Chromone Ring Research Articles

Improvement of the solubility and anticancer activity of 6,8-dibromochrysin by encapsulation into β-cyclodextrin and its derivatives

Background6,8-dibromochrysin (BrCN), a halogenated chrysin, possesses a profound bioactivity against dengue and Zika viruses and various types of cancer. However, the pharmaceutical applications of BrCN are limited by its poor aqueous solubility. MethodsMolecular encapsulation of BrCN with beta-cyclodextrin (βCD) and its derivatives—2,6-di-O-methyl-beta-cyclodextrin (DMβCD) and 2-hydroxypropyl-beta-cyclodextrin (HPβCD)—was performed to enhance its water solubility, and the resulting inclusion complexes were characterized theoretically and experimentally. Significant findingsMolecular docking showed that BrCN adopted two possible orientations, namely chromone ring insertion (C-form) and phenyl ring insertion (P-form) inside the lipophilic cavities of βCD, DMβCD, and HPβCD. Molecular dynamics (MD) simulations and the molecular mechanics with generalized Born and surface area solvation (MM-GBSA) method suggested that βCD derivatives show better BrCN-encapsulating potential as evidenced by their lower binding free energy values. Phase solubility study indicated a 1:1 stoichiometry between BrCN and the hosts (AL type). The resulting inclusion complexes were characterized using scanning electron microscopy and differential scanning calorimetry. We noted that encapsulation with βCD, DMβCD, and HPβCD resulted in an approximately 27-fold, 92-fold and 104-fold increase in the aqueous solubility of BrCN, respectively and enhanced its anticancer activity against A549 and H1975 cancer cells.

Channel activity of SARS-CoV-2 viroporin ORF3a inhibited by adamantanes and phenolic plant metabolites

SARS-CoV-2 has been responsible for the major worldwide pandemic of COVID-19. Despite the enormous success of vaccination campaigns, virus infections are still prevalent and effective antiviral therapies are urgently needed. Viroporins are essential for virus replication and release, and are thus promising therapeutic targets. Here, we studied the expression and function of recombinant ORF3a viroporin of SARS-CoV-2 using a combination of cell viability assays and patch-clamp electrophysiology. ORF3a was expressed in HEK293 cells and transport to the plasma membrane verified by a dot blot assay. Incorporation of a membrane-directing signal peptide increased plasma membrane expression. Cell viability tests were carried out to measure cell damage associated with ORF3a activity, and voltage-clamp recordings verified its channel activity. The classical viroporin inhibitors amantadine and rimantadine inhibited ORF3a channels. A series of ten flavonoids and polyphenolics were studied. Kaempferol, quercetin, epigallocatechin gallate, nobiletin, resveratrol and curcumin were ORF3a inhibitors, with IC50 values ranging between 1 and 6 µM, while 6-gingerol, apigenin, naringenin and genistein were inactive. For flavonoids, inhibitory activity could be related to the pattern of OH groups on the chromone ring system. Thus, the ORF3a viroporin of SARS-CoV-2 may indeed be a promising target for antiviral drugs.

Cascade in Situ Iodination, Chromone Annulation, and Cyanation for Site-Selective Synthesis of 2-Cyanochromones.

A facile cascade reaction for the site selective synthesis of 2-cyanochromones is described. By using simple o-hydroxyphenyl enaminones and potassium ferrocyanide trihydrate (K4[Fe(CN)6]3·3H2O) as starting materials and I2/AlCl3 as promoters, the products are furnished via tandem chromone ring formation and C-H cyanation. The in situ formation of 3-iodochromone and a formal 1,2-hydrogen atom transfer (HAT) process account for the unconventional site selectivity. In addition, the synthesis of 2-cyanoquinolin-4-one has been realized by employing corresponding 2-aminophenyl enaminone as substrate.

Recyclization of morpholinochromonylidene-thiazolidinone using nucleophiles: facile synthesis, cytotoxic evaluation, apoptosis, cell cycle and molecular docking studies of a novel series of azole, azine, azepine and pyran derivatives.

