Stable Oxidants Research Articles

Identification of Isoliensinine as a Ferroptosis Suppressor with Iron-Chelating Activity.

Ferroptosis is a type of regulated cell death driven by the iron-dependent accumulation of lipid peroxides. The high involvement of ferroptosis in diverse human diseases highlights the need for the identification of new chemotypes with anti-ferroptotic activity. Here, we performed a natural product library screening in HT1080 fibrosarcoma cells and identified licochalcone A (LA), isoeugenyl acetate (ISA), and isoliensinine (ISL) as suppressors of either RSL3- or IKE-induced ferroptosis. Mechanistically, ferroptosis resistance conferred by these compounds is mainly through GPX4/NRF2-independent mechanisms. Among them, only ISL could effectively rescue ferroptosis induced by FINO2, which is a stable oxidant of ferrous iron, suggesting that ISL may have the properties of an iron chelator. Consistent with the hypothesis, both computational tools and X-ray photoelectron spectroscopy supported the binding between ISL and iron ions. And ISL greatly inhibited excessive iron-dependent ferroptotic cell death through limiting intracellular iron accumulation. Furthermore, its iron chelator activity also protected mice from organ injury in an acute iron overload model. In conclusion, this study provided valuable insights for developing effective anti-ferroptosis agents from natural products, which represent a potential therapeutic strategy for treating ferroptosis-associated organ damage.

Highly selective oxidation of 3,7-dichloro-8-dichloro methyl quinoline toward quinclorac by CoPc-Mn-Br catalytic system

Nowadays, the use of quinoline derived synthons as precursors of quinclorac products is an important research topic in green chemistry. O2 is a cheap, stable, and eco-friendly oxidant, holding promise for organic oxidation reactions. Herein, we have pioneered the discovery of CoPc-Mn(OAc)2-HBr (CoPc-Mn-Br) catalyst system for the selective oxidation of 3,7-dichloro-8-dichloro methyl quinoline (3,7-D-8-DMQ) into quinclorac with high 3,7-D-8-DMQ conversion at 59.3 %. The CoPc-Mn-Br exhibits excellent selectivity of quinclorac (up to 60.3 %), affording high quinclorac yield of 35.7 %, which is 3.1-fold higher than the yield of Co(OAc)2-Mn(OAc)2-HBr (Co-Mn-Br). Electron paramagnetic resonance (EPR) investigations and density functional theory (DFT) calculations indicate that CoPc promotes the adsorption and activation of O2 in this oxidation process, which generates more Co3+, leading to producing the reactive intermediate species 3,7-dichloro-8-carbonyl quinoline free radicals via the radical process. The insight achieved from this fundamental study may be further applied to other organic syntheses via selective oxidation.

A low-cost magnetic catalyst (MnFe2O4) for ciprofloxacin degradation via periodate activation: The synergistic effect of Mn and Fe

The treatment of water pollution caused by excessive usage of antibiotics has been widely concerned. Periodate (PI)-oxidation method poses a good application prospect for antibiotic degradation with a stable solid oxidant and excellent degradation efficiency. In this study, manganese ferrite (MnFe2O4) with superparamagnetic property, low ion leaching, and outstanding activation performance was chosen to active PI to remove ciprofloxacin (CIP) for the first time. And MnFe2O4/PI system could achieve 98.8% removal efficiency of 10 mg/L CIP in 90 min (pH = 5.4, 0.3 g/L MnFe2O4, 0.2 g/L PI). With the conversion of Fe(II)/Fe(III) and Mn(II)/Mn(III)/Mn(Ⅳ), singlet oxygen (1O2), iodate radical (IO3•), and superoxide radical (O2•−) were formed as the primary active substances to remove CIP. Meanwhile, the redox cycle of Fe(III)/Fe(II) (0.77 V) and Mn(Ⅳ)/Mn(III) (0.15 V) accelerated the process of CIP degradation. Almost 90% of CIP could be removed by MnFe2O4/PI system after 5th run, showing the excellent stability of MnFe2O4 to activate PI. Besides, MnFe2O4/PI system showed tolerance to different background water and selectivity to different antibiotics. This work presents a novel strategy to integrate MnFe2O4 with PI for antibiotic-polluted water treatment.

