Antitumoral activity of quinoxaline derivatives: A systematic review

Iron-Catalyzed C-H Arylphosphorylation of Quinoxalines

A one-pot strategy for iron-catalyzed C2,3-H arylphosphorylation of electron-deficient quinoxalines with phosphines and aryl compounds is reported. The proposed method features the use of non-noble metal catalysts, the capacity of utilizing multiple aryl compounds as substrates, the simultaneous formation of C-P and C-C bonds in one pot, the simplicity of its operation, the mildness of the reaction conditions, and its compatibility with a wide range of substrates. Moreover, it offers a practical route for direct access to 2-aryl-3-phosphino N-heteroarenes, a class of potential cyclometalated C^N and N^P bidentate ligands that are difficult to prepare with existing C(sp2)-H functionalization methods.

Synthesis of quinoxalines and assessment of their inhibitory effects against human non-small-cell lung cancer cells

Twenty-six quinoxalin derivatives were synthesized to assess their biological activities against human non-small-cell lung cancer cells (A549 cells). Compound 4b (IC50 = 11.98 ± 2.59 μM) and compound 4m (IC50 = 9.32 ± 1.56 μM) possess anticancer activity comparable to 5-fluorouracil (clinical anticancer drug) (IC50 = 4.89 ± 0.20 μM). Western blot tests further confirmed that compound 4m effectively induced apoptosis of A549 cells through mitochondrial- and caspase-3-dependent pathways. The introduction of bromo groups instead of nitro groups into the quinoxaline skeleton has been shown to provide better inhibition against lung cancer cells in this article. This modification in the molecular structure could enhance the biological activity and effectiveness of quinoxaline derivatives in the design and synthesis of anticancer drugs, making bromo-substituted quinoxalines a promising avenue for further research and development in anticancer therapeutics.

Recent advances on quinoxalines as target-oriented chemotherapeutic anticancer agents through apoptosis

The current review outlines all possible recent synthetic platforms to quinoxaline derivatives and the potent stimulated apoptosis mechanisms targeted by anticancer therapies. The currently reported results disclosed that quinoxaline derivatives had promising anticancer potencies against a wide array of cancer cell lines, better than the reference drugs, through target inhibition. This review summarizes some potent quinoxaline derivatives with their synthesis strategies and their potential activities against various molecular targets. Quinoxalines can be considered an important scaffold for apoptosis inducers in cancer cells through inhibiting some molecular targets, so they can be further developed as target-oriented chemotherapeutics.

A novel green and efficient heterogeneous acid catalyst for the one-pot synthesis of benzopyrazine-aminoimidazole hybrids with antiproliferative potential

A novel, green, efficient, and stable magnetically heterogeneous nanocatalyst was developed by immobilizing butanesulfonic acid (BuSO3H) onto the surface of MFe2O4 magnetic nanoparticles (MNPs). The resulting core-shell structure of the MFe2O4@PDA@BuSO3H nanocatalyst was thoroughly characterized using various analytical techniques, including Fourier-Transform Infrared Spectroscopy (FT-IR), X-ray Diffraction (XRD), Energy-Dispersive X-ray Spectroscopy (EDS), Field Emission Scanning Electron Microscopy (FESEM), Transmission Electron Microscopy (TEM), Vibrating Sample Magnetometry (VSM), and Brunauer-Emmett-Teller (BET) analysis. A nanocatalyst was used to synthesize 2-benzopyrazine-aminoimidazole hybrid derivatives through a domino multicomponent Knoevenagel-condensation-cyclization reaction (5a-p) in an environmentally friendly manner. The resulting compounds were then tested for their anticancer activity against three types of human cancer cells (MCF-7, A549, and U87) using the MTT assay. The experiment showed that the nanocatalyst had excellent catalytic activity, and the synthesized compounds exhibited promising antiproliferative activity. Notably, compounds 5g and 5h, containing a 2-naphthyl ring, showed the highest antiproliferative effects against MCF-7 cells, with IC50 values of 0.03 and 0.32 μM, respectively. Additionally, the activity of compounds 5g and 5h in tubulin polymerization, apoptosis induction, and cell cycle arrest in MCF-7 cells were investigated. The results demonstrated that these compounds effectively induced apoptosis and cell cycle arrest. The binding of representative compounds to the colchicine binding site of tubulin was confirmed through molecular modeling studies.

Anticancer, anti-inflammatory and analgesic activities of aminoalcohol-based quinoxaline small molecules

PURPOSE

Bioactive molecules are relevant to fight cancer and associated conditions. Quinoxaline is a privileged N-heterocycle, notably as anticancer agents. Herein, we report the evaluation of the quinoxaline derivatives DEQX and OAQX as anticancer agents, as well as in function of their anti-inflammatory and analgesic activities.

METHODS

Quinoxalines were synthesized and tested as anticancer agents based on cell viability and Annexin V-FITC apoptosis. Anti-inflammatory activity was evaluated from mouse carrageenan peritonitis and levels of interleukin (IL)-1β and tumor necrosis factor (TNF)-alfa for enzyme-linked immunosorbent assay. Hot-plate and acetic acid-induced writing test were employed to investigate analgesia.

RESULTS

Both reduced the Ht-29 cell viability in a dependent-concentration manner (p < 0.001). Total apoptosis was detected for cells treated with 12.5 and 25 µg/mL of both the compounds for 24 and 48 h (all doses, p < 0.0001). DEQX (all doses, p < 0.01) and OAQX (all doses, p < 0.001) acted in leukocyte migration and decreased the IL-1β and TNF-β levels (p < 0.05). DEQX (all doses, p < 0.05) and OAQX (5mg/kg, p < 0.001) showed peripheral analgesic effect.

CONCLUSIONS

In-vitro and in-vivo results suggest that these quinoxalines are promising for application in pharmacological area due to their anticancer, anti-inflammatory, and peripheric analgesia.

