Radical Formation Research Articles

Mechanism of Sulfate Radical Formation on Activation of Persulfate Using Doped Metal Oxide and Its Role in Degradation of Tartrazine Dye in an Aqueous Solution.

Degradation of tartrazine dye (TZD) was performed in this study using sulfate radicals (SO4•-) generated from the activated sodium persulfate (SPS) using Fe3O4@PDA nanoparticles (NPs). The NPs were characterized by Fourier transform infrared (FTIR), vibrating sample magnetometer (VSM), X-ray diffraction (XRD), high-resolution scanning electron microscopy (HR-SEM), X-ray photoelectron spectroscopy (XPS), high resolution transmission electron microscopy (HRTEM), and energy-dispersive X-ray spectroscopy (EDX). The average particle size of the NPs was 17.49 nm from XRD analysis. The presence of the C-N group at 1129 cm-1 in FTIR and 2.54% of the nitrogen element identified from the EDX plot was evidence of successful doping of polydopamine (PDA). Superparamagnetic nature with a decrease in the Ms value to 42.015 emu/g after doping was determined. Doping was further confirmed by XPS analysis with binding energies at 399.68 and 400.99 eV. The average particle size from HRTEM analysis was 21.47 nm with a lattice spacing of 0.30 nm. Turnover number (TON) and turnover frequency (TOF) values for Fe3O4@PDA were determined to be 3.72 and 0.0248 min-1 with respect to different systems, respectively. Optimum conditions for the Fe3O4@PDA/SPS system were 50 ppm TZD, 0.9 g/L catalyst, 12 mM SPS, and pH 4 with 94.68% efficiency in 150 min. The inhibition effect of ions in TZD degradation followed the order humic acid <NO3- < Cl- < CO32. The kinetic model fitting the Fe3O4@PDA/SPS system has pseudo-second-order kinetics. Excess formation of SO4•- produced hydroxyl radicals (•OH) that were identified by a scavenging test. Reusability of the NPs was performed for five cycles and showed acceptable degradation performance up to 82.47%. The intermediates identified from gas chromatography-mass spectrometry (GCMS) proved the cleavage of azo and sulfonate groups of TZD with the formation of nontoxic intermediates. Finally, the phytotoxicity assessment was studied using Vigna radiata (Green grams). The % decrease of the root, shoot, and seedling length for the degraded dye solution was negligible. Hence, this study proved that the Fe3O4@PDA/SPS system could effectively degrade TZD with nontoxic intermediate formation.

Biaryl Anion Radical Formation by Potassium Metal Reduction of Aryl Isocyanates and Triaryl Isocyanurates.

The potassium metal reduction of aryl isocyanates (aryl = phenyl, p-tolyl, 3,5-dimethylphenyl, 4-biphenylyl, and 1-naphthyl) in THF with 18-crown-6 or in HMPA results in the formation of the corresponding triaryl isocyanurate anion radicals. Continued exposure to potassium results in loss of the isocyanurate anion radical and the eventual formation of the respective biaryl anion radical. The 1,1'-binaphthyl anion radical is found to undergo a cyclodehydrogenation reaction, which leads to formation of the perylene anion radical. When authentic triaryl isocyanurates are reduced with metal, the heterocyclic ring undergoes fragmentation with elimination of carbon monoxide to produce a triarylbiuret dianion. This ring opening reaction is initiated by the two-electron reduction of the neutral isocyanurate species. The biaryl anion radical is formed when the biuret dianion is reduced further with metal. A possible mechanism for biaryl formation involves a heterolytic cleavage of an aryl C-N bond and release of an aryl radical once the triarylbiuret dianion is further reduced. A subsequent intermolecular reaction between two aryl radicals forms the corresponding biaryl, which can then be reduced to the anion radical. Notably, when a mixture of two different triaryl isocyanurate compounds is reduced in solution, the corresponding mixed biaryl anion radical is generated.

