Interactions of Antiviral Indolo[2,3-b]quinoxaline Derivatives with DNA

PIFA-mediated intramolecular N-arylation of 2-aminoquinoxalines to afford indolo[2,3-b]quinoxaline derivatives

We present the PIFA-mediated intramolecular N-arylation of 2-aminoquinoxalines at room temperature for the first time. This method provides a wide range of indolo[2,3-b]quinoxalines in good to excellent yields within a short time. The C-H bond functionalization occurs without the need for an inert atmosphere or additives. Additionally, a double C-H bond functionalization was observed, where the first reaction forms a C-N bond (N-arylation) and the second forms a C-O bond, yielding an acetal-functionalized product. Mechanistic investigations suggest that the C-H bond functionalization proceeds through an ionic mechanism, whereas acetal functionalization follows a radical pathway. This method extends to the derivation of indoloquinoxalines, including the target compound BIQMCz.

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.

N-Heterocycles as Promising Antiviral Agents: A Comprehensive Overview

Viruses are a real threat to every organism at any stage of life leading to extensive infections and casualties. N-heterocycles can affect the viral life cycle at many points, including viral entrance into host cells, viral genome replication, and the production of novel viral species. Certain N-heterocycles can also stimulate the host's immune system, producing antiviral cytokines and chemokines that can stop the reproduction of viruses. This review focused on recent five- or six-membered synthetic N-heterocyclic molecules showing antiviral activity through SAR analyses. The review will assist in identifying robust scaffolds that might be utilized to create effective antiviral drugs with either no or few side effects.

Dual Antitubercular and Antileishmanial Profiles of Quinoxaline Di-N-Oxides Containing an Amino Acidic Side Chain

We present a new category of quinoxaline di-N-oxides (QdNOs) containing amino acid side chains with dual antituberculosis and antileishmanial activity. These compounds were synthesized by combining a regioselective 2,5-piperazinedione opening and a Beirut reaction and were screened for their activity against Mycobacterium tuberculosis and the promastigote and amastigote forms of representative species of the Leishmania genus. Most QdNOs exhibited promising antitubercular activity with IC50 values ranging from 4.28 to 49.95 μM, comparable to clinically established drugs. Structure-activity relationship analysis emphasized the importance of substituents on the aromatic ring and the side chain. Antileishmanial tests showed that some selected compounds exhibited activity comparable to the positive control miltefosine against promastigotes of Leishmania amazonensis and Leishmania donovani. Notably, some compounds were found to be also more potent and less toxic than miltefosine in intracellular amastigote assays against Leishmania amazonensis. The compound showing the best dual antitubercular and leishmanicidal profile and a good selectivity index, 4h, can be regarded as a hit compound that opens up new opportunities for the development of integrated therapies against co-infections.

Metal-free construction of dihydropyrazino[2,3-b]indoles from 2-aminoacetophenones, isocyanates and 1,2-diamines

A Brønsted acid/iodine co-mediated approach to construct dihydropyrazino[2,3-b]indoles in 2-MeTHF as a green solvent at room temperature was established. A wide range of diversely substituted dihydropyrazino[2,3-b]indoles (42 examples, 61-85% yields) were synthesized under mild conditions, even on a gram scale. This protocol features organocatalysts, an eco-friendly solvent, mild conditions, readily accessible substrates, broad substrate scope and simple work-up.

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.

Novel Scaffolds Based on Bis-thiazole Connected to Quinoxaline or Thienothiophene through 2-Phenoxy-N-arylacetamide Groups as New Hybrid Molecules: Synthesis, Antibacterial Activity, and Molecular Docking Investigations

The resistance of microorganisms to antimicrobials has endangered the health of many people across the world. Overcoming the resistance problem will require the invention of molecules with a new mechanism of action so that no cross-resistance with existing therapies occurs. Because of their powerful antibacterial activity against a wide spectrum of Gram-positive and Gram-negative bacterial strains, heterocyclic compounds are appealing candidates for medicinal chemists. In this regard, as unique hybrid compounds, we synthesized a novel family of bis-thiazoles linked to quinoxaline or thienothiophene via the 2-phenoxy-N-arylacetamide moiety. The target compounds were synthesized by reacting the relevant bis(α-haloketones) with the corresponding thiosemicarbazones in EtOH at reflux with a few drops of TEA. Under comparable reaction conditions, the isomeric bis(thiazoles) were synthesized by reacting the appropriate bis(thiosemicarbazone) with the respective α-haloketones. The structures of the novel compounds were confirmed using elements and spectral data. All of the synthesized compounds were tested for antibacterial activity in vitro. With an inhibitory zone width of 12 mm, compound 12a had the same activity as the reference medication tobramycin against Staphylococcus aureus. Compound 12b showed 20 mg/mL as a minimum inhibitory concentration (MIC) against Bacillus subtilis. Some of the synthesized compounds were tested via molecular docking against two bacterial proteins (dihydrofolate reductase and tyrosyl-tRNA synthetase).