Inhibition of protein misfolding and aggregation by steroidal quinoxalin-2(1H)-one and their molecular docking studies

A series of D-ring fused 16-substituted steroidal quinoxalin-2(1H)-one attached to an electron-releasing (ER) or electron-withdrawing (EW) groups via steroidal oxoacetate intermediate were synthesized to investigate their protein aggregation inhibition potential using human lysozyme (HLZ). The influence of the type of substituent at the C-6 positions of the quinoxalin-2(1H)-one ring on the protein aggregation inhibition potential was observed, showing that the EW moiety improved the protein aggregation inhibition potency. Of all the evaluated compounds, NO2-substituted quinoxalin-2(1H)-one derivative 13 was the most active compound and had a maximum protein aggregation inhibition effect. Significant stabilization effects strongly support the binding of the most biologically active steroidal quinoxalin-2(1H)-one with docking studies. The predicted physicochemical and ADME properties lie within a drug-like space which shows no violation of Lipinski's rule of five except compounds 12 and 13. Combined, our results suggest that D-ring fused 16-substituted steroidal quinoxalin-2(1H)-one has the potential to modulate the protein aggregation inhibition effect.

Design, Synthesis, Antifungal Activity, and 3D-QSAR Study of Novel Quinoxaline-2-Oxyacetate Hydrazide

Plant pathogenic fungi pose a major threat to global food security, ecosystem services, and human livelihoods. Effective and broad-spectrum fungicides are needed to combat these pathogens. In this study, a novel antifungal 2-oxyacetate hydrazide quinoxaline scaffold as a simple analogue was designed and synthesized. Their antifungal activities were evaluated against Botrytis cinerea (B. cinerea), Altemaria solani (A. solani), Gibberella zeae (G. zeae), Rhizoctonia solani (R. solani), Colletotrichum orbiculare (C. orbiculare), and Alternaria alternata (A. alternata). These results demonstrated that most compounds exhibited remarkable inhibitory activities and possessed better efficacy than ridylbacterin, such as compound 15 (EC50 = 0.87 μg/mL against G. zeae, EC50 = 1.01 μg/mL against C. orbiculare) and compound 1 (EC50 = 1.54 μg/mL against A. alternata, EC50 = 0.20 μg/mL against R. solani). The 3D-QSAR analysis of quinoxaline-2-oxyacetate hydrazide derivatives has provided new insights into the design and optimization of novel antifungal drug molecules based on quinoxaline.

Quinoxaline derivatives: Recent discoveries and development strategies towards anticancer agents

Cancer is a leading cause of death and a major health problem worldwide. While many effective anticancer agents are available, most drugs currently on the market are not specific, raising issues like the common side effects of chemotherapy. However, recent research hold promises for the development of more efficient and safer anticancer drugs. Quinoxaline and its derivatives are becoming recognized as a novel class of chemotherapeutic agents with activity against different tumors. The present review compiles and discusses studies concerning the therapeutic potential of the anticancer activity of quinoxaline derivatives, covering articles published between January 2018 and January 2023.

Exploring theophylline-1,2,4-triazole tethered N-phenylacetamide derivatives as antimicrobial agents: unraveling mechanisms via structure-activity relationship, in vitro validation, and in silico insights

Theophylline, a nitrogen-containing heterocycle, serves as a promising focal point for medicinal researchers aiming to create derivatives with diverse pharmacological applications. In this work, we present an improved synthetic method for a range of theophylline-1,2,4-triazole-S-linked N-phenyl acetamides (4a‒g) utilizing ultrasound-assisted synthetic approach. The objective was to assess the effectiveness of synthesized theophylline-1,2,4-triazoles (4a‒g) as inhibitors of HCV serine protease and as antibacterial agents against B. subtilis QB-928 and E. coli AB-274. Theophylline-1,2,4-triazoles were obtained in good to excellent yields (69%-95%) in a shorter time than conventional approach. 4-Chlorophenyl moiety containing theophylline-1,2,4-triazole 4c displayed significantly higher inhibitory activity against HCV serine protease enzyme (IC50 = 0.015 ± 0.25 mg) in comparison to ribavirin (IC50 = 0.165 ± 0.053 mg), but showed excellent binding affinity (-7.55 kcal/mol) with the active site of serine protease, better than compound 4c (-6.90 kcal/mol) as well as indole-based control compound 5 (-7.42 kcal/mol). In terms of percentage inhibition of serine protease, 2-chlorophenyl compound 4b showed the maximum percentage inhibition (86%), more than that of the 3,4-dichlorophenyl compound 4c (76%) and ribavirin (81%). 3,4-Dimethylphenyl-based theophylline-1,2,4-triazole 4g showed the lowest minimum inhibitory concentration (MIC = 0.28 ± 0.50 μg/mL) against the B. subtilis bacterial strain as compared to the standard drug penicillin (MIC = 1 ± 1.50 μg/mL). The other 4-methylphenyl theophylline-1,2,4-triazole 4e (MIC = 0.20 ± 0.08 μg/mL) displayed the most potent antibacterial potential against E. coli in comparison to the standard drug penicillin (MIC = 2.4 ± 1.00 μg/mL). Molecular docking studies further helped in an extensive understanding of all of the interactions between compounds and the enzyme active site, and DFT studies were also employed to gain insights into the molecular structure of the synthesized compounds. The results indicated that theophylline-linked triazole derivatives 4b and 4c showed promise as leading contenders in the fight against the HCV virus. Moreover, compounds 4e and 4g demonstrated potential as effective chemotherapeutic agents against E. coli and B. subtilis, respectively. To substantiate these findings, additional in vivo studies and clinical trials are imperative, laying the groundwork for their integration into future drug design and development.