Oxoammonium salts exert antiviral effects against coronavirus via denaturation of their spike proteins

Severe acute respiratory syndrome-coronavirus-2 (SARS-CoV2) infection has forced social changes worldwide. Development of potent antiviral agents is necessary to prevent future pandemics. Titanium oxide, a photocatalyst, is a long-acting antiviral agent; however, its effects are weakened in the dark. Therefore, new antiviral substances that can be used in the dark are needed. Two types of nitroxyl radicals, 2,2,6,6-tetramethylpiperidine N-oxyl (TEMPO) and 2-azaadamantane N-oxyl (AZADO), are commonly used as oxidation catalysts utilizing oxygen in the air as the terminal oxidant. Therefore, in this study, we aimed to evaluate the potential of these radicals as antiviral compounds with sustained activity even in the dark. We evaluated the antiviral effects of oxoammonium salts corresponding to TEMPO and AZADO (TEMPO-Oxo and AZADO-Oxo, respectively), which are the active forms of nitroxyl radicals in oxidation reactions. TEMPO-Oxo and AZADO-Oxo inhibited the binding of SARS-CoV2 spike protein receptor-binding domain (S-RBD) to angiotensin-converting enzyme 2. Notably, AZADO-Oxo exhibited a 10-fold stronger inhibitory effect than TEMPO-Oxo. TEMPO-Oxo and AZADO-Oxo also denatured S-RBD; however, effects of AZADO-Oxo were 10-fold stronger than those of TEMPO-Oxo and did not change in the dark. Some S-RBD peptides treated with AZADO-Oxo were cleaved at the N-terminal side of tyrosine residues. TEMPO-Oxo and AZADO-Oxo exhibited concentration-dependent antiviral effects against feline coronavirus. In conclusion, active forms of the nitroxyl radicals, TEMPO-Oxo and AZADO-Oxo, exerted antiviral effects by denaturing S-RBD, regardless of the presence or absence of light, suggesting their potential as novel antiviral agents.

Modeling Analysis of Nocturnal Nitrate Formation Pathways during Co-Occurrence of Ozone and PM2.5 Pollution in North China Plain

The rapid formation of secondary nitrate (NO3−) contributes significantly to the nocturnal increase of PM2.5 and has been shown to be a critical factor for aerosol pollution in the North China Plain (NCP) region in summer. To explore the nocturnal NO3− formation pathways and the influence of ozone (O3) on NO3− production, the WRF-CMAQ model was utilized to simulate O3 and PM2.5 co-pollution events in the NCP region. The simulation results demonstrated that heterogeneous hydrolysis of dinitrogen pentoxide (N2O5) accounts for 60% to 67% of NO3− production at night (22:00 to 05:00) and is the main source of nocturnal NO3−. O3 enhances the formation of NO3 radicals, thereby further promoting nocturnal N2O5 production. In the evening (20:00 to 21:00), O3 sustains the formation of hydroxyl (OH) radicals, resulting in the reaction between OH radicals and nitrogen dioxide (NO2), which accounts for 48% to 64% of NO3− formation. Our results suggest that effective control of O3 pollution in NCP can also reduce NO3− formation at night.

Nitrogen‐Induced Microcrystalline‐to‐Nanocrystalline Structure Transition in Diamond Films Grown by Microwave Plasma Chemical Vapor Deposition: Comparison of N2 and NH3 Precursors

The structure and properties of polycrystalline chemical vapor deposition (CVD) diamond coatings grown by microwave plasma CVD in H2–CH4 mixtures can be effectively controlled by nitrogen admixture in the process gas. Here, a comparative study of adding nitrogen from different precursors, N2 and ammonia NH3, in concentrations up to 0.4%vol on grain size, texture, surface roughness, and sp2/sp3 ratio of the produced films on Si substrates is performed. A transition from microcrystalline to smooth nanocrystalline diamond structure is found to occur at a certain concentration of the precursor, for NH3 this threshold concentration being much lower, 0.02–0.1%, than for N2. The higher activity of ammonia is associated with easier formation of cyano radicals in the plasma as detected with optical emission spectroscopy, in accord with the lower bond‐dissociation energy for NH3 compared to N2. On the contrary, a smaller addition (0.004%) of either N2 or NH3 promotes almost doubling of the growth rate, while preserving the microcrystalline structure of the film. The results establish ammonia as a convenient alternative precursor to commonly used N2 added in the plasma for the diamond film structure modifications.