Oxidative (3+3) Cycloaddition/Ring-Opening Reactions of Simple Urea Derivatives and N,N'-Cyclic Azomethine Imines to Construct 1,2,3,5-Tetrazine-4(1H)-one Derivatives

A novel oxidative (3 + 3) cycloaddition/ring-opening reaction of N,N'-cyclic azomethine imines with the in situ generated diaza-oxylallyl cations from simple urea derivatives in the presence of base and PhI(OAc)₂ has been developed. This transformation performs well over a broad substrate scope, which provides facile and rapid access to 1,2,3,5-tetrazine-4(1H)-one derivatives in good yields.

Synthesis, Anti-Potato Virus Y Activities, and Interaction Mechanisms of Novel Quinoxaline Derivatives Bearing Dithioacetal Moiety

Quinoxaline and its derivatives are important functional molecules with a broad range of applications. Disclosed here is a design and synthesis of a series of novel quinoxaline derivatives containing dithioacetal moieties as well as their antiviral activities against potato virus Y (PVY). The compound D30 was developed on the basis of the three-dimensional quantitative structure-activity relationship. The anti-PVY activity test showed that the half maximal effective concentration of the anti-PVY protective activity of compound D30 is 197 μg/mL, which was better than the control agents ningnanmycin (423 μg/mL) and xiangcaoliusuobingmi (281 μg/mL). Significantly, compound D30 can increase defense enzyme activity and chlorophyll content, promote photosynthesis by accelerating carbon fixation in tobacco, and further improve plant disease resistance. All of these results suggest that compound D30 could be employed as a lead compound for novel PVY inhibitor discovery.

One-Pot Construction of Indolo[2,3-b]quinoxalines through Ruthenium-Catalyzed Ortho C-H Bond Functionalization of 2-Arylquinoxalines with Sulfonyl Azides

The synthesis of N-substituted indolo[2,3-b]quinoxalines has been developed through a Ru(II)-catalyzed ortho C-H functionalization of 2-arylquinoxalines with sulfonyl azides and further oxidation with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone in one pot. This double C-N bond formation strategy provides a new efficient route for the preparation of a series of biologically relevant 6H-indolo[2,3-b]quinoxaline derivatives in up to 94% yield, suggesting a broad substrate scope applicability. The preliminary mechanistic studies reveal that the sequential C-N bond formations proceed through the formation of a five-membered ruthenacyclic intermediate in the first step and a radical mechanism in the second step.

Dimeric Drugs

This review intends to summarize the structures of an extensive number of symmetrical-dimeric drugs, having two monomers linked via a bridging entity while emphasizing the large versatility of biologically active substances reported to possess dimeric structures. The largest number of classes of these compounds consist of anticancer agents, antibiotics/antimicrobials, and anti-AIDS drugs. Other symmetrical-dimeric drugs include antidiabetics, antidepressants, analgesics, anti-inflammatories, drugs for the treatment of Alzheimer's disease, anticholesterolemics, estrogenics, antioxidants, enzyme inhibitors, anti-Parkisonians, laxatives, antiallergy compounds, cannabinoids, etc. Most of the articles reviewed do not compare the activity/potency of the dimers to that of their corresponding monomers. Only in limited cases, various suggestions have been made to justify unexpected higher activity of the dimers vs. the corresponding monomers. These suggestions include statistical effects, the presence of dimeric receptors, binding of a dimer to two receptors simultaneously, and others. It is virtually impossible to predict which dimers will be preferable to their respective monomers, or which linking bridges will lead to the most active compounds. It is expected that the extensive number of articles summarized, and the large variety of substances mentioned, which display various biological activities, should be of interest to many academic and industrial medicinal chemists.