Synthesis, Spectral Characterization and Photoluminescence of 3-chloro-6-methoxy-2-(methylsulfanyl)quinoxaline in Different Solvents: An Experimental and Theoretical Investigation Using DFT

In the present work, we synthesized 3-chloro-6-methoxy-2-(methyl sulfanyl) quinoxaline (3MSQ) using a microwave-assisted synthesis method. The physicochemical structural analysis of the synthesized compound utilizing 1H-NMR, 13C-NMR, and FT-IR spectroscopy techniques. The photophysical properties of 3MSQ was examined through absorption and fluorescence spectroscopy. Spectroscopic analyses revealed a bathochromic shift in both absorption and fluorescence spectra, attributed to the π → π* transition. Ground and excited state dipole moments was experimentally determined using the solvatochromic shift method, employing various correlations such as Lippert's, Bakhshiev's, Kawski-Chamma-Viallet's equations, and solvent polarity parameters. Our findings indicate that the excited state dipole moments exceed those of the ground state, suggesting increased polarity in the excited state. Further, the while detailed bond length, bond angles, dihedral angles, Mulliken charge distribution, ground state dipole moments and HOMO-LUMO energy gap estimated through ab initio computations using Gaussian-09W. The value of energy band gap obtained from both the methods are in good agreement. Furthermore, employing DFT computational analysis, we identified reactive centers such as electrophilic and nucleophilic sites using molecular electrostatic potential (MESP) 3D plots. Additionally, CIE chromaticity analysis was performed to understand the photoluminescent properties of 3MSQ. The insights derived from these analyses contribute to a better understanding of the molecule's electronic structure, photophysical properties, and solute-solvent interactions, thus providing valuable information regarding its behaviour and characteristics under diverse conditions. These results contribute to a comprehensive understanding of the molecular structure and properties of 3-chloro-6-methoxy-2-(methyl sulfanyl) quinoxaline (3MSQ).

Manganese-catalyzed Efficient Synthesis of N-heterocycles and Aminoketones Using Glycerol as a C3 Synthon

Glycerol is one of the important biomass-derived feedstocks and the high-value utilizations of glycerol have attracted much attentions in recent years. Herein, we report a manganese catalyzed dehydrogenative coupling of glycerol with amines for the synthesis of substituted 2-methylquinoxalines, 2-ethylbenzimidazoles, and α-aminoketones without any external oxidant. In these reactions, NHC-based pincer manganese complex featuring a pyridine backbone displayed high catalytic activity and selectivity, in which hydrogen and water were produced as the only by-products using glycerol as a C3 synthon.

Design, synthesis, and biological evaluation of novel quinoxaline aryl ethers as anticancer agents

We designed and synthesized thirty novel quinoxaline aryl ethers as anticancer agents, and the structures of final compounds were confirmed with various analytical techniques like Mass, 1 H NMR, 13 C NMR, FTIR, and elemental analyses. The compounds were tested against three cancer cell lines: colon cancer (HCT-116), breast cancer (MDA-MB-231), prostate cancer (DU-145), and one normal cell line: human embryonic kidney cell line (HEK-293). The obtained results indicate that two compounds, FQ and MQ, with IC50 values < 16 μM, were the most active compounds. Molecular docking studies revealed the binding of FQ and MQ molecules in the active site of the c-Met kinase (PDB ID: 3F66, 1.40 Å). Furthermore, QikProp ADME prediction and the MDS analysis preserved those critical docking data of both compounds, FQ and MQ. Western blotting was used to confirm the impact of the compounds FQ and MQ on the inhibition of the c-Met kinase receptor. The apoptosis assays were performed to investigate the mechanism of cell death for the most active compounds, FQ and MQ. The Annexin V/7-AAD assay indicated apoptosis in MDA-MB-231 cells treated with FQ and MQ, with FQ (21.4%) showing a higher efficacy in killing MDA-MB-231 cells than MQ (14.25%). The Caspase 3/7 7-AAD assay further supported these findings, revealing higher percentages of apoptotic cells for FQ-treated MDA-MB-231 cells (41.8%). The results obtained from the apoptosis assay conclude that FQ exhibits better anticancer activity against MDA-MB-231 cells than MQ.

Design, synthesis, in silico molecular docking, and ADMET studies of quinoxaline-isoxazole-piperazine conjugates as EGFR-targeting agents

In this paper, we report the synthesis of quinoxaline-isoxazole-piperazine conjugates. The anticancer activity was evaluated against three human cancer cell lines, including MCF-7 (breast), HepG-2 (liver), and HCT-116 (colorectal). The outcomes of the tested compounds 5d, 5e, and 5f have shown more potent activity when compared to the standard drug erlotinib. In a cell survivability test (MCF-10A), three potent compounds (5d, 5e, and 5f) were evaluated against the normal breast cell line, although neither of them displayed any significant cytotoxicity with IC50 values greater than 84 μM. Furthermore, the compounds 5d, 5e, and 5f were tested for tyrosine kinase EGFR inhibitory action using erlotinib as the reference drug and compound 5e was shown to be more potent in inhibiting the tyrosine kinase EGFR than sorafenib. In addition to this, molecular docking studies of compounds 5d, 5e, and 5f demonstrated that these compounds had more EGFR-binding interactions. The potent compounds 5d, 5e, and 5f were subjected to in silico pharmacokinetic assessment by SWISS, ADME, and pkCSM. While the compounds 5d, 5e, and 5f followed Lipinski, Veber, Egan, and Muegge rules without any deviation.

AlCl3-Promoted Intramolecular Indolinone-Quinolone Rearrangement of Spiro[indoline-3,2'-quinoxaline]-2,3'-diones: Easy Access to Quinolino[3,4-b]quinoxalin-6-ones

A facile and direct intramolecular indolinone-quinolone rearrangement was developed for the synthesis of quinolino[3,4-b]quinoxalin-6-ones from spiro[indoline-3,2'-quinoxaline]-2,3'-diones, which are readily available with use of isatines, malononitrile, and 1,2-phenylenediamines under quite mild conditions. This efficient approach provides excellent yields and could potentially be used for the construction of a diverse library of quinolino[3,4-b]quinoxalin-6-ones for high-throughput screening in medicinal chemistry. The reaction mechanism is explored by extensive DFT calculations.

