both activities. In particular, the interest of the coumarin derivatives as antioxidant agents with application in parasitic diseases is discussed in this manuscript. The recent findings in this field are highlighted.

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.

Potential pharmacological uses of chalcones: a patent review (from June 2011 - 2014).

INTRODUCTION: Chalcones are one of the major classes of naturally occurring compounds. A large number of synthetic routes have been reported for the synthesis of chalcones, the most classical and general being the Claisen-Schmidt condensation. Chalcones and their derivatives have a huge importance in medicinal chemistry, displaying a wide range of important pharmacological activities. AREAS COVERED: The authors provide an overview of the recent scientific reports describing the obtention and study of new chalcones. The review emphasizes the rationale behind the natural sources, the discovery, the design, the synthesis, the biological activities and the study of structure-activity relationships of the new chalcone derivatives. The article is based on the literature published from June 2011 - 2014 related to the development of this family of compounds. The patents presented in this review have been collected from multiple electronic databases including Scifinder, Espacenet and Mendeley. EXPERT OPINION: Although a great number of extracts containing chalcones have been published in bibliographic sources, the potential of this scaffold could be deeply studied in many different areas in which almost nothing has been described. A lot of work should be done to reach the potency and safety requirements needed to develop new chemical entities as new drugs.

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.

Diastereospecific nazarov cyclization of fully substituted dienones: generation of vicinal all-carbon-atom quaternary stereocenters.

No vacancy: Fully substituted dienones that are highly polarized by a vinylogous carbonate group were found to undergo a remarkably rapid and diastereospecific Nazarov cyclization that led to cyclopentenones with vicinal all-carbon-atom quaternary centers (see example; SEM=2-(trimethylsilyl)ethoxymethyl, Tf=trifluoromethanesulfonyl).

Synthesis and electrochemical and biological studies of novel coumarin-chalcone hybrid compounds.

A series of novel hydroxy-coumarin-chalcone hybrid compounds 2a-i has been synthesized by employing a simple and efficient methodology. An electrochemical characterization using cyclic voltammetry and ESR spectroscopy were carried out to characterize the oxidation mechanism for the target compounds. The antioxidant capacity and reactivity were determined by ORAC and ESR assays, respectively. Biological assays were assessed to evaluate the cytotoxicity and cytoprotection capacity against ROS/RNS on BAEC. The results revealed that all tested compounds present ORAC values that are much higher than other well-known antioxidant compounds such as quercetin and catechin. Compound 2e showed the highest ORAC value (14.1) and also presented a low oxidation potential, good scavenging capacity against hydroxyl radicals, low cytotoxicity, and high cytoprotective activity.

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

In the present work we synthesized a series of hydroxy-3-arylcoumarins (compounds 1-9), some of them previously described as MAO-B selective inhibitors, with the aim of evaluating their antioxidant properties. Theoretical evaluation of ADME properties of all the derivatives was also carried out. From the ORAC-FL, ESR and CV data it was concluded that these derivatives are very good antioxidants, with a very interesting hydroxyl, DPPH and superoxide radicals scavenging profiles. In particular compound 9 is the most active and effective antioxidant of the series (ORAC-FL=13.5, capacity of scavenging hydroxyl radicals=100%, capacity of scavenging DPPH radicals=65.9% and capacity of scavenging superoxide radicals=71.5%). Kinetics profile for protection fluorescein probe against peroxyl radicals by addition of antioxidant molecule 9 was also performed. Therefore, it can operate as a potential candidate for preventing or minimizing the free radicals overproduction in oxidative-stress related diseases.

Chalcone-based derivatives as new scaffolds for hA3 adenosine receptor antagonists.

OBJECTIVES: With the aim of finding new adenosine receptor (AR) ligands based on the chalcone scaffold, we report the synthesis of a new series of coumarin-chalcone hybrids and the pharmacological characterization of their actions at four subtypes of AR. METHODS: The synthesized compounds 5-10 were characterized in radioligand binding (A1 , A2A and A3 ) and adenylyl cyclase activity assays (A2B ) to determine the affinity of the compounds for the four human AR (hAR) subtypes. KEY FINDINGS: Coumarin-chalcone hybrids were found to be ligands with a novel structure, not reported thus far, that showed varying affinity and selectivity for AR subtypes. CONCLUSIONS: The coumarin-chalcone hybrids in which ring B of the chalcone scaffold was a thiophene (compounds 5 and 9) were found to be the most potent compounds of the series. Compound 9, in which ring A of the chalcone moiety was the phenyl ring of the coumarin, showed similar activity against hA1 , hA2A and hA3 ARs, while compound 5, in which ring A of the chalcone was substituted by the benzopyrone ring of the coumarin moiety, showed similar activity only at the hA3 AR and, therefore, was deemed to be selective (Ki (dissociation constant) = 5160 nm).

3-(4-Meth-oxy-benzo-yl)-6-nitro-coumarin.

In the title coumarin derivative (also known as 2H-chromen-2-one or 2H-1-benzopyran-2-one), C17H11NO6, the coumarin ring system is nearly planar, with a dihedral angle of 3.35 (9)° between the pyrone and the benzene rings. The dihedral angle between the planes formed by the coumarin ring system and the benzene substituent is 54.60 (7)°, clearly showing the non-coplanarity of the whole aromatic system. The crystal studied was a non-merohedral twin; the minor component refined to approximately 0.44.

Synthesis and structure-activity relationships of novel amino/nitro substituted 3-arylcoumarins as antibacterial agents.

A new series of amino/nitro-substituted 3-arylcoumarins were synthesized and their antibacterial activity against clinical isolates of Staphylococcus aureus (Gram-positive) and Escherichia coli (Gram-negative) was evaluated. Some of these molecules exhibited antibacterial activity against S. aureus comparable to the standards used (oxolinic acid and ampicillin). The preliminary structure-activity relationship (SAR) study showed that the antibacterial activity against S. aureus depends on the position of the 3-arylcoumarin substitution pattern. With the aim of finding the structural features for the antibacterial activity and selectivity, in the present manuscript different positions of nitro, methyl, methoxy, amino and bromo substituents on the 3-arylcoumarin scaffold were reported.

Focusing on new monoamine oxidase inhibitors: differently substituted coumarins as an interesting scaffold.

It is commonly accepted that monoamine oxidase (MAO) may play a critical role in the regulation of the central nervous system activity and contribute to the pathogenesis of human neurodegenerative and depressive disorders. This has encouraged an active research in the development of new drugs, MAO inhibitors, since they may represent an important advance in the treatment of complex diseases such as Alzheimer and Parkinson, which are becoming prevalent pathologies due to the increase of aging population of developed countries societies. Different research groups are intensively working in this area with the aim of finding new MAO selective inhibitors. Differently substituted coumarins have been synthesized and evaluated as MAO-A and MAO-B inhibitors. The purpose of this review is to summarize the findings reported in this area, particularly focuses on the coumarin scaffold.