UV photochemistry of the L-cystine disulfide bridge in aqueous solution investigated by femtosecond X-ray absorption spectroscopy

The photolysis of disulfide bonds is implicated in denaturation of proteins exposed to ultraviolet light. Despite this biological relevance in stabilizing the structure of many proteins, the mechanisms of disulfide photolysis are still contested after decades of research. Herein, we report new insight into the photochemistry of L-cystine in aqueous solution by femtosecond X-ray absorption spectroscopy at the sulfur K-edge. We observe homolytic bond cleavage upon ultraviolet irradiation and the formation of thiyl radicals as the single primary photoproduct. Ultrafast thiyl decay due to geminate recombination proceeds at a quantum yield of >80 % within 20 ps. These dynamics coincide with the emergence of a secondary product, attributed to the generation of perthiyl radicals. From these findings, we suggest a mechanism of perthiyl radical generation from a vibrationally excited parent molecule that asymmetrically fragments along a carbon-sulfur bond. Our results point toward a dynamic photostability of the disulfide bridge in condensed-phase.

Physicochemical, Textural, and Antioxidant Attributes of Yogurts Supplemented with Black Chokeberry: Fruit, Juice, and Pomace.

The fruit, juice, and pomace of black chokeberry (Aronia melanocarpa) are a rich source of phenolic compounds and can be used to obtain enriched dairy products. Chokeberry fruit, due to its astringent taste, is less favorable or even unacceptable to consumers and is usually processed into juice, resulting in large quantities of pomace, which is often discarded as waste. The aim of this study is to valorize chokeberry fruit, juice, and pomace by incorporating them in different percentages (1, 2, and 3%) into yogurt as functional ingredients. The physicochemical (total solids content, fat, protein, titratable acidity, pH, color), textural (hardness, adhesion, cohesiveness, springiness, gumminess, and chewiness), antioxidant (DPPH scavenging activity and total phenolic content), and sensory characteristics of supplemented yogurts were investigated. The results showed that the addition of chokeberry pomace in yogurt increased their total solids content (from 11.46 ± 0.18% for the plain yogurt sample to 13.71 ± 0.18% for the yogurt sample with 3% chokeberry pomace), while the addition of fruit and juice decreased the protein content of the yogurt samples (from 4.35 ± 0.11% for the plain yogurt sample to 3.69 ± 0.15% for the yogurt sample with 3% chokeberry fruit and to 3.84 ± 0.1% for the yogurt sample with 3% chokeberry juice). There was no statistically significant change in the fat content of all samples of chokeberry-supplemented yogurt compared to plain yogurt. The pH of the yogurt samples decreased with the increase in the percentage of chokeberry fruit, juice, and pomace added to the yogurt (from 4.50 for the plain yogurt samples to 4.35, 4.30, and 4.20 for the yogurt samples supplemented with 1, 2, and 3% black chokeberry pomace). Inhibition of DPPH radical formation was higher in the yogurt samples with chokeberry fruit (57.84 ± 0.05%, 73.57 ± 0.11%, and 75.38 ± 0.05% inhibition for the samples with 1, 2, and 3% fruit) and pomace (up to 64.8 ± 0.11% inhibition for the sample with 3%), while total phenolic content decreased (from 392.14 ± 2.06 to 104.45 ± 2.63 µg/g) as follows: yogurt with chokeberry pomace > yogurt with chokeberry fruit > yogurt with chokeberry juice. The yogurt samples with the highest acceptance scores were the samples with 3% and 2% black chokeberry fruit, while the lowest acceptance score was obtained for the yogurt sample with 3% black chokeberry pomace. Chokeberry fruit, juice, and pomace can improve the physicochemical, textural, and antioxidant characteristics of yogurt, emphasizing that the antioxidant effect of yogurt could be substantially improved by the addition of chokeberry pomace due to its high phenolic content, while incorporation into yogurt is another way to valorize this by-product.

Gamma irradiation-induced degradation of hexachlorobenzene in methanol: Kinetics, mechanism and dehalogenation pathway