A new triazolyl-indolo-quinoxaline induces apoptosis in gastric cancer cells by abrogating the STAT3/5 pathway through upregulation of PTPεC

Signal transducer and activator of transcription 3 (STAT3) and STAT5 are the transcription factors that have been studied extensively in relevance to the development of cancers in humans. Suppression of either STAT3 or STAT5-mediated signaling events has been demonstrated to be effective in inducing cytotoxicity in cancer cells. Herein, new hybrids of triazolyl-indolo-quinoxaline are synthesized and examined for their effect on the activation of STAT3 and STAT5 pathways in gastric cancer (GC) cells. Among the newly synthesized compounds, 2,3-difluoro-6-((1-(3-fluorophenyl)-1H-1,2,3-triazol-5-yl)methyl)-6H-indolo[2,3-b]quinoxaline (DTI) displayed selective cytotoxicity against GC cells over their normal counterpart. Flow cytometric analysis, annexin-V-fluorescein isothiocyanate staining, terminal deoxynucleotidyl transferase dUTP nick end labeling assay, live and dead assay, and caspase activation experiments suggested DTI as a potent inducer of apoptosis. The mechanistic approach revealed that DTI imparts cytotoxicity via downregulating the phosphorylation of STAT3Y705 and STAT5Y694/699 . DTI significantly reduced the nuclear pool of STAT3/STAT5 and reduced the DNA interaction ability of STAT3/STAT5 as evidenced by immunofluorescence and electrophoretic mobility shift assay. Further investigation revealed that inhibitory effects towards STAT proteins were mediated through the suppression of upstream kinases such as JAK1, JAK2, and Src. Treatment of GC cells with pervanadate counteracted the DTI-driven STAT3/STAT5 inhibition suggesting the involvement of tyrosine phosphatase. Upon DTI exposure, there was a significant upregulation in the mRNA and protein expression of PTPεC, which is a negative regulator of the JAK-STAT pathway. Knockdown of PTPεC suppressed the DTI-induced STATs inhibition in GC cells. Taken together, triazolyl-indolo-quinoxaline is presented as a new inhibitor of the STAT3/STAT5 pathway in GC cells.

A multispectroscopic approach for ultra-trace sensing of prostate specific antigen (PSA) by iron nanocomposite fabricated on graphene nanoplatelet

Herein we report an easy, rapid and cost-effective method for spectroscopic sensing of a prostate cancer biomarker prostate specific antigen (PSA) using a novel nanocomposite. The material is a synthetic quinoxaline derivative-based iron nanocomposite fabricated on graphene nanoplatelet surface (1d-Fe-Gr). Presence of graphene enhanced the efficacy of synthesized 1d-Fe-Gr to sense PSA in serum medium with an impressive limit of detection (LOD) value of 0.878 pg/mL compared to 1d-Fe alone (LOD 17.619 pg/mL) using UV-visible absorption spectroscopy. LOD of PSA by 1d-Fe-Gr using Raman spectroscopy is even more impressive (0.410 pg/mL). Moreover, presence of interfering biomolecules like glucose, cholesterol, bilirubin and insulin in serum improves the detection threshold significantly in presence of 1d-Fe-Gr which otherwise cause LOD values of PSA to elevate in control sets. In presence of these biomolecules, the LOD values improve significantly as compared to healthy conditions in the range 0.623-3.499 pg/mL. Thus, this proposed detection method could also be applied efficiently to the patients suffering from different pathophysiological disorders. These biomolecules may also be added externally during analyses to improve the sensing ability. Fluorescence, Raman and circular dichroism spectroscopy were used to study the underlying mechanism of PSA sensing by 1d-Fe-Gr. Molecular docking studies confirm the selective interaction of 1d-Fe-Gr with PSA over other cancer biomarkers.

Novel quinoxaline-3-propanamides as VGFR-2 inhibitors and apoptosis inducers

Vascular endothelial growth factor receptor-2 is a vital target for therapeutic mediation in various types of cancer. This study was aimed at exploring the cytotoxic activity of seventeen novel quinoxaline-3-propanamides against colon cancer (HCT-116) and breast cancer (MCF-7) using MTT assay. Results revealed that compounds 8, 9, and 14 elicited higher cytotoxicity than the reference drugs, doxorubicin (DOX) and sorafenib. Interestingly, they are more selective for HCT-116 (SI 11.98-19.97) and MCF-7 (SI 12.44-23.87) compared to DOX (SI HCT-116 0.72 and MCF-7 0.9). These compounds effectively reduced vascular endothelial growth factor receptor-2; among them, compound 14 displayed similar VEGFR-2 inhibitory activity to sorafenib (IC50 0.076 M). The ability of 14 to inhibit angiogenesis was demonstrated by a reduction in VEGF-A level compared to control. Furthermore, it induced a significant increase in the percentage of cells at pre-G1 phase by almost 1.38 folds (which could be indicative of apoptosis) and an increase in G2/M by 3.59 folds compared to the control experiment. A flow cytometry assay revealed that compound 14 triggered apoptosis via the programmed cell death and necrotic pathways. Besides, it caused a remarkable increase in apoptotic markers, i.e., caspase-3 p53 and BAX. When compared to the control, significant increase in the expression levels of caspase-3 from 47.88 to 423.10 and p53 from 22.19 to 345.83 pg per ml in MCF-7 cells. As well, it increased the proapoptotic protein BAX by 4.3 times while lowering the antiapoptotic marker BCL2 by 0.45 fold. Docking studies further supported the mechanism, where compound 14 showed good binding to the essential amino acids in the active site of VEGFR-2. Pharmacokinetic properties showed the privilege of these hits over sunitinib: they are not substrates of P-gp protein; this suggests that they have less chance to efflux out of the cell, committing maximum effect; and in addition, they do not allow permeation to the BBB.