Efficient synthetic access to novel indolo[2,3-b]quinoxaline-based heterocycles

BACKGROUND

This paper showed the synthetic capability of the indolo[2,3-b]quinoxaline nucleus to be provided as an excellent precursor for the synthesis of various heterocyclic compounds. These synthetic routes proceed via the formation of 3-(6H-indolo[2,3-b]quinoxalin-6-yl)propane hydrazide (2). The carbohydrazide 2 and its reactions with different reagents give five and six-membered rings, such as 1,3,4-thiadiazole, 1,3,4-oxadiazole, 1,2,4-triazole, and 1,2,4-triazine.

METHODS

All chemicals used in the current study were of analytical grade. Melting points were determined using an APP Digital ST 15 melting point apparatus and were uncorrected. FT-IR spectra were recorded on a Pye-Unicam SP3-100 and Shimadzu-408 spectrophotometers in KBr pellets and given in (cm-1) KBr. The NMR spectra were detected by a Bruker AV-400 spectrometer (400 MHz for 1H, 100 MHz for 13C and 40.55 MHz for 15N), Institute of Organic Chemistry, Karlsruhe, Germany. Chemical shifts were expressed as δ (ppm) with TMS as an internal reference. Mass spectrometry was provided on a Varian MAT 312 instrument in EI mode (70 eV).

RESULTS

The target compounds were obtained, and their structures were completely elucidated by various spectral and elemental analyses (Ft-IR, 1H-NMR, 13C-NMR, and mass spectrometry).

CONCLUSION

The current work showed a view of the reactivity of the carbohydrazide group. The carbohydrazide 2 was obtained from the hydrazinolysis of carboethoxy compound 1 and exploited as a key intermediate to synthesize heterocyclic compounds with different rings.

Recent Updates on the Synthesis of Bioactive Quinoxaline-Containing Sulfonamides

Quinoxaline is a privileged pharmacophore that has broad-spectrum applications in the fields of medicine, pharmacology and pharmaceutics. Similarly, the sulfonamide moiety is of considerable interest in medicinal chemistry, as it exhibits a wide range of pharmacological activities. Therefore, the therapeutic potential and biomedical applications of quinoxalines have been enhanced by incorporation of the sulfonamide group into their chemical framework. The present review surveyed the literature on the preparation, biological activities and structure-activity relationship (SAR) of quinoxaline sulfonamide derivatives due to their broad range of biomedical activities, such as diuretic, antibacterial, antifungal, neuropharmacological, antileishmanial, anti-inflammatory, anti-tumor and anticancer action. The current biological diagnostic findings in this literature review suggest that quinoxaline-linked sulfonamide hybrids are capable of being established as lead compounds; modifications on quinoxaline sulfonamide derivatives may give rise to advanced therapeutic agents against a wide variety of diseases.

Discovery of novel nitrogenous heterocyclic-containing quinoxaline-1,4-di-N-oxides as potent activator of autophagy in M.tb-infected macrophages

As a continuation of our research on antimycobacterial agents, a series of novel quinoxaline-1,4-di-N-oxides (QdNOs) containing various nitrogenous heterocyclic moieties at the R₆ position were designed and synthesized. Antimycobacterial activities, as well as the cytotoxic effects, of the compounds were assayed. Four compounds (6b, 6f, 6n, and 6o), characterized by 2-carboxylate ethyl or benzyl ester, 6-imidazolyl or 1,2,4-triazolyl, and a 7-fluorine group, exhibited the most potent antimycobacterial activity against M.tb strain H37Rv (MIC ≤ 0.25 μg/mL) with low toxicity in VERO cells (SI = 169.3-412.1). Compound 6o also exhibited excellent antimycobacterial activity in an M.tb-infected macrophage model and was selected for further exploration of the mode of antimycobacterial action of QdNOs. The results showed that compound 6o was capable of disrupting membrane integrity and disturbing energy homeostasis in M.tb. Furthermore, compound 6o noticeably increased cellular ROS levels and, subsequently, induced autophagy in M.tb-infected macrophages, possibly indicating the pathways of QdNOs-mediated inhibition of intracellular M.tb replication. The in vivo pharmacokinetic (PK) profiles indicated that compounds 6o was acceptably safe and possesses favorable PK properties. Altogether, these findings suggest that compound 6o is a promising antimycobacterial candidate for further research.