Hexachlorobenzene (HCB), a persistent organic pollutant (POP) and organochlorine compound (OCC), poses significant environmental and health risks due to its high stability and solubility in fats, oils, and organic solvents. This study investigates the degradation of HCB in methanol using gamma irradiation with a60Co source. A 2 × 10−4 M solution of HCB in methanol was prepared and irradiated at a dose rate of 1.74 Gy/s. The degradation process was monitored using Gas Chromatography-Mass Spectrometry (GC-MS), with optimized parameters for effective separation and analysis of byproducts.The results demonstrated a 100% degradation of HCB at an absorbed dose of approximately 51 kGy. The degradation pathway involved successive dechlorination, forming various chlorinated benzene (CB) byproducts such as pentachlorobenzene (PCB), tetrachlorobenzenes (TeCB), trichlorobenzenes (TCB), dichlorobenzenes (DCB), and ultimately benzene.Ion chromatography (IC) analysis revealed a dose-dependent increase in Cl⁻ concentrations, confirming the efficiency of dechlorination. A chlorine mass balance was performed to evaluate the distribution of chlorine during the degradation process, tracking Cl⁻ ions, CBs, and residual HCB. As the dose increases, the chlorine content in residual HCB decreases significantly, with none remaining at 50.2 kGy and beyond. At 169.5 kGy, nearly all chlorine (99.96%) is unaccounted for, suggesting that it has likely been released as gaseous byproducts, such as Cl₂ or other volatile chlorinated compounds.The formation of solvated electrons and hydrogen radicals initiated the dechlorination process, as evidenced by the identified reaction mechanisms. Kinetic analysis indicated that the degradation followed pseudo-first-order kinetics, with a rate constant of 5 × 10−4 s−1. The study also outlines a dose-dependent trend in radiation chemical yields (G values), initially increasing to a peak of 7.3 × 10−2 molecules per 100 eV at 12.6 kGy and subsequently decreasing to as low as 5.4 × 10−4 at 50.2 kGy.This study highlights the effectiveness of gamma irradiation for the complete degradation of HCB in methanol, offering a promising method for the remediation of POPs-contaminated environments. The proposed mechanism and kinetic properties provide a comprehensive understanding of the radiolytic degradation process, paving the way for further applications in environmental cleanup technologies.

Biodegradation of organic micropollutants by anoxic denitrification: Roles of extracellular polymeric substance adsorption, enzyme catalysis, and reactive oxygen species oxidation

The control of organic micropollutants (OMPs) in water environments have received significant attention. Denitrification was reported to exhibit good efficiency to remove OMPs, and the mechanisms involved in are too intricate to be well illustrated. In this study, we selected nitrobenzene [NB] and bisphenol A [BPA] as model pollutants and aimed to unravel the mechanisms of Paracoccus Denitrificans in the removal of OMPs, with a specific emphasis on aerobic behavior during denitrification processes. We demonstrated the formation of extracellular superoxide radicals, i.e., extracellular •O2-, using a chemiluminescence probe and found that extracellular polymeric substance adsorption, extracellular •O2-, and microbial assimilation contributed approximately 40 %, 10 %, and 50 % to OMPs removal, respectively. Transcriptome analysis further revealed the high expression and enrichment of several pathways, such as drug metabolism-other enzymes, of which a typical aerobic enzyme of polyphenol oxidase [PPO] participates in the degradation of NB and BPA. Importantly, all the immediate products showed a significant decrease in toxicity during the aerobic activity-related OMPs degradation process based on the proposed degradation pathways. This study demonstrates the formation of extracellular •O2- and the mechanisms of extracellular •O2-- and PPO-mediated OMPs biodegradation, and offers new insights into OMPs control in widely-used denitrification treatment processes.

Ultraviolet/dielectric barrier discharge enhanced ultrafiltration for treating natural water: Performance, mechanism and iodinated disinfection by-product fate

This study employed ultraviolet (UV)/ dielectric barrier discharge (DBD) pre-treatment to mitigate ultrafiltration membrane fouling and enhance the purification efficiency of natural surface water. Moreover, as an emerging contaminant, the iodinated disinfection by-products’ fate and degradation performance were discussed. The investigation revealed that the generation of numerous active species (⋅OH, ⋅O2−, 1O2, etc) under high input voltage and low pH conditions were advantageous for augmenting membrane flux, with sodium sulfate electrolyte playing a role in promoting the formation of selective sulfate radicals. Fluorescence excitation-emission matrix spectroscopy indicated that the UV/DBD system at 5.5 kV can effectively degrade proteins and humic substances in surface water, leading to an enhancement in water quality. With the assistance of UV radiation, macromolecular organic matter underwent extensive decomposition into smaller molecules, thus creating an ideal environment for controlling membrane fouling in the UV/DBD system. Additionally, it was identified the intermediate products and degradation pathways during iopamidol degradation by UV/DBD. It also affirmed the minimal risk of disinfection by-product generation with this strategy. The study provides a viable and efficient pre-treatment approach for mitigating membrane fouling and purifying water.

Light-Driven N-Heterocyclic Carbene-Catalyzed Multi-Component Reaction for the Synthesis of β-Amino Ketones.