Design, synthesis, and docking studies of novel pyrazole-based scaffolds and their evaluation as VEGFR2 inhibitors in the treatment of prostate cancer

Since VEGFR-2 plays a crucial role in tumor growth, angiogenesis, and metastasis, it is a prospective target for cancer treatment. In this work, a series of 3-phenyl-4-(2-substituted phenylhydrazono)-1H-pyrazol-5(4H)-ones (3a-l) were synthesized and investigated for their cytotoxicity against the PC-3 human cancer cell line compared to Doxorubicin and Sorafenib as reference drugs. Two compounds 3a and 3i showed comparable cytotoxic activity with IC₅₀ values of 1.22 and 1.24 μM compared to the reference drugs (IC₅₀ = 0.932, 1.13 μM). Compound 3i was found to be the most effective VEGFR-2 inhibitor using in vitro testing of the synthesized compounds, with nearly 3-fold higher activity than Sorafenib (30 nM), with IC₅₀ 8.93 nM. Compound 3i significantly stimulated total apoptotic prostate cancer cell death 55.2-fold (34.26% compared to 0.62% for the control) arresting the cell cycle at the S-phase. The genes involved in apoptosis were also impacted, with proapoptotic genes being upregulated and antiapoptotic Bcl-2 being downregulated. These results were supported by docking studies of these two compounds within the active site of the VEGFR2 enzyme. Finally, in vivo, the study revealed the potentiality of compound 3i to inhibit tumor proliferation by 49.8% reducing the tumor weight from 234.6 mg in untreated mice to 83.2 mg. Therefore, 3i could be a promising anti-prostate cancer agent.

Reusable nano-catalyzed green protocols for the synthesis of quinoxalines: an overview

Heterocyclic compounds are very widely distributed in nature and are essential for life activities. They play a vital role in the metabolism of all living cells, for example, vitamins and co-enzyme precursors thiamine, riboflavin etc. Quinoxalines are a class of N-heterocycles that are present in a variety of natural and synthetic compounds. The distinct pharmacological activities of quinoxalines have attracted medicinal chemists considerably over the past few decades. Quinoxaline-based compounds possess extensive potential applications as medicinal drugs, presently; more than fifteen drugs are available for the treatment of different diseases. Diverse synthetic protocols have been developed via a one-pot approach using efficient catalysts, reagents, and nano-composites/nanocatalysts etc. But the use of homogeneous and transition metal-based catalysts suffers some demerits such as low atom economy, recovery of catalysts, harsh reaction conditions, extended reaction period, expensive catalysts, the formation of by-products, and unsatisfactory yield of products as well as toxic solvents. These drawbacks have shifted the attention of chemists/researchers to develop green and efficient protocols for synthesizing quinoxaline derivatives. In this context, many efficient methods have been developed for the synthesis of quinoxalines using nanocatalysts or nanostructures. In this review, we have summarized the recent progress (till 2023) in the nano-catalyzed synthesis of quinoxalines using condensation of o-phenylenediamine with diketone/other reagents with plausible mechanistic details. With this review, we hope that some more efficient ways of synthesizing quinoxalines can be developed by synthetic chemists.

Synthesis, molecular docking and dynamics studies of pyridazino[4,5-b]quinoxalin-1(2H)-ones as targeting main protease of COVID-19

The COVID-19 pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has created a crisis in public health. Because, the 3CLpro, the main protease of SARS-CoV-2, possesses a critical role in coronavirus replication, many efforts have been devoted to developing various inhibitors to prevent the fast spread of COVID-19. In the current work, a number of various pyridazino[4,5-b]quinoxalin-1(2H)-one derivatives bearing thiadiazine and thiadiazole fragments has been prepared via a straightforward and practical strategy involving the reaction of 2-(ethoxycarbonyl)-3-formylquinoxaline 1,4-dioxide with thiocarbohydrazide under reflux conditions. To determine the bioavailability of pyridazino[4,5-b]quinoxalin-1(2H)-one derivatives, Lipinski's rule of five has been carried out. Regarding this rule, none of the synthesized compounds exhibit any deviation from Lipinski's rule of five. Furthermore, molecular docking and molecular dynamics approaches have been implemented to figure out the potential interactions of products with SARS-CoV-2 main protease. The outcomes of molecular docking studies demonstrate that the phenyl and nitrophenyl substituted pyridazino[4,5-b]quinoxalin-1(2H)-one show the lowest binding affinity among the other compounds, indicating a favorable orientation in the active site of the chymotrypsin-like cysteine protease. In addition, the MD simulation performed to evaluate the stability of the protein-ligand complex represents that the average binding energy of the nitrophenyl complex is less than that of the phenyl complex. Therefore, according to the in silico results, the inhibitory effect of the nitrophenyl complex is more significant than the phenyl complex.Communicated by Ramaswamy H. Sarma.

Novel imino-thiazoloquinoxaline derivatives against renal cell carcinoma: less radiation-damaging approach

Renal cell carcinoma (RCC) is the most fatal tumor in the urinary system. Resistance development and unmet effective responses, request new anticancer agents with better therapeutic index. Ten new imino-thiazolo-quinoxaline derivatives (5a-j) were synthesized and preliminary evaluated for downregulation of Vascular Endothelial Growth Factor Receptor-2 (VEGFR-2) activity taking sorafenib as a reference drug. Compounds 5d & 5h showed potent inhibition to VEGFR-2 activity at IC50 89.35 nM & 60.64 nM, respectively, then they both were further evaluated in-vitro against urinary bladder cancer cell line T-24 taking sorafenib as a reference drug. Compound 5h displayed nearly anticancer activity to sorafenib against T-24 cell line in all concentrations tested except at concentration 10 µM where it highly suppressed cell viability to 6.71 % compared to 15.15% of sorafenib. Compound 5h was then evaluated for its ameliorative efect against radiation induced renal tissue injury. Assessment of pro-angiogenic (VEGFR-2), pro-fibrotic (transforming growth factor-beta 1 (TGF-β1)) and apoptotic (caspase-3) markers, as well as histopathological examinations were performed on kidney of irradiated mice. Results showed ability of compound 5h to downregulate VEGFR-2 activity and its cytotoxic effect against RCC, in addition to mitigation of radiation induced renal tissue injury. Ethyl imino-thiazoloquinoxaline carboxylate derivative 5h showed a potential cytotoxic activity against RCC and could be considered a promosing alleviative candidate when employed post radiotherapy regimen.