A convenient synthetic approach for construction of a novel series of substituted azoles, azines, azepines and pyrans clubbed with a morpholinothiazolidinone hybrid was achieved. The methodology depended on ring-opening and ring-closure (RORC) of chromone ring in 2-(morpholinoimino)-5-[(4-oxo-4H-chromen-3-yl)methylene]-3-phenylthiazolidin-4-one (3) through its reaction with a series of nitrogen and carbon nucleophiles under mild reaction conditions. The cytotoxic effects of all products were evaluated against three cancerous cell lines (MCF-7, HepG-2 and SKOV-3) by the standard SRB method. Fortunately, the products 7, 11, 12, 15, 19, 22, 26 and 28 were found to be the most active against all cancer cell lines, comparable to doxorubicin. Apoptosis was determined using flow cytometry along with cell cycle analysis and supported by molecular docking. The products 7, 11, 12, 15, 19, 22, 26 and 28 induced a significant early-and late-apoptotic effect against all tumor cells. In addition, these products preferred to arrest all cancer cells in the G1 and G2 phases. Finally, molecular docking was attempted to investigate the binding mode of products 12 and 22 with p53-MDM2 protein receptor.

Access to Sulfur-Containing Bisheterocycles through Base-Promoted Consecutive Tandem Cyclization/Sulfenylation with Elemental Sulfur.

A convenient and efficient tandem cyclization/sulfenylation of o-alkynyl-phenols/-anilines/enaminones for the synthesis of diverse sulfur-containing bisheterocycles has been developed using stable, odorless, and easy-to-handle elemental S8 as a building block under green chemistry conditions. Notably, a one-step simple base-mediated organic transformation affords a benzofuran (indole or chromone) ring and two C-S bonds. Attractive features of this methodology include the absence of a metal catalyst, mild conditions, good functional group tolerance, and valuable product structures.

Synthesis of functionalized flavones from 3-halo-2-(methylthio)-4H-chromen-4-ones

A simple and efficient method for the synthesis of flavones was achieved by selective sulfide Liebeskind-Srogl cross-coupling reaction of 2-(methylthio)-4H-chromen-4-ones and 3-halo-2-(methylthio)-4H-chromen-4-ones with arylboronic acids. This method is the first example of employing Liebeskind-Srogl coupling for the synthesis of flavones. Various aryl groups can be directly installed to the chromone ring. The structure of all the synthesized compounds were assigned by spectroscopic analysis.

An effective green one-pot synthesis of some novel 5-(thiophene-2-carbonyl)-6-(trifluoromethyl)pyrano[2,3-c]pyrazoles and 6-(thiophene-2-carbonyl)-7-(trifluoromethyl)pyrano[2,3-d]pyrimidines bearing chromone ring as anticancer agents

An effective green one-pot and catalyst-free synthesis of a series of novel 5-(thiophene-2-carbonyl)-6-(trifluoromethyl)pyrano[2,3-c]pyrazoles and 6-(thiophene-2-carbonyl)-7-(trifluoromethyl)pyrano[2,3-d]pyrimidines bearing chromone ring was achieved. The method depended on a one-pot three-component reaction of readily available starting materials 4-oxo-4H-chromene-3-carboxaldehyde, 2-thenoyltrifluoroacetone, and cyclic active methylene compounds in water as solvent. The targeted compounds were assessed for their in vitro anticancer activity against mammary gland breast cancer cell line (MCF-7), liver cancer (HepG-2), and human colon cancer (HCT-116) by using sulphorhodamine B assay (SRB) method, while doxorubicin, was utilized as standard reference drug. Compounds 4a, 4c, and 6b exhibited excellent anticancer activity versus all cancer cell lines with IC50 values ranging from 1.7 to 9.9 μg/mL.