A N-heterocyclic carbene-catalyzed (NHC) three-component reaction involving N-aminopyridinium salts, alkenes, and aldehydes for the synthesis of β-amino ketones is described. In this reaction, N-aminopyridinium salts and the Breslow intermediate, which is generated from NHC and aldehydes, are utilized to undergo a single-electron transfer process, forming a ketyl radical intermediate and amidyl radicals. Subsequent to the formation of the amidyl radical, it undergoes selective capture by alkenes, followed by radical cross-coupling to yield the desired β-amino ketones.

Electron Paramagnetic Resonance Analysis of Hydroquinone Polymerization Catalyzed by Small Laccase

AbstractLaccases are multi‐copper oxidases (MCOs) that oxidize a broad range of substrates while reducing molecular oxygen to water. Although much effort has been made to elucidate the catalytic mechanism of laccases, information about reactive catalytic intermediates during catalysis is not yet fully understood. Herein, hydroquinone (HQ) polymerization catalyzed by prokaryotic small laccase (SLAC) was investigated by electron paramagnetic resonance (EPR) spectroscopy to provide more information on the catalytic mechanism. Briefly, free radical intermediates during the catalysis were investigated by real‐time in situ EPR measurement to monitor the formation and transformation of free radicals. A paramagnetic species was identified which was attributed to a copolymer formed by hydroquinone, benzoquinone, and semiquinone radical. In addition, the low‐temperature EPR spectrum of the trinuclear copper center during catalysis not only revealed tentative rotational motion of the histidine imidazole rings coordinating the TNC upon electron uptake but also provided evidence of the formation of oxygen bridge at TNC during the reaction, represented by the observation of a new type 2 copper component featured larger g// values and smaller A// values. Together, EPR spectroscopic insights into the catalytic intermediates during enzymatic hydroquinone polymerization have extended the knowledge of the biophysical characteristics and catalytic mechanism of SLAC.

Organophotocatalytic Selective Deuteration of Metabolically Labile Heteroatom Adjacent C-H Bonds via H/D Exchange with D2O.

We report a general approach for efficient deuteration of the metabolically labile α-C-H bonds of widespread amides and amines. Temporarily masking the secondary amine group as a carbamate allows an unprecedented photoredox hydrogen atom transfer-promoted α-carbamyl radical formation for efficient H/D exchange with D2O. The mild protocol delivers structurally diverse α-deuterated secondary amines including "privileged" piperidine and piperazine structures highly regioselectively with excellent levels of deuterium incorporation (≤100%). Furthermore, we successfully implemented the strategy for α-deuteration of amides, lactams, and ureas with high regioselectivity and high levels of D incorporation. Finally, the observed efficient deuteration of secondary alcohol moieties in late-stage modification of complex amine-containing pharmaceuticals allows for the development of a viable method for efficient α-deuteration of the important functionality.

Exploring the catalytic conversion of aromatic model compounds of coal pyrolysis over Ca(OH)2

The distribution of pyrolysis products from aromatic model compounds in coal catalyzed by Ca(OH)2 was investigated at the molecular level. The composition and relative abundance of the pyrolysis products from coal were analyzed using Py-GC/MS. The rapid pyrolysis products of coal at 600 °C consisted of phenols (15.94 %), non-phenolic oxygenated compounds (25.31 %), aliphatics (49.03 %), aromatic compounds (21.74 %), and other compounds (0.03 %). Six representative aromatic model compounds (2-methoxy-4-methylphenol, p-cresol, 2,4-dimethylphenol, o-cresol, guaiacol, and catechol) were selected. The pyrolysis process of model compounds was primarily the cleavage of C-O and C-C bonds, which resulted in the formation of methoxy and methyl radicals. The results revealed that Ca(OH)2 undergoes acid-base reactions with -OH, thereby increasing the stability of the model compounds. Notably, the impact of Ca(OH)2 on the composition and distribution of pyrolysis products was significantly more pronounced in aromatic compounds containing both -OCH3 and -OH compared to those containing solely -OH. The formation pathways of pyrolysis products involving guaiacol and Ca(OH)2 were elucidated through density functional theory (DFT) calculations, demonstrating that Ca(OH)2 could facilitate more free radicals release and the conversion of model compounds. This study contributes to the understanding of the transformation of aromatic compounds during coal pyrolysis at the molecular level.