An efficient synthesis of 4-phenoxy-quinazoline, 2-phenoxy-quinoxaline, and 2-phenoxy-pyridine derivatives using aryne chemistry

Herein we report the mild and efficient synthesis of 4-phenoxyquinazoline, 2-phenoxyquinoxaline, and 2-phenoxypyridine derivatives from the starting materials viz. quinazolin-4(3H)-one, quinoxalin-2(1H)-one, and pyridin-2(1H)-one and aryne generated in situ from 2-(trimethylsilyl)phenyl trifluoromethanesulfonate and cesium fluoride. This synthetic methodology gives a new environmentally benign way for the preparation of several unnatural series of 4-phenoxyquinazoline, 2-phenoxyquinoxaline and 2-phenoxypyridine compounds with high yields and broad substrate scope.

Efficient synthesis of 4-phenoxyquinazoline, 2-phenoxyquinoxaline, 2-phenoxypyridine derivatives were generated of aryne from 2-(trimethylsilyl)phenyltrifluoromethanesulfonate with cesium fluoride.

Design, Synthesis, and Biological Evaluation of Novel Thiazolidinone-Containing Quinoxaline-1,4-di-N-oxides as Antimycobacterial and Antifungal Agents

Tuberculosis and fungal infections can pose serious threats to human health. In order to find novel antimicrobial agents, 26 novel quinoxaline-1,4-di-N-oxides containing a thiazolidinone moiety were designed and synthesized, and their antimycobacterial activities were evaluated. Among them, compounds 2t, 2u, 2y, and 2z displayed the most potent antimycobacterial activity against Mycobacterium tuberculosis strain H37Rv (minimal inhibitory concentration [MIC] = 1.56 μg/mL). The antifungal activity of all the compounds was also evaluated against Candida albicans, Candida tropicalis, Aspergillus fumigatus, and Cryptococcus neoformans. Compounds 2t, 2u, 2y, and 2z exhibited potential antifungal activities, with an MIC between 2 and 4 μg/mL. Comparative molecular field analysis (CoMFA: q² = 0.914, r² = 0.967) and comparative molecular similarity index analysis (CoMSIA: q² = 0.918, r² = 0.968) models were established to investigate the structure and antimycobacterial activity relationship. The results of contour maps revealed that electronegative and sterically bulky substituents play an important role in the antimycobacterial activity. Electronegative and sterically bulky substituents are preferred at the C7 position of the quinoxaline ring and the C4 position of the phenyl group to increase the antimycobacterial activity. Additionally, more hydrogen bond donor substituents should be considered at the C2 side chain of the quinoxaline ring to improve the activity.

Synthesis of Dihydrazones as Potential Anticancer and DNA Binding Candidates: A Validation by Molecular Docking Studies

BACKGROUND

Accounting for mortality nearly one in four of human and second highest leading cause of death worldwide. Every year, about 10 million new cancers are diagnosed and causing major health issues in both developing and developed countries.

METHODS

A series of new dihydrazones were synthesized and screened for in vitro anticancer activity against three different MDA-MB-231, A546 and MCF7 cell lines and validated by DNA binding and molecular docking approaches.

RESULT

In the present investigations, synthesized compounds 21, 22, 23 and 24 exhibited potent anticancer activity against tested cancer cell lines and DNA binding study using methyl green comparing to Doxorubicin and ethidium bromide as a positive control respectively.

CONCLUSION

The Structure Activity Relationship (SAR) showed that the electron withdrawing groups (-Cl, -NO2, - F, and -Br) favored the DNA binding studies and anticancer activity whereas, electron donating groups (-OH and - OCH3) showed moderate activity. In the molecular docking study, binding interactions of the most active compounds 21, 22, 23 and 24 stacked with A-T rich regions of the DNA minor groove by surface binding interactions were confirmed. Further, the tuning of active analogs for targeted therapy was warranted.

DNA Structural Alteration Leading to Antibacterial Properties of 6-Nitroquinoxaline Derivatives

Structural integrity of the bacterial genome plays an important role in bacterial survival. Cellular consequences of an intolerable amount of change in the DNA structure are not well understood in bacteria. Here we have stated that binding of synthetic 6-nitroquinoxaline derivatives with DNA led to change in its global structure, subsequently culminating with over-supercoiled form through in-path intermediates. This structural change results in induction of programmed cell death like physiological hallmarks, which is dependent on substitution driven structural modulation properties of the scaffold. A sublethal dose of a representative derivative, 3a, significantly inhibits DNA synthesis, produces fragmented nucleoids, and alters membrane architecture. We have also shown that exposure to the compound changes the native morphology of Staphylococcus aureus cells and significantly disrupts preformed biofilms. Thus, our study gives new insight into bacterial responses to local or global DNA structural changes induced by 6-nitroquinoxaline small molecules.