Transition‐Metal‐Free C(sp2)‐H Dithiocarbamation and Chromone Annulation Cascade for 3‐Dithiocarbamyl Chromone Synthesis

AbstractThe transition‐metal‐free synthesis of 3‐dithiocarbamyl chromones by reacting o‐hydroxyphenylenaminones with thiurams in the presence of KIO3 and TEMPO is reported. In addition, the 3‐dithiocarbamyl chromones synthesized herein have been successfully utilized as starting materials in the synthesis of 3‐dithiocarbamyl pyrimidines and 3‐(benzylthio)chromones via featured chromone ring opening and C−S bond cleavage, respectively.magnified image

Experimental and theoretical electronic absorption spectra, optical, photoelectrical characterizations of 1, 2, 3-Thiazaphosphinine and 1, 2-Azaphospholes bearing a chromone ring: Solvatochromic effect and TD/DFT approach

Geometry, global energetic and dipole moment of the studied structures 1-4 in the ground state are calculated using the DFT/B3LYB/6-311++G (d,p) level of theory. It has been uncovered that compounds containing 1, 2, 3-thiazaphosphinine and 1, 2-azaphospholes bearing a Chromone ring structure displays noteworthy biological properties. The studied compounds 1-4 are non-planar, as indicated from the dihedral angles. Using frontier molecular orbital (FMO) analysis, various spectroscopic and quantum chemical parameters are evaluated. Besides, absorption energies, oscillator strength, and electronic transitions of 1, 2, 3-thiazaphosphinine and 1, 2-azaphospholes 1-4 molecules have been derived at TD-DFT/CAM-B3LYP/6-311++G (d, p) computations utilizing a PCM and measured in different solvents polar and non-polar experimentally in Uv-Vis spectra. The second-order perturbation interactions between donor and acceptor MOs of the ground state and the natural bond orbital (NBO) analysis show a localization and delocalization of electron density, intermolecular Charge Transfer CT character of n-π*, π-π* transitions. The calculated at the same level of theory which NLO, α, Δα and first order β were showed promising optical properties. For the understanding of reactivity points, the molecular electrostatic potential surfaces (MEPS) plots have been computed. All the calculations have been performed in the gas phase.

Myricetin Inhibits SARS-CoV-2 Viral Replication by Targeting Mpro and Ameliorates Pulmonary Inflammation.

The coronavirus disease 2019 (COVID-19) has spread widely around the world and has seriously affected the human health of tens of millions of people. In view of lacking anti-virus drugs target to SARS-CoV-2, there is an urgent need to develop effective new drugs. In this study, we reported our discovery of SARS-CoV-2 Mpro inhibitors. We selected 15 natural compounds, including 7 flavonoids, 3 coumarins, 2 terpenoids, one henolic, one aldehyde and one steroid compound for molecular docking and enzymatic screening. Myricetin were identified to have potent inhibit activity with IC50 3.684 ± 0.076 μM in the enzyme assay. The binding pose of Myricetin with SARS-CoV-2 Mpro was identified using molecular docking method. In the binding pocket of SARS-CoV-2 Mpro, the chromone ring of Myricetin interacts with His41 through π-π stacking, and the 3’-, 4’- and 7-hydroxyl of Myricetin interact with Phe140, Glu166and Asp187 through hydrogen bonds. Significantly, our results showed that Myricetin has potent effect on bleomycin-induced pulmonary inflammation by inhibiting the infiltration of inflammatory cells and the secretion of inflammatory cytokines IL-6, IL-1α, TNF-α and IFN-γ. Overall, Myricetin may be a potential drug for anti-virus and symptomatic treatment of COVID-19.