Salafism, neo-salafism, and post-salafism. Evolutions of a radical current of Islam in France

ABSTRACT The issue of Salafism has become central to public debate in France today. While the Salafi movement in France has been portrayed in politics and media alike as a major security threat opposed to republican principles, its sociology reveals more complex patterns than one of radicalism alone, especially from a long-term perspective. An empirical analysis of discourses, behaviours and mobilization strategies within these puritanical fundamentalist communities leads us to hypothesize that since the early 2000s, the radicalism initially displayed by Salafism has proved unsustainable. Through looking at the long-term life trajectories of Salafi believers, we propose an overview of the different biographic scenarios that characterize these actors. What can we say about the way in which they have reinforced, reformulated, nuanced, or broken their ties with their Salafi socialisation? We show that Salafism in France today can be characterized as a fundamentalism diluted by a broader global dynamic of distrust towards violence and classic forms of political militancy, while at the same time maintaining claims to certain forms of religious radicalism. Based on a micro-sociological approach, we examine whether the respective prefixes ‘neo’ or ‘post’ most accurately characterize the long-term evolution of French Salafism.

Dose-dependent effect of cadaverine on hydroxyl radicals’ production by human peripheral blood leukocytes

Objective. To assess changes in the generation of hydroxyl radicals by leukocytes under the influence of cadaverine at concentrations of 1, 5 and 25 mmol/L. Materials and methods. Peripheral venous blood samples were obtained from 40 apparently healthy donors. To assess the production of hydroxyl radicals, a luminol-dependent chemiluminescence reaction with blood leukocytes, which were pre-incubated with cadaverine at concentrations of 1, 5 and 25 mmol/L was carried out. The study was conducted on a Luminoskan Ascent® Thermo Labsystems (USA) luminometer for 180 minutes. For statistical analysis, the integral chemiluminescence indicator for the entire measurement period (RLU) was used. The time to reach the maximum of light flashes in minutes, the intensity of the utmost glow, and the area under the luminescence extinction curve were calculated. Results. It was determined that pre-incubation of cells with cadaverine significantly reduces their time to reach the maximum generation of hydroxyl radicals. In addition, cadaverine enhances the intensity of the reaction of luminol-dependent chemiluminescence of leukocytes of healthy donors, and the greatest stimulating effect was recorded at a polyamine concentration of 5 mmol/L (p =0,009 to samples with a spontaneous reaction, p =0,007 and 0,010 to samples with cadaverine 1 mmol/L and 5 mmol/L respectively). Cadaverine increases the area under the reaction curve, it being the most significant at a concentration of 5 mmol/L – 20.89±3.00 c.u. versus 0.86±0.07 c.u. with a spontaneous reaction (p=0,001). Conclusions. The results of the study indicate a possible effect of cadaverine on the mechanisms of hydroxyl radical formation, as well as the activity of the diamine oxidase enzyme in leukocytes. It can be supposed that the combination of these effects contributes to the development of the environment favorable for microorganisms at the focus of inflammation. Thus, microorganisms that produce cadaverine, which modulates the generation of hydroxyl radicals by leukocytes, adapt to their environment, creating a special type of microenvironment, which probably results in an asymptomatic course of the inflammatory process.

The Interaction of Myeloperoxidase with the Industrial Contaminant 6-PPD: A Potential Pathway for Reactive Metabolites.