Graphical Abstract

Water-soluble extracellular vesicle probes based on conjugated oligoelectrolytes

We developed a series of transmembrane conjugated oligoelectrolytes (COEs) with tunable optical emissions from the UV to the near IR to address the false-positive problem when detecting nanometer-sized extracellular vesicles (EVs) by flow cytometry. The amphiphilic molecular framework of COEs is defined by a linear conjugated structure and cationic charged groups at each terminal site. Consequently, COEs have excellent water solubility and the absence of nanoaggregates at concentrations up to 50 μM, and unbound COE dyes can be readily removed through ultrafiltration. These properties enable unambiguous and simple detection of COE-labeled small EVs using flow cytometry with negligible background signals. We also demonstrated the time-lapsed tracking of small EV uptake into mammalian cells and the endogenous small EV labeling using COEs. Briefly, COEs provide a class of membrane-targeting dyes that behave as biomimetics of the lipid bilayer and a general and practical labeling strategy for nanosized EVs.

Synthesis of D-π-A'-π-A Chromophores with Quinoxaline Core as Auxiliary Acceptor and Effect of Various Silicon-Substituted Donor Moieties on Thermal and Nonlinear Optical Properties at Molecular and Material Level

Novel D-π-A'-π-A chromophores with quinoxaline cores as auxiliary acceptors and various donor moieties (aniline, carbazole, phenothiazine, tetrahydroquinoline) containing bulky tert-butyldimethylsilyloxy (TBDMSO) groups and tricyanofuranyl (TCF) acceptors with bulky cyclohexylphenyl substituents were synthesized via eight- to nine-step procedures, and their photo-physical and thermal properties were investigated. The values of the chromophores' first hyperpolarizabilities were calculated in the framework of DFT at the M06-2X/aug-cc-pVDZ computational level; the effect of the introduction of the TBDMSO group into the donor fragment is shown to be inessential, as this group is not coupled to the π-conjugated system of the chromophore. The chromophore with the tetrahydroquinoline donor has a first hyperpolarizability value of 937 × 10^-30 esu, which is the highest for the studied chromophores. Atomistic modeling of composite materials with the studied chromophores as guests demonstrated that the presence of bulky substituent in the donor fragment prevents notable aggregation of chromophores, even at high chromophore content (40 wt.%). The nonlinear optical performance of guest-host materials with 25 and 40 wt.% of suggested chromophore content was studied using a second harmonic generation technique to give the NLO coefficient, d₃₃ up to 52 pm/V.

Discovery and SAR Study of Quinoxaline–Arylfuran Derivatives as a New Class of Antitumor Agents

A novel class of quinoxaline–arylfuran derivatives were designed, synthesized, and preliminarily evaluated for their antiproliferative activities in vitro against several cancer cell lines and normal cells. The representative derivative QW12 exerts a potent antiproliferative effect against HeLa cells (IC50 value of 10.58 μM), through inducing apoptosis and triggering ROS generation and the accumulation of HeLa cells in vitro. Western blot analysis showed that QW12 inhibits STAT3 phosphorylation (Y705) in a dose-dependent manner. The BLI experiment directly demonstrated that QW12 binds to the STAT3 recombination protein with a KD value of 67.3 μM. Furthermore, molecular docking investigation showed that QW12 specifically occupies the pY+1 and pY-X subpocket of the SH2 domain, thus blocking the whole transmission signaling process. In general, these findings indicated that the study of new quinoxaline–aryfuran derivatives as inhibitors of STAT3 may lead to new therapeutic medical applications for cancer in the future.

Successive Cleavage and Reconstruction of Lignin β-O-4 Models and Polymer to Access Quinoxalines

The construction of N-heterocyclic compounds from lignin remains a great challenge due to the complex lignin structure and the involvement of multiple steps, including the cleavage of lignin C-O linkages and the formation of heterocyclic aromatic rings. Herein, the first example of KOH mediated sustainable synthesis of quinoxaline derivatives from lignin β-O-4 model compounds in a one-pot fashion under transition-metal-free conditions has been achieved. Mechanistic studies suggested that this transformation includes highly coupled cascade steps of cleavage of C-O bonds, dehydrative condensation, sp³ C-H bond oxidative activation, and intramolecular dehydrative coupling reaction. With this protocol, a wide range of functionalized quinoxalines, including an important drug compound AG1295, were synthesized from lignin β-O-4 model compounds and β-O-4 polymer, showcasing the application potential of lignin in pharmaceutical synthesis.

Synthesis of Morpholine-, Piperidine-, and N-Substituted Piperazine-Coupled 2-(Benzimidazol-2-yl)-3-arylquinoxalines as Novel Potent Antitumor Agents

A novel series of 2-(benzimidazol-2-yl)quinoxalines with three types of pharmacophore groups, namely, piperazine, piperidine, and morpholine moieties, which are part of known antitumor drugs, was designed and synthesized. The compounds have been characterized by NMR and IR spectroscopy, high- and low-resolution mass spectrometry, and X-ray crystallography. 2-(Benzimidazol-2-yl)quinoxalines with N-methylpiperazine substituents showed promising activity against a wide range of cancer lines, without causing hemolysis and showing little cytotoxicity against normal human Wi-38 cells (human fetal lung). A mixture of regioisomers 2-(benzimidazol-2-yl)-3-(4-fluorophenyl)-6(and 7)-(4-methylpiperazin-1-yl)quinoxalines (mri BIQ 13da/14da) showed a highly selective cytotoxic effect against human lung adenocarcinoma (cell line A549) with a half-maximal inhibitory concentration at the level of doxorubicin with a selectivity index of 12. The data obtained by flow cytometry, fluorescence microscopy, and multiparametric fluorescence analysis suggested that the mechanism of the cytotoxic effect of the mri BIQ 13da/14da on A549 cells may be associated with the stopping of the cell cycle in phase S and inhibition of DNA synthesis as well as with the induction of mithochondrial apoptosis. Thus, mri BIQ 13da/14da can be considered as a leading compound deserving further study, optimization, and development as a new anticancer agent.

Transition-metal-catalyzed ortho C-H functionalization of 2-arylquinoxalines

Recently, direct C-H bond activation and functionalization has become a prodigious and hot topic among synthetic organic chemists due to its step-economic nature and substantial synthetic versatility. On the other hand, quinoxaline, a fused bicycle of benzene and pyrazine, has omnipresent applications in medicinal-, industrial- and materials chemistry. The presence of the N-1 atom in 2-arylquinoxaline enables chelation formation with a metal catalyst leading to the formation of ortho-substituted products. In this review, all articles related to the ortho C-H bond functionalization of 2-arylquinoxalines published up to May 2022 are highlighted.