An efficient one pot I2/DMSO mediated synthesis and molecular modeling of novel fused pyrimidine‐chromone hybrids bearing potential antibacterial and antifungal pharmacophores sites

AbstractA series of novel ethyl‐l, 1, 2, 3, 6‐tetrahydro‐4‐methyl‐1‐(6‐methyl‐4‐oxo‐4H‐chromene‐2‐yl)‐2‐oxo/thioxo‐6‐phenyl pyrimidine‐5‐carboxylate compounds (2a–2k) were synthesized using I2/DMSO as a competent and cost‐effective catalyst in one pot green solvent system from corresponding chalcones (1a–1k) in better yields. IR, 1H‐NMR, 13C‐NMR, Mass, and X‐ray diffraction spectroscopic techniques were used for the characterization of newly synthesized compounds. All the compounds were tested for in‐vitro antibacterial activities against gram‐positive and gram‐negative bacteria like Staphylococcus aureus, Salmonella abony, Staphylococcus epidermidis, and Escherichia coli. Antifungal activities were also performed against Candida albicans and Aspergilus niger. It was found that the presence of electron withdrawing group on the aromatic ring attached to chromone ring increases the antibacterial activities (2g, 2h, and 2k); while the presence of electron releasing groups decreases activities. The presence of electron donating groups (─OCH3, ─Cl), on the phenyl ring attached to pyrimidine skeleton influenced negatively for the antibacterial activities.

Synthesis and biological evaluation of 3-styrylchromone derivatives as selective monoamine oxidase B inhibitors

A series of 3-styrylchromone derivatives was synthesized and evaluated for monoamine oxidase (MAO) A and B inhibitory activities. Most of all derivatives inhibited MAO-B selectively, except compound 21. Compound 19, which had a methoxy group at R2 on the chromone ring and chlorine at R4 on phenyl ring, potently inhibited MAO-B, with an IC50 value of 2.2 nM. Compound 1 showed the highest MAO-B selectivity, with a selectivity index of >3700. Further analysis of these compounds indicated that compounds 1 and 19 were reversible and mixed-type MAO-B inhibitors, suggesting that their mode of action may be through tight-binding inhibition to MAO-B.Quantitative structure–activity relationship (QSAR) analyses of the 3-styrylchromone derivatives were conducted using their pIC50 values, through Molecular Operating Environment (MOE) and Dragon. There were 1796 descriptors of MAO-B inhibitory activity, which showed significant correlations (P < 0.05). Further investigation of the 3-styrylchromone structures as useful scaffolds was performed through three-dimensional-QSAR studies using AutoGPA, which is based on the molecular field analysis algorithm using MOE. The MAO-B inhibitory activity model constructed using pIC50 value index exhibited a determination coefficients (R2) of 0.972 and a Leave-One-Out cross-validated determination coefficients (Q2) of 0.914.These data suggest that the 3-styrylchromone derivatives assessed herein may be suitable for the design and development of novel MAO inhibitors.

Synthesis, spectroscopic/electrochemical characterization, DNA/Protein binding studies and bioactivity assays of Ru(II) carbonyl complexes of 4-oxo-4H-chromene-3-carbaldehyde thiosemicarbazones

Four Ru(II) carbonyl complexes of 4-oxo-4H-chromene-3-carbaldehyde thiosemicarbazones (C1-C4) were synthesized and characterized through spectroscopic techniques. The coordination behaviour of the ligands to the metal ion was confirmed by solving the single crystal X-ray structure of a representative complex C4, in which the ligand showed coordination via the C2 carbon of the chromone ring, the azomethine nitrogen and thiolate sulfur. The interaction with DNA and protein showed a good binding profile of the complexes. Antimicrobial effects of the complexes were tested against bacterial and fungal strains, for which a significant activity was observed. Furthermore, MTT assay on A549 and MCF-7 cell lines indicated the cytotoxic potential of the synthesized complexes, overcoming the cisplatin activity under similar experimental conditions.

Effect of Water Microsolvation on the Excited-State Proton Transfer of 3-Hydroxyflavone Enclosed in γ-Cyclodextrin.