6-PPD (N-[1,3-dimethylbutyl]-N'-phenyl-p-phenylenediamine) is an industrial antioxidant reported to be an environmental contaminant. It was found to be highly toxic to coho salmon and potentially other aquatic organisms. The toxicity of 6-PPD in humans, however, remains unknown. The neutrophil enzyme myeloperoxidase (MPO) is known to catalyze xenobiotic metabolism; therefore, its role in 6-PPD cytotoxicity was investigated using the MPO-rich HL-60 cell line. UV-visible spectroscopy and liquid chromatography-mass spectrometry (LC/MS) were performed to investigate the MPO-mediated oxidation of 6-PPD and identify possible metabolites in the absence and presence of glutathione (GSH). 6-PPD's cytotoxicity, effect on mitochondrial membrane potential (MMP), and GSH-depleting ability in HL-60 cells were assessed. Electron paramagnetic resonance (EPR) was used to determine GSH radical formation using DMPO, and mitochondrial-derived superoxide was assessed with the mito-TEMPO-H probe. Evaluation of the 6-PPD-induced cellular injury pathways was performed by preincubating an antioxidant and an MPO inhibitor with HL-60 cells. UV-vis analysis of MPO-catalyzed oxidation of 6-PPD demonstrated changes in the 6-PPD spectrum, whereas the addition of GSH altered the spectrum, indicating possible GSH conjugate formation. LC/MS showed the formation of multiple products, including GSH-6-PPD conjugates and a GSH conjugate to a 4-hydroxydiphenylamine (a known 6-PPD degradant), which could potentially induce cytotoxicity. 6-PPD demonstrated concentration-dependent cytotoxicity, and cellular GSH levels were decreased by 6-PPD. Similarly, the level of MMP decreased, suggesting mitochondrial depolarization. Furthermore, the EPR spin probe for mitochondrial superoxide showed a positive relationship with 6-PPD concentration, and EPR spin-trapping demonstrated 6-PPD concentration-dependent GSH radical signal intensity using MPO/H2O2. The GSH precursor, NAC, demonstrated partial cytoprotection against 6-PPD; however, the MPO inhibitor PF-1355 surprisingly showed no significant cytoprotective effect. Our results suggest that MPO could be a potential catalyst for 6-PPD toxicity in humans. However, MPO inhibition did not significantly affect cellular viability, suggesting an MPO-independent toxicity pathway. These findings warrant a deeper investigation to determine 6-PPD mammalian toxicity pathways.

Three-component carbonylative Michael addition of aryl bromides using abundant metal-carbonyl under light

Carbonyl compounds are widely found in various chemical reactions and natural products. Herein, a light-driven carbonylative cross-coupling reaction of bromobenzene was reported. Co2(CO)8 was used as an abundant solid carbonyl source to synthesize various Michael addition products with high yields. This reaction has broad substrates scope with good functional group tolerance. The mechanism study indicated that the reaction is achieved by the formation of benzoyl radical from homolytic C–Co cleavage under irradiation.

Modification of activated carbon through chemical-physical activation method with KOH and 60Co gamma irradiation from banana leaf waste

Abstract Until now waste is still a problem in many big cities in Indonesia. In addition, the amount of waste increases as the population increases. Banana leaf waste is no exception, which is included in other types of waste, which accounts for 6.33% of the total waste in Indonesia in 2022. Utilization of banana leaf waste as a raw material for activated carbon production can also be an alternative to reducing the amount of wasted banana leaf waste because they contain various kinds of organic compounds. Activated carbon is widely used as an adsorbent in various sectors, especially in the industrial sector. Production of activated carbon must go through an activation process to enlarge the surface pores either chemically or physically, or even both. This study aims to compare the results of activated carbon surface area and functional groups using the chemical-physical activation method from banana leaf biomass raw materials with KOH and gamma irradiation at various doses. The research method used is an experimental method consisting of 4 stages: dehydration, carbonization, activation, and characterization. The research was started by dehydrating the leaves and continued with the carbonization stage at 350°C for 30 minutes. Carbon was divided into four samples that consisted of 1 blank and 3 test materials that activated with 30% (w/v) KOH solution for 24 hours and gamma-irradiated with a dose of 10, 30, and 50 kGy. Results were characterized using FTIR and BET. The effect of gamma 60Co irradiation on the activated carbon material from banana leaf waste can increase the peak transmittance value of the activated carbon functional group due to the formation and reaction of free radicals on its surface. Increase in the surface area (from 6.504 to 24.04 m2/g) is also associated with an increase in the absorbed dose due to the formation of more free radicals. However, the surface area obtained is not as expected due to the possibility of pore blockage and excessive activation time, which causes the surface area of the material to be small.

Formation of Hydroxyl Radicals in Advanced Oxidation Processes for the Degradation of Contaminated Organic Matter

Organic compounds in different solutions have caused several pollution problems to the environment and even affected human health. Advanced Oxidation Processes (AOPs) have been effectively used in the decontamination of these types of compounds. Distinct reactive oxygen species (ROS) have been proposed to explain the degradation or mineralization of contaminating organic matter. ROS, such as free radicals (e.g., .OH), superoxide (e.g., .O2 −), and peroxides (e.g., H2O2), are capable of modifying the chemical structure of organic matter and consequently degrade or mineralize it. In this review, the formation of hydroxyl radicals in each AOP, as in a hybrid process, and the methods for quantifying and determining this type of radical are discussed.