Treatment of sewage sludge hydrothermal carbonization aqueous phase by Fe(II)/CaO2 system: Oxidation behaviors and mechanism of organic compounds

The Fe(II)/CaO2 system with a stable oxidant and a low-cost homogeneous activating agent has been considered as a prospective process for the disposal of wastewater. The system was constructed to treat sewage sludge hydrothermal carbonization aqueous phase (HTC-AP) in this study. As the hydrothermal temperature increased, the organics in the HTC-AP were first decomposed and then cyclized, while the Maillard reaction occurs throughout the stage. The oxidation efficiency of the Fe(II)/CaO2 system was related to the composition of organics in HTC-AP, and the removal of dissolved organic carbon (DOC) by the system was 38.56 % in the HTC-AP obtained by hydrothermal treatment at 220 °C. Redundancy analysis showed that the low molecular weight organics, hydrophobic acids, and hydrophobic neutral components were beneficial to DOC removal, while Maillard products and cyclization products were hard to be oxidized to CO2 and H2O. The CN functional group of the protein facilitated DOC removal, and some organics in HTC-AP were oxidized to acids and phenols. The energy input to remove DOC in Fe(II)/CaO2 system was 27.74 MJ per kg carbon. This study provides a low-energy consumption Fe(II)/CaO2 system for the post-treatment of HTC-APs and explores the applicability of the system.

A new β-cyclodextrin-encapsulated potassium ferrate composite (KFO@β-CD) for efficient removal of PPCPs from reclaimed water: Performance and degradation pathway

Ferrate is increasingly used as an oxidant for chemical oxidation of pharmaceuticals and personal care products (PPCPs) in reclaimed water. However, the instability of ferrate in aqueous solution and its low content of active ingredients have limited its application in water purification. In this paper, a novel β-cyclodextrin encapsulated potassium ferrate composite (KFO@β-CD) is synthesized for the first time using a thermomelting-condensation method and used to degrade carbamazepine (CBZ). This study evaluates and demonstrates the superior stability, sustained release behavior and hygroscopic characteristics of KFO@β-CD. In-depth investigations show that KFO@β-CD with a mass ratio of 10:1 can degrade 85.2 % of CBZ in 60 min. Analyzing the transformation pathways of CBZ has shown that Fe(VI) performed more reactive with olefinic double bond owing to electron-rich organic moieties, which convert carbamazepine to oxidized products with low molecular weight. These results significantly improve the state of our knowledge about this highly efficient and stable oxidant, which is likely to be useful for further degradation of PPCPs.

해수 오존처리시 브로민 생성과 소독효과

Pathogenic and/or invasive organisms are problematic in ballast water, desalination plants and aquaculture systems for both ecological and economic reasons. In a desalination plant, the presence of microorganisms can lead to biofouling of the ultrafiltration and seawater reverse osmosis membrane equipment. Meanwhile, in the aquaculture industry, some pathogenic organisms cause serious fish diseases, which can result in mass die-offs. Various disinfection techniques such as ozonation, ultraviolet irradiation, electrolysis and chlorination, have been applied to remove pathogenic organisms from seawater environments. The purpose of this study was to develop a kinetic model for the prediction of residual ozone and bromine concentrations in seawater following ozonation, taking into consideration the ozone dose, water salinity, and pH. Ozone chemistry in saltwater is considerably different from that in fresh water because saltwater contains much higher concentrations of dissolved anions and cations (e.g., chloride, bromide, magnesium, sulfate) than fresh water. Salinity greatly affects the formation of residual ozone and bromine during saltwater ozonation. Unlike freshwater ozonation, there is no hydroxyl radical formation in seawater ozonation because ozone decomposition is considerably faster in water containing bromide. Therefore, seawater ozonation involves the initial unstable oxidant (ozone) and a secondary, more stable oxidant (bromine) for disinfection. This study also aimed to evaluate the performance of ozone and bromine disinfection using E. coli. The log inactivation of E. coli with ozone and bromine was 2.5 and 4 log, respectively. The log inactivation of E. coli with seawater ozonation was 5.8 log.