A Convenient Way to Quinoxaline Derivatives through the Reaction of 2-(3-Oxoindolin-2-yl)-2-phenylacetonitriles with Benzene-1,2-diamines

Microwave-assisted reaction between 2-(3-oxoindolin-2-yl)-2-phenylacetonitriles andbenzene-1,2-diamines leads to the high-yielding formation of the corresponding quinoxalines as sole, easily isolaable products. The featured transformation involves unusual extrusion of phenylacetonitrile molecule and could be performed in a short sequence starting from commonly available indoles and nitroolefins.

Hydrazinyl thiazole linked indenoquinoxaline hybrids: Potential leads to treat hyperglycemia and oxidative stress; Multistep synthesis, α-amylase, α-glucosidase inhibitory and antioxidant activities

A library of hydrazinyl thiazole-linked indenoquinoxaline hybrids 1-36 were synthesized via a multistep reaction scheme. All synthesized compounds were characterized by various spectroscopic techniques including EI-MS (electron ionization mass spectrometry) and ¹H NMR (nuclear magnetic resonance spectroscopy). Compounds 1-36 were evaluated for their inhibitory potential against α-amylase, and α-glucosidase enzymes. Among thirty-six, compounds 2, 9, 10, 13, 15, 17, 21, 22, 31, and 36 showed excellent inhibition against α-amylase (IC₅₀ = 0.3-76.6 μM) and α-glucosidase (IC₅₀ = 1.1-92.2 μM). Results were compared to the standard acarbose (IC₅₀ = 13.5 ± 0.2 μM). All compounds were also evaluated for their DPPH (1,1-diphenyl-2-picrylhydrazyl) radical scavenging activity and compounds 2, 9, 10, 17, 21, 31, and 36 showed (SC₅₀ = 7.58-125.86 μM) as compared to the standard ascorbic acid (SC₅₀ = 21.50 ± 0.18 μM). Among this library, compounds 9 and 10 with a hydroxy group on the phenyl rings and thiosemicarbazide bearing intermediate 21 were identified as the most potent inhibitors against α-amylase, and α-glucosidase enzymes. The remaining compounds were found to be moderately active. The molecular docking studies were conducted to understand the binding mode of active inhibitors and kinetic studies of the active compounds followed competitive modes of inhibition.

Evaluation of synthetic 2-aryl quinoxaline derivatives as α-amylase, α-glucosidase, acetylcholinesterase, and butyrylcholinesterase inhibitors

Variety of 2-aryl quinoxaline derivatives 1-23 were synthesized in good yields, by reacting 1,2-phenylenediamine with varyingly substituted phenacyl bromides in the presence of pyridine catalyst. All molecules 1-23 were characterized by spectroscopic techniques and evaluated for their diverse biological potential against α-amylase (α-AMY), α-glucosidase (α-GLU), acetylcholinesterase (AChE), and butyrylcholinesterase (BChE) enzymes. Synthetic derivatives possess enhanced inhibitory potential against all enzymes at nanomolar concentrations. In particular, compound 14 was found much superior with IC₅₀ = 294.35, 198.21, 17.04, and 21.46 nM against α-AMY, α-GLU, AChE, and BChE, respectively, as compared to standard inhibitors. Furthermore, selected potent compounds, including 3, 4, 8, 14, 15, 17, and 18, were subjected to molecular docking studies to decipher the binding energies and interactions of ligands (synthetic molecules) with all four target enzymes.

Synthesis, In Vitro Antiproliferative Activity, and In Silico Evaluation of Novel Oxiranyl-Quinoxaline Derivatives

The quinoxaline core is a promising scaffold in medicinal chemistry. Multiple quinoxaline derivatives, such as the topoisomerase IIβ inhibitor XK-469 and the tissue transglutaminase 2 inhibitor GK-13, have been evaluated for their antiproliferative activity. Previous work reported that quinoxaline derivatives bearing an oxirane ring present antiproliferative properties against neuroblastoma cell lines SK-N-SH and IMR-32. Likewise, quinoxalines with an arylethynyl group displayed promising antineoplastic properties against glioblastoma and lung cancer cell lines, U87-MG and A549 respectively. Here, 40 new quinoxaline derivatives bearing an oxirane ring were synthesized using a tetrakis(dimethylamino)ethylene (TDAE) strategy and a Sonogashira cross-coupling reaction. Each reaction with TDAE furnished a pair of diastereoisomers cis and trans. These new compounds formed two series according to the substitution of position 2 on the quinoxaline core, with chlorine or phenylacetylene respectively. Each of these isomers was evaluated for antiproliferative activity against neuroblastoma cell lines SK-N-SH and IMR-32 by MTT assay. All cell viability assay results were analyzed using R programming, as well as a statistical comparison between groups of compounds. Our evaluation showed no difference in drug sensitivity between the two neuroblastoma cell lines. Moreover, trans derivatives were observed to display better activities than cis derivatives, leading us to conclude that stereochemistry plays an important role in the antiproliferative activity of these compounds. Further support for this hypothesis is provided by the lack of improvement in antineoplastic activity following the addition of the phenylacetylene moiety, probably due to steric hindrance. As a result, compounds with nitrofuran substituents from the TDAE series demonstrated the highest antiproliferative activity with IC₅₀ = 2.49 ± 1.33 μM and IC₅₀ = 3.96 ± 2.03 μM for compound 11a and IC₅₀ = 5.3 ± 2.12 μM and IC₅₀ = 7.12 ± 1.59 μM for compound 11b against SK-N-SH and IMR-32, respectively. Furthermore, an in silico study was carried out to evaluate the mechanism of action of our lead compounds and predict their pharmacokinetic properties.

