Biomedical application of graphitic carbon nitrides: tissue depositionin vivo, induction of reactive oxygen species (ROS) and cell viability in tumor cells.

The urgency for new materials in oncology is immediate. In this study we have developed the g-C3N4, a graphitic-like structure formed by periodically linked tris-s-triazine units. The g-C3N4has been synthesized by a simple and fast thermal process. XRD has shown the formation of the crystalline sheet with a compacted structure. The graphite-like structure and the functional groups have been shown by Raman and FTIR spectroscopy. TEM image and AFM revealed the porous composed of five or six C-N layers stacked. DRS and Photoluminescence analyses confirmed the structure with band gap of 2.87 eV and emission band at 448 nm in different wavelengths excitation conditions. The biological results showed inhibitory effect on cancer cell lines and non-toxic effect in normal cell lines. To the best of our knowledge, this is the first work demonstrating the cytotoxic effects of 2D g-C3N4in a cancer cell line, without any external or synergistic influence. The biodistribution/tissue accumulation showed that g-C3N4present a tendency to accumulation on the lung in the first 2 h, but after 24 h the profile of the biodistribution change and it is found mainly in the liver. Thus, 2D-g-C3N4showed great potential for the treatment of several cancer types.

Highly Dispersed Nanocomposite of AgBr in g-C3N4 Matrix Exhibiting Efficient Antibacterial Effect on Drought-Resistant Pseudomonas putida under Dark and Light Conditions.

Synthesis of nanocomposites possessing intimately mixed components is highly challenging to bring out the best possible properties of the materials. The challenge is mainly due to the difficulties associated with controlling the phase segregation of individual components as a result of high interfacial tension between them and cohesive forces within each component during the synthesis. Here, we show a single-step synthesis of representative nanocomposites of g-C3N4/AgBr through a rationally designed approach, wherein melamine, the precursor of g-C3N4, has been intimately mixed with the AgBr precursor, silver-tetraoctylammonium bromide. Subsequent calcination of the obtained solid at 500 °C has resulted in the formation of highly dispersed g-C3N4/AgBr. The key to such a high dispersion lies in the surfactant-based AgBr precursor that minimized the interfacial tension during the process. The AgBr content has been varied between 2 and 20 wt % with respect to the g-C3N4 content. The obtained nanocomposites have been thoroughly characterized using XRD, XPS, ED-XRF, FE-SEM, HR-TEM, DRS, TCSPC, and BET surface area techniques. The studies revealed a high dispersion of AgBr in the g-C3N4 matrix. The nanocomposites have been found to exhibit remarkable antimicrobial properties over a drought-resistant bacterial strain of Pseudomonas putida under both dark and light conditions compared with similar compositions obtained through other methods reported so far. The present study offers a new approach for synthesizing highly dispersed and efficient nanocomposites.

Synthesis and biomedical applications of graphitic carbon nitride quantum dots.

Graphitic carbon nitride quantum dots (g-CNQDs) have attracted much attention for biomedical applications by virtue of their good biocompatibility, stable fluorescence, high quantum yield, and nontoxicity. On the basis of understanding the intrinsic properties and structural features in the intriguing system, enormous efforts have been devoted to optimizing synthetic methods and structures of g-CNQDs. A vast number of studies have also been pursued to discuss the potential applications of g-CNQDs in biomedical areas for biosensing, bioimaging, drug delivery and theranostics. In this review, we summarize the recent advances and applications and address the future challenges and opportunities of these g-CNQDs in the biomedical field.

Hemin-porous g-C3N4 hybrid nanosheets as an efficient peroxidase mimic for colorimetric and visual determination of glucose.

A method is described for colorimetric determination of glucose by using hemin-porous graphitic carbon nitride (g-C3N4) hybrid nanosheets as a peroxidase mimic. The porous g-C3N4 nanosheets were prepared by a combination of one-pot self-polymerization, pyrolysis and liquid-phase exfoliation. The hemin-porous g-C3N4 hybrid nanosheets were prepared via in-situ deposition. It is shown that the hybrid composite has improved dispersibility, stability, and peroxidase-mimicking activity in the 3,3',5,5'-tetramethylbenzidine (TMB)/H2O2 system. This is deemed to be the result of the synergistic effect of hemin and porous g-C3N4 nanosheets. Based on these advantages of the nanosheets, a simple, low-cost, sensitive and selective colorimetric method was established for the determination of glucose at pH values around 7. Best performed at a wavelength of 652 nm, the assay has a linear response in the 10.0 µM to 500 µM glucose concentration range (R2 = 0.9942) and a 1.94 µM limit of detection. This method was successfully applied to the determination of glucose in (spiked) human serum samples. In our perception, the hybrid is a robust peroxidase mimic for use in POx-based assays as needed in medical diagnosis and environmental analysis. Graphical abstract Schematic presentation of the process of hemin-porous g-C3N4 hybrid nanosheets catalyzing the oxidation of peroxidase chromogenic substrate tetramethylbenzidine (TMB) in the presence of H2O2. The material was applied in colorimetric and visual determination of H2O2 and glucose.