Silicon nanowire-based energetic materials with significantly improved hygroscopicity

The large energy release potential and highly adjustable combustion characteristics of nanostructured silicon compounded with sodium perchlorate (NaClO4) make it one of the most attractive inorganic energetic materials. Compared with nanoporous silicon, the silicon nanowires prepared by metal-assisted chemical etching are easily loaded with NaClO4 to obtain energetic materials, due to their one-dimensional array structure and tight contact with the silicon substrate. However, the high hygroscopicity of NaClO4 greatly degrades the long-term storage property of the material, and must be addressed. In this study, sulfur, as a known stable and non-hygroscopic oxidant that reacts with nanostructured silicon, was impregnated on the silicon nanowires/NaClO4 energetic material to insulate NaClO4 from H2O in the ambient air. After sulfur impregnation, the mass of the sample increased by 8.7 ​mg after being exposed to 98% relative humidity at 25 ​°C for 12 ​h, while the sample without sulfur increased by 50 ​mg, indicating significant improvement in the hygrophobicity of the sulfur-containing energetic material. Laser ignition experiments showed that the combustion performance was only slightly affected after sulfur treatment. This work provides a new strategy for improving the hygrophobicity of silicon-based energetic materials, which can improve their applicability in micro-electromechanical systems.

Photo-induced sp3 C-H bond arylation, cyanation and nitroalkylation of tetrahydroisoquinolines (THIQs) under visible light irradiation using a combination of NHPI and Rose Bengal.

This work reports a sustainable protocol for α-arylation of tetrahydroisoquinolines (THIQs) with aryl diazonium salts using a combination of a cheap and stable oxidant, N-hydroxyphthalimide (NHPI), and an inexpensive dye photosensitizer, Rose Bengal (RB), for the first time. The reaction was performed at ambient temperature using green LED light irradiation under an oxygen atmosphere. The developed α-arylation protocol shows a diverse substrate scope for various THIQs and aryl diazonium salts. The work also explores nitroalkylation and cyanation under the developed reaction conditions. A possible SET mechanism is involved which was confirmed by ESI-MS analysis of the reaction mixture.

Oxidative Stress Product, 4-Hydroxy-2-Nonenal, Induces the Release of Tissue Factor-Positive Microvesicles From Perivascular Cells Into Circulation.

TF (Tissue factor) plays a key role in hemostasis, but an aberrant expression of TF leads to thrombosis. The objective of the present study is to investigate the effect of 4-hydroxy-2-nonenal (HNE), the most stable and major oxidant produced in various disease conditions, on the release of TF+ microvesicles into the circulation, identify the source of TF+ microvesicles origin, and assess their effect on intravascular coagulation and inflammation. Approach and Results: C57BL/6J mice were administered with HNE intraperitoneally, and the release of TF+ microvesicles into circulation was evaluated using coagulation assays and nanoparticle tracking analysis. Various cell-specific markers were used to identify the cellular source of TF+ microvesicles. Vascular permeability was analyzed by the extravasation of Evans blue dye or fluorescein dextran. HNE administration to mice markedly increased the levels of TF+ microvesicles and thrombin generation in the circulation. HNE administration also increased the number of neutrophils in the lungs and elevated the levels of inflammatory cytokines in plasma. Administration of an anti-TF antibody blocked not only HNE-induced thrombin generation but also HNE-induced inflammation. Confocal microscopy and immunoblotting studies showed that HNE does not induce TF expression either in vascular endothelium or circulating monocytes. Microvesicles harvested from HNE-administered mice stained positively with CD248 and α-smooth muscle actin, the markers that are specific to perivascular cells. HNE was found to destabilize endothelial cell barrier integrity. HNE promotes the release of TF+ microvesicles from perivascular cells into the circulation. HNE-induced increased TF activity contributes to intravascular coagulation and inflammation.