Effects of an unusual poison identify a lifespan role for Topoisomerase 2 in Saccharomyces cerevisiae

A progressive loss of genome maintenance has been implicated as both a cause and consequence of aging. Here we present evidence supporting the hypothesis that an age-associated decay in genome maintenance promotes aging in Saccharomyces cerevisiae (yeast) due to an inability to sense or repair DNA damage by topoisomerase 2 (yTop2). We describe the characterization of LS1, identified in a high throughput screen for small molecules that shorten the replicative lifespan of yeast. LS1 accelerates aging without affecting proliferative growth or viability. Genetic and biochemical criteria reveal LS1 to be a weak Top2 poison. Top2 poisons induce the accumulation of covalent Top2-linked DNA double strand breaks that, if left unrepaired, lead to genome instability and death. LS1 is toxic to cells deficient in homologous recombination, suggesting that the damage it induces is normally mitigated by genome maintenance systems. The essential roles of yTop2 in proliferating cells may come with a fitness trade-off in older cells that are less able to sense or repair yTop2-mediated DNA damage. Consistent with this idea, cells live longer when yTop2 expression levels are reduced. These results identify intrinsic yTop2-mediated DNA damage as a potentially manageable cause of aging.

Synthesis, Characterization, and Biological Evaluation of Some Novel Quinoxaline Derivatives as Antiviral Agents

Ethyl (6,7-dimethyl-2-oxo-3,4-dihydroquinoxalin-3-yl)acetate and ethyl (6-methyl-2-oxo-3,4-dihydroquinoxalin-3-yl)acetate (1a,b), 3-methylquinoxalin-2(1H)-one (4) and 1,4-dihydroquinoxaline-2,3-dione (11) were the starting precursors for nine novel quinoxaline compounds, 3a, 6, 10, 13, 15, 16, 17, 18, and 20, via adopting different nucleophilic reactions. The synthesized compounds were tested for their antiviral activity against HCV, HBV, HSV-1, and HCMV. Concomitantly, their safety profile was investigated as well as their selectivity against the viral strains. The Virology Unit at the University of Alabama recorded that two compounds, i.e., 1a and 20, exhibited highly potent activity against HCMV with lower IC₅₀ values (<0.05 μM) compared to ganciclovir (IC₅₀  = 0.59 μM). Compounds 1a and 20 also exhibited low cytotoxicity together with a high selectivity index.

Synthesis, cytotoxic evaluation and DNA binding study of 9-fluoro-6H-indolo[2,3-b]quinoxaline derivatives

New quaternary ammonium salts of 9-fluoro-6H-indolo[2,3-b] derivatives were synthesized. These compounds possessed enhanced DNA binding ability and improved antitumor activity.

Synthesis and characterization of azo-guanidine based alcoholic media naked eye DNA sensor

DNA sensing always has an open meadow of curiosity for biotechnologists and other researchers. Recently, in this field, we have introduced an emerging class of molecules containing azo and guanidine functionalities. In this study, we have synthesized three new compounds (UA1, UA6 and UA7) for potential application in DNA sensing in alcoholic medium. The synthesized materials were characterized by elemental analysis, FTIR, UV-visible, 1H NMR and 13C NMR spectroscopies. Their DNA sensing potential were investigated by UV-visible spectroscopy. The insight of interaction with DNA was further investigated by electrochemical (cyclic voltammetry) and hydrodynamic (viscosity) studies. The results showed that compounds have moderate DNA binding properties, with the binding constants range being 7.2 × 103, 2.4 × 103 and 0.2 × 103 M-1, for UA1, UA6 and UA7, respectively. Upon binding with DNA, there was a change in colour (a blue shift in the λmax value) which was observable with a naked eye. These results indicated the potential of synthesized compounds as DNA sensors with detection limit 1.8, 5.8 and 4.0 ng µl-1 for UA1, UA6 and UA7, respectively.