Exploitation of the Ugi-Joullié reaction in drug discovery and development.

Introduction: Multicomponent reactions are paramount in drug discovery for their ability to achieve high levels of diversity within the chemical space, generating complex structures from simple building blocks. Among them, the isocyanide-based Ugi-Joulliè reaction is particularly suited for the rapid synthesis of peptidomimetics and nitrogen-containing compounds. Areas covered: The latest achievements in drug discovery and synthetic chemistry regarding the application of the Ugi-Joulliè reaction in the field of natural compounds, peptidomimetics and small molecules, are reported in this article. All relevant literature was disclosed applying most common web-based literature searching tools, namely Web of Science, PubMed, SciFinder and Google Scholar. Expert opinion: The Ugi-Joulliè reaction represents an extremely versatile and simple synthetic methodology, useful for designing efficiently new molecular frameworks. Particularly relevant to drug discovery is the Ugi-Joulliè-based synthesis of conformationally constrained peptidomimetics and antibacterial depsipeptides. On the other hand, the many syntheses of new, nitrogen-containing heterocycles are not always followed by biological evaluation, losing opportunities for the disclosure of unprecedented lead compounds.

New Nitrogen Compounds Coupled to Phenolic Units with Antioxidant and Antifungal Activities: Synthesis and Structure⁻Activity Relationship.

A selection of 1-amino-2-arylidenamine-1,2-(dicyano)ethenes 3 was synthesized and cyclized to 2-aryl-4,5-dicyano-1H-imidazoles 4 upon reflux in ethyl acetate/acetonitrile, in the presence of manganese dioxide. These compounds were tested for their antioxidant capacity by cyclic voltammetry, 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical and deoxyribose degradation assays. The minimum inhibitory concentration of all compounds was evaluated against two yeast species, Saccharomyces cerevisiae and Candida albicans. Their toxicity was tested in mammal fibroblasts. Among the synthesised compounds, two presented dual antioxidant/antifungal activity without toxic effects in fibroblasts. The new compounds synthesized in this work are potential biochemical tools and/or therapeutic drugs.

[Development of Novel Preparations for Nitrogen Heterocycles Based on Cascade Reactions].

　Nitrogen heterocycles are important skeletons in biologically active compounds such as medicines and natural alkaloids. However, in terms of the efficiency of the synthetic process, the many synthetic steps required to achieve the target compounds with complex architectures pose a significant problem. To overcome this challenge, novel approaches were developed to afford biologically active heterocycles, 1,2-diazepines, pyrroloisoquinolines, and pyrrolizidines utilizing cascade reactions that enable multiple bond formation in a one-pot process. This review discusses three one-pot reactions: 1) 1,2-diazepine synthesis from cyclobutenones and lithiodiazoesters via cascade 4π-8π electrocyclization; 2) synthesis of pyrroloisoquinolines from alkynylimino esters triggered by gold-catalyzed azomethine ylide formation; and 3) pyrrolizidine synthesis via three-component coupling reactions of iminoesters, acetylenes, and maleimides through the gold-catalyzed azomethine ylide generation/[3+2]-cycloaddition/enamine cyclization reaction.

In situ synthesis of g-C3N4/TiO2 heterojunction nanocomposites as a highly active photocatalyst for the degradation of Orange II under visible light irradiation.