Enhancement of ozonation of seawater-based wastewater containing pharmaceutical compounds by total residual oxidants: Salinity, ammonia, and organic matter

The ozonation process has recently been proposed as an effective treatment method for removing pharmaceutical compounds from seawater-based wastewater discharged from fish farms or hatcheries. Seawater ozonation can lead to the production of secondary stable oxidants such as bromine (HOBr/OBr−), which can be expressed as a total residual oxidants (TRO) owing to the high reaction rate constant with respect to ozone and bromide ion. TRO formation depends on water quality, in terms of aspects such as salinity, ammonia, and organic matter content; therefore, it is important to understand the variations in the ozone chemistry of bromide-containing water by considering the factors influencing TRO formation. In addition, the removal of pharmaceutical compounds in bromide-containing water should be evaluated owing to the different oxidation efficiency between TRO and pure aqueous ozone. This study aims to investigate the factors influencing the formation of TRO and the removal of pharmaceutical compounds during the ozonation of bromide-containing water. The results show that salinity increased the TRO formation rate by 6%, while ammonia and organic matter decreased the TRO formation rate by 51% and 39%, respectively. The removal efficiency of pharmaceutical compounds by TRO was higher compared with that by only ozone. Ammonia and organic matter inhibited the ozonation of bromide-containing water. These results indicate that TRO can be broadly used in the field of seawater ozonation; however, additional case studies on the removal of pharmaceutical compounds from seawater-based wastewater are needed to elucidate the oxidation mechanisms of various TRO.

Understanding of the Oxidation Behavior of Benzyl Alcohol by Peroxymonosulfate via Carbon Nanotubes Activation

Selective oxidation of benzyl alcohol (BzOH) into benzaldehyde (BzH) is very important in synthetic chemistry. Peroxymonosulfate (PMS) is a cheap, stable, and soluble solid oxidant, holding promise...

Plasmonic Zr-based metal-organic frameworks for accelerated de-colorization of methylene blue under LED light irradiation

Well-defined photocatalyst with 3D morphologies have attracted the attention of scientists due to the more accessible reactive surfaces, easy to recover from reaction medium, and low aggregation. Within this scope, photocatalysis based on plasmonic metal-organic frameworks (MOFs) were synthesized and utilized as an alternative reactive platform for visible-light degradation of methylene blue (MB) under green LED irradiation for the first time. In order to reduce the recombination between electron-hole pairs, a stable oxidant, namely sodium persulfate (PS) was employed to accelerate the photocatalytic decolorization of MB. These feasible strategies demonstrated that a bleaching degree of 91% (i.e., in the presence of PS) within 120 min was achieved compared to the bare Au@UiO-66@Pdop NPs (bleaching degree 31%). The obtained results from this study highlighted the superior properties of the newly synthesized core-shell Au@UiO-66@Pdop photocatalysts and clearly declared the great potential of the photo-responsive MOFs for organic pollutant degradations as well.

Oxone®-mediated direct arylselenylation of imidazo[2,1-b]thiazoles, imidazo[1,2-a]pyridines and 1H-pyrazoles

Oxone mediated reaction of imidazo[2,1-b]thiazole, imidazo[1,2-a]pyridine and 1H-pyrazole derivatives with diaryl diselenides is presented here. The methodology represents an efficient and simple protocol for carrying out the selective synthesis of 5-arylselanyl-imidazo[2,1-b]thiazoles, 3-arylselanyl-imidazo[1,2-a]pyridines and 4-arylselanyl-1H-pyrazoles in high yields using a stable, nontoxic and cheap oxidant. The reactions were conducted at 60 °C in air using acetonitrile as solvent. Alternatively, the use of ultrasound irradiation is presented as a tool for fast and efficient energy transfer that significantly reduced the reaction time.