The effect of microsolvation on excited-state proton transfer (ESPT) reaction of 3-hydroxyflavone (3HF) and its inclusion complex with γ-cyclodextrin (γ-CD) was studied using computational approaches. From molecular dynamics simulations, two possible inclusion complexes formed by the chromone ring (C-ring, Form I) and the phenyl ring (P-ring, Form II) of 3HF insertion to γ-CD were observed. Form II is likely more stable because of lower fluctuation of 3HF inside the hydrophobic cavity and lower water accessibility to the encapsulated 3HF. Next, the conformation analysis of these models in the ground (S0) and the first excited (S1) states was carried out by density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations, respectively, to reveal the photophysical properties of 3HF influenced by the γ-CD. The results show that the intermolecular hydrogen bonding (interHB) between 3HF and γ-CD, and intramolecular hydrogen bonding (intraHB) within 3HF are strengthened in the S1 state confirmed by the shorter interHB and intraHB distances and the red-shift of O–H vibrational modes involving in the ESPT process. The simulated absorption and emission spectra are in good agreement with the experimental data. Significantly, in the S1 state, the keto form of 3HF is stabilized by γ-CD, explaining the increased quantum yield of keto emission of 3HF when complexing with γ-CD in the experiment. In the other word, ESPT of 3HF is more favorable in the γ-CD hydrophobic cavity than in aqueous solution.

Synthetic Methods for Phosphorus Compounds Containing Chromone and Thiochromone Rings

Synthetic Methods for Phosphorus Compounds Containing Chromone and Thiochromone Rings

Chemoselective synthesis of 3-trifluoromethylpyrazole-deoxybenzoin hybrids

A simple method of the synthesis of α-(3(5)-trifluoromethylpyrazol-5(3)-yl)-2-hydroxydeoxybenzoins by a chemoselective reaction of 2-(1,1,1-trifluoroacetonyl)chromones with hydrazine dihydrochloride was developed. This approach involves the initial attack of hydrazine at the carbonyl atom of the CF3C(O)CH2 group followed by the chromone ring opening at C-2 atom and subsequent cyclization to pyrazoles. Such synthetic strategy provides easy access to the novel type of pharmaceutically attractive 3-(trifluomethyl)pyrazole-deoxybenzoin hybrids in high yields.

Syntheses and Evaluation of 2- or 3-(N-Cyclicamino)chromone Derivatives as Monoamine Oxidase Inhibitors.

A series of 2-(N-cyclicamino)chromone derivatives (1a-4c) and 3-(N-cyclicamino)chromone derivatives (5a-8c) were synthesized, and their monoamine oxidase (MAO) A and B inhibitory activities were studied as part of a structure-activity relationship investigation. Compounds 1a-4c showed no remarkable inhibition for MAO-A or MAO-B, whereas compounds 5a-8c (with a few exceptions) showed significant and selective inhibition of MAO-B. Of these compounds, 7c, 7-methoxy-3-(4-phenyl-1-piperazinyl)-4H-1-benzopyran-4-one inhibited MAO-B the most potently and selectively, having IC50 of 15 nM and an MAO-B selectivity index of more than 6700; c.f, 50 nM and 2000, respectively, for safinamide. The mode of inhibition of 7c to MAO-B was competitive and reversible. Considering the IC50 values and selectivity indices of the other synthetic compounds, the presence of the methoxy group on the chromone ring (R2) of 7c seemed to increase MAO-B inhibition. Molecular docking analysis also supports this hypothesis. Our results suggest that 3-(N-cyclicamino)chromones are useful lead compounds for the development of MAO-B inhibitors.

Single Crystal X-Ray Structure for the Disordered Two Independent Molecules of Novel Isoflavone: Synthesis, Hirshfeld Surface Analysis, Inhibition and Docking Studies on IKKβ of 3-(2,3-dihydrobenzo[b][1,4]dioxin-6-yl)-6,7-dimethoxy-4H-chromen-4-one