As a highly active photocatalyst, g-C3N4/TiO2 heterojunction nanocomposites were in situ synthesized by simple ultrasonic mixing and calcination by using TiO2 and melamine as precursors. The morphology and structure of the prepared photocatalysts were characterized by field emission scanning electron microscopy, transmission electron microscopy, X-ray diffraction, Fourier-transform infrared spectroscopy, UV-Vis diffuse reflectance spectroscopy, and X-ray photoelectron spectroscopy. The photocatalytic activities of g-C3N4/TiO2 nanocomposites to degrade Orange II (AO7) under visible light irradiation were evaluated. Results showed that the photocatalytic rate of the prepared g-C3N4/TiO2 photocatalyst to degrade AO7 was about three times than that of pristine TiO2 and g-C3N4. The g-C3N4/TiO2 composite with a ratio of 1:4 had the highest degradation efficiency for AO7 solution. Its degradation efficiency under acidic conditions was significantly higher than that under alkaline conditions. The enhancement of photocatalytic activity can be attributed to the formation of heterojunctions between g-C3N4 and TiO2, which leads to rapid charge transfer and the efficient separation of photogenerated electron-hole pairs. The recycling experiment indicated that the photocatalyst of g-C3N4/TiO2 nanocomposites still maintained good photochemical stability and recyclability after five cycles; this finding was important for its practical applications. A series of free radical trapping experiments showed that •O2- played a crucial role in the degradation of AO7. Graphical Abstract ᅟ.

Five- and Six-Membered Nitrogen-Containing Compounds as Selective Carbonic Anhydrase Activators.

It has been proven that specific isoforms of human carbonic anhydrase (hCA) are able to fine-tune physiological pathways connected to signal processing, and that decreased CAs expression negatively influences cognition, leading to mental retardation, Alzheimer's disease, and aging-related cognitive dysfunctions. For this reason, a small library of natural and synthetic nitrogen containing cyclic derivatives was assayed as activators of four human isoforms of carbonic anhydrase (hCA I, II, IV and VII). Most of the compounds activated hCA I, IV and VII in the micromolar range, with KAs ranging between 3.46 and 80.5 µM, whereas they were not active towards hCA II (KAs > 100 µM). Two natural compounds, namely l-(+)-ergothioneine (1) and melatonin (2), displayed KAs towards hCA VII in the nanomolar range after evaluation by a CO2 hydration method in vitro, showing a rather efficient and selective activation profile with respect to histamine, used as a reference compound. Corroborated with the above in vitro findings, a molecular modelling in silico approach has been performed to correlate these biological data, and to elucidate the binding interaction of these activators within the enzyme active site.

Therapeutic Potential of N-heterocyclic Analogs as Anti-inflammatory Agents.

BACKGROUND: Various mediators and anti-inflammatory drugs were used since from a long time but it is still a challenge for the medicinal chemists to treat or reduce the symptoms of inflammatory diseases. Most of the clinically used anti-inflammatory drugs such as NSAIDs, Coxibs and GCs are allied with considerable toxicity. OBJECTIVE: The search of novel anti-inflammatory agent is not an ending process. Although the drug treatment has been improved steadily but yet, it is still there is a need to develop more potent therapeutic agents. METHOD: Reported literature survey has been studied to summarize the nitrogen containing moieties which were utilized as potential therapeutic agents. RESULTS: A variety of N-heterocyclic analogs are known to exhibit a wide range of interesting biological activities like antioxidant, anti-inflammatory, anticonvulsant, analgesic, antimicrobial, anticancer, antiprotozoal, antioxidant, antiparasitic, antiplatelet, cardioprotective, anthelmintic, antidiabetic, antitubercular, trypanocidal and anti-HIV. However, numerous approaches were used to overcome the toxicity level such as co-administration with suitable agent/substance which provides protection against toxicity as well to synthesise new potent and safe anti-inflammatory drug. CONCLUSION: The present review summarizes the synthetic methodology and therapeutic potential of some N-heterocyclic analogs as potent anti-inflammatory agents.

Nitrogen-functionalized Isohexides in Asymmetric Induction.

Biosourced isohexides have attracted the considerable attention of both the academic and industrial chemistry communities over the last 50 years. This highlight focuses on the synthesis of nitrogen-containing isohexides and their applications in asymmetric catalysis.

Formation of cyanogen iodide by lactoperoxidase.

The haem protein lactoperoxidase (LPO) is an important component of the anti-microbial immune defence in external secretions and is also applied as preservative in food, oral care and cosmetic products. Upon oxidation of SCN(-) and I(-) by the LPO-hydrogen peroxide system, oxidised species are formed with bacteriostatic and/or bactericidal activity. Here we describe the formation of the inter(pseudo)halogen cyanogen iodide (ICN) by LPO. This product is formed when both, thiocyanate and iodide, are present together in the reaction mixture. Using (13)C nuclear magnetic resonance spectroscopy and gas chromatography-mass spectrometry we could identify this inter(pseudo)halogen after applying iodide in slight excess over thiocyanate. The formation of ICN is based on the reaction of oxidised iodine species with thiocyanate. Further, we could demonstrate that ICN is also formed by the related haem enzyme myeloperoxidase and, in lower amounts, in the enzyme-free system. As I(-) is not competitive for SCN(-) under physiologically relevant conditions, the formation of ICN is not expected in secretions but may be relevant for LPO-containing products.