A chemically regenerative redox fuel cell using (2,2,6,6-tetramethylpiperidin-1-yl)oxyl redox reaction in acid medium

(2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO) with no free radical and non-volatile characteristic can be utilized as a liquid catalyst instead of O2 at the cathode in a chemical regenerative redox fuel cell with H2 as a fuel at the anode. In this study, the electrochemical properties and performance of TEMPO dissolved in sulfuric acid solution are investigated using half and unit cells. In the half-cell, TEMPO shows an activation energy of 1.27 kcal mol−1 K−1 for the reduction. A chemical regenerative redox fuel cell (CRRFC) using TEMPO as the liquid catalyst exhibits an open circuit voltage of 0.7 V and a maximum power density of 90 mW cm−2 at 30 °C with a low activation loss. The regeneration cycling test of the CRRFC is performed at a constant voltage of 0.4 V under a flow rate of the oxygen-bubbled TEMPO solution. The performance of the CRRFC deteriorates, i.e., a power density of zero measured at >200 min. Thus, a highly efficient regeneration system needs to be developed for a high-performance CRRFC using TEMPO used as a liquid-type oxidant. Furthermore, stable liquid oxidants with relatively high standard reduction potentials can be proposed through various organic compounds.

Evidence for a Di-μ-oxo Diamond Core in the Mn(IV)/Fe(IV) Activation Intermediate of Ribonucleotide Reductase from Chlamydia trachomatis.

High-valent iron and manganese complexes effect some of the most challenging biochemical reactions known, including hydrocarbon and water oxidations associated with the global carbon cycle and oxygenic photosynthesis, respectively. Their extreme reactivity presents an impediment to structural characterization, but their biological importance and potential chemical utility have, nevertheless, motivated extensive efforts toward that end. Several such intermediates accumulate during activation of class I ribonucleotide reductase (RNR) β subunits, which self-assemble dimetal cofactors with stable one-electron oxidants that serve to initiate the enzyme's free-radical mechanism. In the class I-c β subunit from Chlamydia trachomatis, a heterodinuclear Mn(II)/Fe(II) complex reacts with dioxygen to form a Mn(IV)/Fe(IV) intermediate, which undergoes reduction of the iron site to produce the active Mn(IV)/Fe(III) cofactor. Herein, we assess the structure of the Mn(IV)/Fe(IV) activation intermediate using Fe- and Mn-edge extended X-ray absorption fine structure (EXAFS) analysis and multifrequency pulse electron paramagnetic resonance (EPR) spectroscopy. The EXAFS results reveal a metal-metal vector of 2.74-2.75 Å and an intense light-atom (C/N/O) scattering interaction 1.8 Å from the Fe. Pulse EPR data reveal an exchangeable deuterium hyperfine coupling of strength |T| = 0.7 MHz, but no stronger couplings. The results suggest that the intermediate possesses a di-μ-oxo diamond core structure with a terminal hydroxide ligand to the Mn(IV).

TcI Isolates of Trypanosoma cruzi Exploit the Antioxidant Network for Enhanced Intracellular Survival in Macrophages and Virulence in Mice.