An Alternative Approach to the Synthesis of New Pyrimido[5′,4′:5,6][1,4] Thiazino[2,3-B]Quinoxaline Derivatives

An alternative approach to the synthesis of a series of new pyrimido[5′,4′:5,6][1,4]thiazino[2,3-b]quinoxaline derivatives is described. Reaction of 5-bromo-2,4-dichloro-6-methylpyrimidine and 3-aminoquinoxaline-2-thiol leads to the key intermediate 3-[(5-bromo-2-chloro-6-methylpyrimidin-4-yl)thio]quinoxalin-2-amine. This intermediate can be transformed into the title ring systems by subsequent treatment either with secondary amines followed by intramolecular cyclisation or initial intramolecular cyclisation with subsequent reaction with secondary amines.

Synthesis, Characterization, and Pharmacological Evaluation of Selected Aromatic Amines

Aromatic amines 1-amino-4-phenoxybenzene (A-1A), 2-(4-aminophenoxy) naphthalene (A-2A), and 1-(4-aminophenoxy) naphthalene (A-3A) were synthesized by the reduction of corresponding nitroaromatics with hydrazine monohydrate and Pd/C 5% (w/w). The newly synthesized compounds were characterized by FTIR,1H NMR,13C NMR, UV-visible spectrophotometer, and mass spectrometry and their biological activities were investigated along with structurally similar 4-(4-aminophenyloxy) biphenyl (A-A). Results of brine shrimp cytotoxicity assay showed that almost all of the compounds had LD50values <1 μg/mL. The compounds also showed significant antitumor activity with IC50values ranging from 67.45 to 12.2 µgmL−1. The cytotoxicity and antitumor studies correlate the results which suggests the anticancerous nature of compounds. During the interaction study of these compounds with DNA, all of the compounds showed hyperchromic effect indicating strong interaction through binding with the grooves of DNA. Moreover, A-3A also showed decrease inλmaxconfirming higher propensity for DNA groove binding. In DPPH free radical scavenging assay, all the compounds showed potential antioxidant capability. The compounds were highly active in protecting DNA against hydroxyl free radicals. DNA interaction and antioxidant results back up each other indicating that these compounds have potential to be used as cancer chemopreventive agents. Additionally, one compound (A-1A) showed significant antibacterial and antifungal activity as well.

Cu(i) complex based on 6H-indolo[2,3-b]quinoxaline: structure and electrocatalytic properties for hydrogen evolution reaction from water

A Cu(i) complex can act as an electrochemically stable electrocatalyst for the hydrogen evolution reaction, which can improve the exchanging current density with ca. 40 kJ mol⁻¹ of E_a from 30 to 50 °C.

A Green Synthesis of Indolo[2,3-b]Quinoxaline Derivatives

A simple, efficient and eco-friendly synthesis of a series of structurally new indolo[2,3- b]quinoxaline derivatives has been developed. The synthesis mainly relies on the condensation reaction of various isatins with o-phenylenediamine in water with the use of benzyltriethylammonium chloride as catalyst. The protocol is very simple, avoids toxic solvents and catalysts, is easy to work-up and is thus especially ‘green’.

Design, synthesis, antifungal, and antioxidant activities of (E)-6-((2-phenylhydrazono)methyl)quinoxaline derivatives

Different substituted phenylhydrazone groups were linked to the quinoxaline scaffold to provide 26 compounds (6a-6z). Their structures were confirmed by (1)H and (13)C NMR, MS, elemental analysis, and X-ray single-crystal diffraction. The antifungal activities of these compounds against Rhizoctonia solani were evaluated in vitro. Compound 6p is the most promising one among all the tested compounds with an EC50 of 0.16 μg·mL(-1), more potent than the coassayed positive control fungicide carbendazim (EC50: 1.42 μg·mL(-1)). In addition, these compounds were subjected to antioxidant assay by employing diphenylpicrylhydrazyl (DPPH) and mice microsome lipid peroxidation (LPO) methods. Most of these compounds are potent antioxidants. The strongest compounds are 6e (EC50: 7.60 μg·mL(-1), DPPH) and 6a (EC50: 0.96 μg·mL(-1), LPO), comparative to or more potent than the positive control Trolox [EC50: 5.90 μg·mL(-1) (DPPH) and 18.23 μg·mL(-1) (LPO)]. The structure and activity relationships were also discussed.