Phosphorus-nitrogen compounds. Part 29. Syntheses, crystal structures, spectroscopic and stereogenic properties, electrochemical investigations, antituberculosis, antimicrobial and cytotoxic activities and DNA interactions of ansa-spiro-ansa cyclotetraphosphazenes.

A number of novel ansa-spiro-ansa (asa) cyclotetraphosphazenes (1a-5b) was prepared in the range of 63-90 % yields. The structures of the compounds were verified by MS, FTIR, (1)H, (13)C{(1)H} and (31)P{(1)H} NMR, heteronuclear single quantum coherence (HSQC), and heteronuclear multiple-bond correlation (HMBC) techniques. The crystal structures of 1b, 2c and 5a were determined by X-ray crystallography. The compound 2c was analyzed by the changes in the (31)P{(1)H}NMR spectrum in addition of the chiral solvating agent; (R)-(+)-2,2,2-trifluoro-1-(9'-anthryl)-ethanol (CSA), to investigate its stereogenic properties. The result supports that compound 2c was found to be in the racemic mixture. Cyclic voltammetric and chronoamperometric data of the mono-ferrocenyl-spiro-asa-cyclotetraphosphazenes exhibited electrochemically reversible one-electron oxidation of Fe redox centres. The mono-ferrocenyl-spiro-asa compounds (3a-5b) were evaluated for antituberculosis activity against reference strain Mycobacterium tuberculosis H37Rv and M. tuberculosis clinical strain, which is resistant to rifampicin and isoniazid. These compounds appear not to be good candidates for being antituberculosis agents to clinical strains. All of the compounds were screened for antibacterial activities against G(+) and G(-) bacteria, and for antifungal activities against yeast strains. They seem to be more active against Gram positive bacteria than Gram negative. The interactions of the phosphazenes with plasmid DNA and the evaluations for cytotoxic activity against MCF-7 breast cancer cell lines were investigated. The compounds 1b, 2b, 3a and 4a were found to be more effective than Cisplatin against MCF-7 breast cancer cell lines at lower concentrations.

Theoretical studies on the stability, detonation performance and possibility of synthesis of the nitro derivatives of epoxyethane.

Compounds with heterocyclic rings and NO2 groups have drawn much attention as high energy density compounds in recent years. In this study, the nitro derivatives 1-4 of epoxyethane (ETO) were investigated, and their synthetic possibilities in thermodynamics and thermal stability were predicted. The trigger bond for 1, 2 and 3 is the C-C bond, but for 4 it is the C-NO2 bond. The bond dissociation energies (EBDs) were estimated to be 205.40-164.86 kJ mol(-1) and h 50s were 53-126 cm. EBD, h 50 and energy gap all decrease from 1 to 4. A linear relationship exists between the strain energy and the number of the NO2 group. Derivative 2 has a zero oxygen balance and possesses the best detonation properties (D=8.77 km s(-1) and P=33.88 GPa) as a single explosive. Derivatives 3 and 4 used as oxidizers in the composite explosives of hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) produce very good detonation performance (D=9.36 km s(-1), P=40.15 GPa and I s = 281.56 s for 3/RDX, and D=9.45 km s(-1), P=41.04 GPa and I s=280.34 s for 4/RDX). The intermolecular hydrogen bonding and dispersion interactions of 3/RDX and 4/RDX show that the compatibilities of these composites are acceptable.

Synthesis, biological evaluation, and computational studies of Tri- and tetracyclic nitrogen-bridgehead compounds as potent dual-acting AChE inhibitors and hH3 receptor antagonists.