Synthetic approach toward spiro quinoxaline-β-lactam based heterocyclic compounds: Spectral characterization, SAR, pharmacokinetic and biomolecular interaction studies

Series of spiro quinoxaline-β-lactam based heterocyclic compounds (QL 1 - QL 21) were synthesized and characterized by spectroscopic techniques like ¹H-NMR, LC-MS, FT-IR spectroscopy and elemental analysis. The binding mode and binding strength between compounds and calf thymus-DNA were estimated by UV-visible spectroscopy, viscosity measurement and molecular docking studies. The compounds bind with the DNA through partial intercalation mode. In the absorption titration experiment, the K_b values for all the synthesized compounds were found in the range of 0.24-0.64 × 10⁵ M^-1. The protein binding studies of all the synthesized compounds were evaluated by absorption titration experiment, and the K_b value for all the compounds was obtained in the range of 0.030-1.571 × 10⁴ M^-1. The compounds were screened against two Gram (+ve) and three Gram (-ve) bacteria for antimicrobial activity. The MIC values for all the synthesized compounds were found in 95-255 µM. The LC₅₀ values (cytotoxicity) of the synthesized compounds (QL 1-QL 21) were found in the range of 4.00-12.89 µg/mL. The ADME study was carried out using the online platform SwissADME and admetSAR to evaluate the pharmacokinetic profile of all the synthesized compounds. All the compounds were screened for anticancer activity against the human osteosarcoma (MG-63) cell line. The result shows that all the compounds exhibit effective anticancer activity.Communicated by Ramaswamy H. Sarma.

In vitro anticancer properties of anthocyanins: A systematic review

Anthocyanins have been associated with beneficial effects on human health. Cancer has been one of the main public health issues due to its aggressiveness and high mortality rate. This systematic review aimed to address recent research (from January 2000 to September 2021) on the anticancer activity of anthocyanins assessed by in vitro assays. The selected studies revealed that anthocyanins have anticancer potential by inhibiting cancer cell viability and proliferation, controlling cell cycle, and promoting apoptosis.

Synthesis, density functional theory calculation, molecular docking studies, and evaluation of novel 5-nitrothiophene derivatives for anticancer activity

Within the scope of this study, new 2-{2-[(5-nitrothiophen-2-yl)methylene]hydrazinyl}thiazole derivatives (2a-j) were synthesized and investigated for their potential anticancer and enzyme inhibition activities. Spectroscopic techniques were used to determine the structures of substances. The anticancer activities of compounds were detected in A549 human lung carcinoma and L929 murine fibroblast cell lines, determining cytotoxicity, apoptosis, mitochondrial membrane integrity, and caspase-3 activation. Compounds 2b bearing 4-nitrophenyl, 2c bearing phenyl, and 2d bearing 4-cyanophenyl moieties were specified with high anticancer activity, acting through an apoptotic pathway with an apoptosis ratio of 9.61%-15.59%. Mitochondrial membrane depolarization was determined to be 25.53% and 22.33% for compounds 2b and 2c, respectively. Furthermore, compound 2c exhibited excellent caspase-3 activation. A molecular docking study was realized with compound 2c on the caspase-3 enzyme. Furthermore, the electronic characteristics of the active compounds were investigated using density functional theory (DFT) at the B3LYP/6-31G (d, p) level. The frontier molecular orbital energy and atomic net charges were examined.

Ultrasound-assisted transition-metal-free catalysis: a sustainable route towards the synthesis of bioactive heterocycles

Heterocycles of synthetic and natural origin are a well-established class of compounds representing a broad range of organic molecules that constitute over 60% of drugs and agrochemicals in the market or research pipeline. Considering the vast abundance of these structural motifs, the development of chemical processes providing easy access to novel complex target molecules by introducing environmentally benign conditions with the main focus on improving the cost-effectiveness of the chemical transformation is highly demanding and challenging. Accordingly, sonochemistry appears to be an excellent alternative and a highly feasible environmentally benign energy input that has recently received considerable and steadily increasing interest in organic synthesis. However, the involvement of transition-metal-catalyst(s) in a chemical process often triggers an unintended impact on the greenness or sustainability of the transformation. Consequently, enormous efforts have been devoted to developing metal-free routes for assembling various heterocycles of medicinal interest, particularly under ultrasound irradiation. The present review article aims to demonstrate a brief overview of the current progress accomplished in the ultrasound-assisted synthesis of pharmaceutically relevant diverse heterocycles using transition-metal-free catalysis.

Synthesis of cinnamils and quinoxalines and their biological evaluation as anticancer agents

We synthesized multiple cinnamils and quinoxalines to evaluate their anticancer activity. Cinnamils were used as precursors for quinoxalines via condensation with 1,2-diaminobenzene. Among the 26 synthesized compounds reported in this article, we found that cinnamil 3l exhibited its inhibitory effect with an IC50 value of 1.45 ± 0.98 μM, significantly higher than doxorubicin (8.5 ± 0.85 μM) against pancreatic cancer cells (PANC-1). Additionally, cinnamil 3l (IC50 10.98 ± 3.63 μM) showed less cytotoxicity than doxorubicin to Hs68 cells (0.92 ± 1.11 μM). The colony formation assay demonstrated that 3l obviously decreased the PANC-1 cell viability, and Western blot assays confirmed that 3l markedly induced apoptosis of PANC-1 cells through Bax, Bcl-2, and caspase 3 signaling cascades. These results demonstrate that cinnamil 3l has great potential to be further developed as a promising chemotherapeutic agent for pancreatic cancer.

Indoles Oxidative Ring-Opening/Cyclization Cascade with the 1,2-Diaminoarenes: Direct Synthesis of 2-Aryl-3-(2-aminoaryl)quinoxalines

A mild oxidative sequential tandem reaction was developed to rapidly generate 2-aryl-3-(2-aminoaryl) quinoxalines. This method exploited 2-substituted indoles as substrate to form quinoxalines in a one-pot reaction. The key to this tandem reaction was the formation of 3-iodoindoles, which underwent Kornblum-type oxidation with DMSO to generate active imine 2-substitued 3H-indol-3-ones. The active imines were captured in situ by 1,2-diaminobenzenes to construct diverse quinoxalines. The transformation can be accomplished at room temperature with excellent functional group tolerance.