Trypanosoma cruzi species is categorized into six discrete typing units (TcI to TcVI) of which TcI is most abundantly noted in the sylvatic transmission cycle and considered the major cause of human disease. In our study, the TcI strains Colombiana (COL), SylvioX10/4 (SYL), and a cultured clone (TCC) exhibited different biological behavior in a murine model, ranging from high parasitemia and symptomatic cardiomyopathy (SYL), mild parasitemia and high tissue tropism (COL), to no pathogenicity (TCC). Proteomic profiling of the insect (epimastigote) and infective (trypomastigote) forms by two-dimensional gel electrophoresis/matrix-assisted laser desorption ionization-time of flight mass spectrometry, followed by functional annotation of the differential proteome data sets (≥2-fold change, P < 0.05), showed that several proteins involved in (i) cytoskeletal assembly and remodeling, essential for flagellar wave frequency and amplitude and forward motility of the parasite, and (ii) the parasite-specific antioxidant network were enhanced in COL and SYL (versus TCC) trypomastigotes. Western blotting confirmed the enhanced protein levels of cytosolic and mitochondrial tryparedoxin peroxidases and their substrate (tryparedoxin) and iron superoxide dismutase in COL and SYL (versus TCC) trypomastigotes. Further, COL and SYL (but not TCC) were resistant to exogenous treatment with stable oxidants (H2O2 and peroxynitrite [ONOO(-)]) and dampened the intracellular superoxide and nitric oxide response in macrophages, and thus these isolates escaped from macrophages. Our findings suggest that protein expression conducive to increase in motility and control of macrophage-derived free radicals provides survival and persistence benefits to TcI isolates of T. cruzi.

ChemInform Abstract: 2‐Hydroxylation of 1,3‐Diketones with Atmospheric Oxygen.

An efficient method for the 2-hydroxylation of 1,3-diketones by using atmospheric oxygen as an oxidant under transition-metal-free condition is described. The protocol has the advantages of using an inexpensive and stable oxidant, producing high yields, and requiring ecofriendly conditions.

Quantitative generation of cation radicals and dications using aromatic oxidants: effect of added electrolyte on the redox potentials of aromatic electron donors

Redox titrations using robust aromatic oxidants allow for a quantitative analysis of redox and optical properties of organic electron donors in their oxidized states. Unlike spectroelectrochemistry, redox titrations can be performed without added electrolyte in relatively nonpolar solvents, affording quick access to the redox and optical properties of a given electron donor without the need of a complex electrochemical setup. However, the redox potentials obtained by the two methods are not the same. To establish the direction and magnitude of this discrepancy, we have performed a systematic case study using a set of tetraarylethylene donors and a tetrasubstituted hydroquinone ether cation radical (THEO+•) as a stable aromatic oxidant. We show that redox potentials (especially second and higher oxidation potentials) measured by electrochemical methods are systematically lower compared with the redox potentials obtained by redox titrations in the absence of electrolyte, because of the enhanced stabilization of dications and polycations by electrolyte. We have also uncovered that the smaller cation radicals (e.g., a para‐hydroquinone or ortho‐hydroquinone ether cation radicals) are much more effectively stabilized when compared with the cation radicals in which charge is delocalized over larger area (e.g., tetraarylethylene cation radicals) in the presence of electrolyte because of increased ionic strength of the solution. Copyright © 2015 John Wiley &amp; Sons, Ltd.

2-Hydroxylation of 1,3-Diketones with Atmospheric Oxygen

An efficient method for the 2-hydroxylation of 1,3-diketones by using atmospheric oxygen as an oxidant under transition-metal-free condition is described. The protocol has the advantages of using an inexpensive and stable oxidant, producing high yields, and requiring ecofriendly conditions.

ChemInform Abstract: Oxidation Reactions Using Polymer‐Supported 2‐Benzenesulfonyl‐3‐(4‐nitrophenyl)oxaziridine.

A thermally stable polymer-supported oxidant has been developed. Polymer-supported 2-benzenesulfonyl-3-(4-nitrophenyl)oxaziridine was applied to microwave-assisted reactions that occurred at high temperatures and was shown to oxidize alkenes, silyl enol ethers, and pyridines to the corresponding epoxides and pyridine N-oxides in excellent to good yields and with much shorter reaction times. It also enabled tetrahydrobenzimidazoles to be oxidatively rearranged to spiro fused 5-imidazolones in a more efficient manner. Recycling of the polymer-supported oxidant is also possible with minimal loss of activity after several reoxidations.