Combination of AChE inhibiting and histamine H3 receptor antagonizing properties in a single molecule might show synergistic effects to improve cognitive deficits in Alzheimer's disease, since both pharmacological actions are able to enhance cholinergic neurotransmission in the cortex. However, whereas AChE inhibitors prevent hydrolysis of acetylcholine also peripherally, histamine H3 antagonists will raise acetylcholine levels mostly in the brain due to predominant occurrence of the receptor in the central nervous system. In this work, we designed and synthesized two novel classes of tri- and tetracyclic nitrogen-bridgehead compounds acting as dual AChE inhibitors and histamine H3 antagonists by combining the nitrogen-bridgehead moiety of novel AChE inhibitors with a second N-basic fragment based on the piperidinylpropoxy pharmacophore with different spacer lengths. Intensive structure-activity relationships (SARs) with regard to both biological targets led to compound 41 which showed balanced affinities as hAChE inhibitor with IC50 = 33.9 nM, and hH3R antagonism with Ki = 76.2 nM with greater than 200-fold selectivity over the other histamine receptor subtypes. Molecular docking studies were performed to explain the potent AChE inhibition of the target compounds and molecular dynamics studies to explain high affinity at the hH3R.

Synthesis and reactivity of a transient, terminal nitrido complex of rhodium.

Irradiation of rhodium(II) azido complex [Rh(N3){N(CHCHPtBu2)2}] allowed for the spectroscopic characterization of the first reported rhodium complex with a terminal nitrido ligand. DFT computations reveal that the unpaired electron of rhodium(IV) nitride complex [Rh(N){N(CHCHPtBu2)2}] is located in an antibonding Rh-N π* bond involving the nitrido moiety, thus resulting in predominant N-radical character, in turn providing a rationale for its transient nature and observed nitride coupling to dinitrogen.

C-N bond forming cross-coupling reactions: an overview.

Nitrogen containing compounds are of great importance because of their interesting and diverse biological activities. The construction of the C-N bond is of significant importance as it opens avenues for the introduction of nitrogen in organic molecules. Despite significant advancements in this field, the construction of the C-N bond is still a major challenge for organic chemists, due to the involvement of harsh reaction conditions or the use of expensive catalysts in many cases. Thus, it is a challenge to develop alternative, milder and cheaper methodologies for the construction of C-N bonds. Herein, we have selected some prime literature reports that may serve this purpose.

Submerged liquid plasma for the synthesis of unconventional nitrogen polymers.

Glow discharge polymerization is not well understood due to the rapid/complex reaction at the plasma/gas precursor interface. Plasma reaction in a submerged condition allows post-plasma-polymerization, leading to further polymer growth and thus a stable structure. Electron collision with acetonitrile at the interface initiates the formation of radical monomers, which undergoes further rearrangement to form low-molecular (LM) nitrogen polymers (NPs). The radical-rich LM NPs go through further polymerization, forming stable high-molecular (HM) NPs (as determined using liquid chromatography/mass spectrometry). LM NPs absorb light at a wavelength of 270 nm (λ max) whereas HM NPs show absorption at 420 nm (λ max), as determined from ultraviolet-visible absorption spectra. The fluorescence spectra of HM NPs show characteristic emission at 430 nm, which indicates the presence of nitrogen functional groups with external conjugation. The proposed structure of HM NPs is verified with different analytical instruments.

Pyrolysis of high-ash sewage sludge in a circulating fluidized bed reactor for production of liquids rich in heterocyclic nitrogenated compounds.

A circulating fluidized bed reactor was used for pyrolyzing sewage sludge with a high ash content to produce liquids rich in heterocyclic nitrogenated compounds. GC/MS and FTIR analyses showed that heterocyclic nitrogenated compounds and hydrocarbons made up 38.5-61.21% and 2.24-17.48% of the pyrolysis liquids, respectively. A fluidized gas velocity of 1.13 m/s, a sludge feed rate of 10.78 kg/h and a particle size of 1-2mm promoted heterocyclic nitrogenated compound production. Utilizing heterocyclic nitrogenated compounds as chemical feedstock could be a way for offsetting the cost of sewage sludge treatment.

Highly efficient asymmetric Michael addition of aldehyde to nitroolefin using perhydroindolic acid as a chiral organocatalyst.

Perhydroindolic acids, the by-products obtained in the industrial production of a trandolapril intermediate, were used as chiral organocatalysts in asymmetric Michael addition reactions of aldehydes to nitroolefins. These proline-like catalysts are unique for their rigid bicyclic structure with two H atoms attached to the bridgehead C atoms lying on the opposite side of the ring. They therefore showed high efficiency in asymmetric Michael additions of aldehydes to nitroolefins. Under the optimal conditions, excellent diastereo- and enantioselectivities (up to 99/1 dr and 98% ee) were obtained with high chemical yields for a series of aldehydes and nitroolefins using only 5 mol% catalyst loading. The methodology features easily available catalysts, high catalytic efficiency and environmentally green procedures.