The structure of the isoflavone compound, 3-(2,3-dihydrobenzo[b][1,4]dioxin-6-yl)-6,7-dimethoxy-4H-chromen-4-one (5), was elucidated by 2D-NMR spectra, mass spectrum and single crystal X-ray crystallography. Compound 5, C19H16O6, was crystallized in the monoclinic space group P21/c with the cell parameters; a = 12.0654(5) Å, b =11.0666(5) Å, c = 23.9550(11) Å, β = 101.3757(16)°, V = 3135.7(2) Å3, and Z = 8. The asymmetric unit of compound 5 consists of two independent molecules 5I and 5II. Both molecules exhibit the disorder of each methylene group present in their 1,4-dioxane rings with relative occupancies of 0.599(10) (5I) and 0.812(9) (5II) for the major component A, and 0.401(10) (5I) and 0.188(9) (5II) for the minor component B, respectively. Each independent molecule revealed remarkable discrepancies in bond lengths, bond angles and dihedral angles in the disordered regions of 1,4-dioxane rings. The common feature of the molecules 5I and 5II are a chromone ring and a benzodioxin ring, which are more tilted towards each other in 5I than in 5II. An additional difference between the molecules is seen in the relative disposition of two methoxy substituents. In the crystal, the molecule 5II forms inversion dimers which are linked into chains along an a-axis direction by intermolecular C–H⋯O interactions. Additional C–H⋯O hydrogen bonds connected the molecules 5I and 5II each other to form a three-dimensional network. Hirshfeld surface analysis evaluated the relative intermolecular interactions which contribute to each crystal structure 5I and 5II. Western blot analysis demonstrated that compound 5 inhibited the TNFα-induced phosphorylation of IKKα/β, resulting in attenuating further downstream NF-κB signaling. A molecular docking study predicted the possible binding of compound 5 to the active site of IKKβ. Compound 5 showed an inhibitory effect on the clonogenicity of HCT116 human colon cancer cells. These results suggest that compound 5 can be used as a platform for the development of an anti-cancer agent targeting IKKα/β.

Synthesis of some new functionalized pyrano[2,3-c]pyrazoles and pyrazolo[4′,3′:5,6] pyrano[2,3-d]pyrimidines bearing a chromone ring as antioxidant agents

A new series of functionalized pyrano[2,3-c]pyrazoles and pyrazolo[4′,3′:5,6]pyrano [2,3-d]pyrimidines bearing a bioactive chromone ring was achieved. The methodology depended on treatment of 6-amino-4-(4-oxo-4H-chromen-3-yl)-3-phenyl-1,4-dihydropyrano [2,3-c]pyrazole-5-carbonitrile (3) with different electrophilic reagents. All the synthesized compounds were fully characterized by spectroscopic data and screened for their in vitro antioxidant activity using DPPH radical scavenging methods. A preliminary study of the structure–activity relationship revealed that the combination of pyranopyrazole skeleton with pyrimidine moiety along with NH and OH groups enhanced overall the antioxidant properties.

Further Quantitative Structure-Cytotoxicity Relationship Analysis of 3-Styrylchromones.

Very few studies are available about the biological activity of 3-styrylchromones. Our previous study demonstrated the importance of methoxy group at 6-position of the chromone ring and hydroxyl group at 4'-position of phenyl group in styryl moiety. As a sequel of this study, we synthesized fourteen compounds that include eight 3-styrylchromones where methoxy group was introduced at 7-position of chromone rings, and then evaluated their tumor-specificity. Tumor-specificity (TS) was calculated by relative cytotoxicity against human oral squamous cell carcinoma cell lines versus human normal oral cells. Apoptosis induction and growth arrest were monitored by cell-cycle analysis. Quantitative structure-activity relationship analysis of TS was performed with 3,167 chemical descriptors. Two compounds, 7-methoxy-3-[(1E)-2-phenylethenyl]-4H-1-benzopyran-4-one [7] and 3-[(1E)-2-(4-hydroxyphenyl)ethenyl]-7-methoxy-4H-1-benzopyran-4-one [14] showed higher tumor-specificity than doxorubicin and 5-FU, suggesting the importance of methoxy group in 7-position of the chromone ring. These compounds induced the apoptosis and mitotic arrest in HSC-2 cells. The tumor-specificity of 3-styrylchromone derivatives were most correlated with descriptors for molecule shape and electronic charge. The present study suggested that modification by introducing methoxy group at 7-position, instead at 6-position, further increased the tumor-specificity of 3-styrylchromone.