Oxidation Products Research Articles

6PPD, Not 6PPD-Quinone, Induced Serious Zebrafish Eye Damage by Disrupting the Thyroid Signaling Pathway.

N-(1,3-Dimethylbutyl)-N'-phenyl-1,4-phenylenediamine (6PPD) and its oxidation product 6PPD-quinone (6PPDQ) showed different acute toxicities and bioaccumulation potencies in fish. In this study, we compared the thyroid disrupting effects of 6PPD and 6PPDQ through in vitro, in silico, and in vivo assays. Interestingly, although 6PPD and 6PPDQ showed similar docking affinities with thyroid hormone receptor (TR) isoforms and GH3 cell inhibition effects, the thyroid signaling pathway, eye development, phototactic behaviors, and cell density in the retinal layer in the larval zebrafish were significantly affected only following 6PPD exposure. Further investigation demonstrates that 6PPD can act as a TR antagonist to reduce the opsin protein abundance and inhibit the cone photoreceptor cell proliferation, which finally alters the retinal layer structure and causes microphthalmus in zebrafish. Especially, under environmental relevant concentration exposure, 6PPD induced alterations of trβ, opn1lw1, opn1mw1, rpe65a, nr2e3 gene expressions although no significant eye histopathological change was observed. This study illustrates for the first time the more serious visual system impairment of 6PPD compared to 6PPDQ, with thyroid signaling disruption being a contributing factor, while other important toxic targets still require further research.

Isoprene nitrates drive new particle formation in Amazon’s upper troposphere

New particle formation (NPF) in the tropical upper troposphere is a globally important source of atmospheric aerosols1, 2, 3–4. It is known to occur over the Amazon basin, but the nucleation mechanism and chemical precursors have yet to be identified2. Here we present comprehensive in situ aircraft measurements showing that extremely low-volatile oxidation products of isoprene, particularly certain organonitrates, drive NPF in the Amazonian upper troposphere. The organonitrates originate from OH-initiated oxidation of isoprene from forest emissions in the presence of nitrogen oxides from lightning. Nucleation bursts start about 2 h after sunrise in the outflow of nocturnal deep convection, producing high aerosol concentrations of more than 50,000 particles cm−3. We report measurements of characteristic diurnal cycles of precursor gases and particles. Our observations show that the interplay between biogenic isoprene, deep tropical convection with associated lightning, oxidation photochemistry and the low ambient temperature uniquely promotes NPF. The particles grow over time, undergo long-range transport and descend through subsidence to the lower troposphere, in which they can serve as cloud condensation nuclei (CCN) that influence the Earth’s hydrological cycle, radiation budget and climate1,4, 5, 6, 7–8.

U-Pb ages of apatite, sulfur isotopes of sulfides and possible origin of the Dashui hematite-rich, sulfide-deficient gold deposit in the West Qinling orogen, Central China

The Dashui gold deposit is one of the largest Au deposits in West Qinling orogenic belt and unique for its hematite-rich and sulfide-rare Au mineralization. The age and genesis of the Dashui Au deposit, however, remain poorly constrained. To resolve these issues, here we present robust apatite U-Pb dating results under the context of detailed textural and compositional studies. The ore mineral assemblages at Dashui consist of fine-grained quartz, hematite, kaolinite, apatite, native Au, and trace amounts of pyrite. The presence of hematite and gold as inclusions fully enclosed in quartz and apatite suggests that the former minerals are of primary origin rather than, as generally considered, a product of supergene oxidation of Au-bearing pyrite. Cathodoluminescence imaging reveals that the ores contain two types of apatite. CL-bright apatite was likely inherited from the magmatic wall rocks, whereas CL-dark apatite precipitated coevally with the ore minerals. In-situ LA-ICP-MS U-Pb isotope analysis of the CL-dark apatite suggests that the Dashui deposit formed at 217.2 ± 4.1 Ma, contemporaneously with the main stage of regional Au mineralization in the West Qinling orogenic belt that formed under the Triassic subduction-collisional tectonic setting. Since the Dashui Au mineralization is temporarily and spatially associated with intermediate to felsic porphyry intrusions, and that the ore sulfides have S isotopes consistent with a magmatic-hydrothermal origin, the deposit can be broadly classified as a Carlin-type Au deposit. Nevertheless, the hematite-rich rather than pyrite-rich ore assemblages indicate an ore-forming environment that was more oxidized than that of typical Carlin-type deposits.

Unveiling the organic chemical composition and sources of organic carbon in PM2.5 at an urban site in Greater Cairo (Egypt): A comprehensive analysis of primary and secondary compounds

This work presents an exhaustive chemical characterization of the organic fraction of fine particulate matter (PM2.5) collected at an urban site in the Greater Cairo Area, Egypt, one of the most polluted megacities in the world. An intensive 2-month sampling campaign was conducted at an urban site in Giza (Dokki), from November 26, 2019, to January 28, 2020. Daily (24-h integrated) PM2.5 filter samples were then analyzed for their carbonaceous (OC, EC) and organic fractions including primary (n-alkanes, phthalates, fatty acids, polycyclic aromatic hydrocarbons, hopanes, sugars, and sugar alcohols) and secondary (isoprene and β-caryophyllene oxidation products, and dicarboxylic acids) compounds. Average organic (OC) and elemental carbon (EC) concentrations were 17.8 ± 6.6 μg/m3 and 4.4 ± 1.5 μg/m3, respectively. Biomass burning was confirmed by high daily concentration levels of levoglucosan, mannosan, and galactosan (sum equals to 288 ng/m3). Road traffic was also highlighted by the relative abundance of tetracosane and a carbon preference index close to unity as well as by the concentration ratios of PAHs and hopanes. Moreover, phthalates were identified for the first time in Cairo with high concentrations (654 ng/m3) that might be attributable to open waste burning activities. Fatty acids and sugars were also investigated and assigned to cooking activities and primary biogenic sources, respectively. The average concentration of isoprene and β-caryophyllene oxidation products were 0.89 ± 0.83 ng/m3, and 0.01 ± 0.02 ng/m3, respectively. These low values are expected since no pine trees or even forests exist in Egypt. The macrotracer approach was employed alongside Monte Carlo simulation to identify sources of primary OC and evaluate the uncertainties associated with source attribution and OC reconstruction. The findings revealed a strong contribution from cooking (31% of observed OC) and biomass burning (18%), with median reconstructed OC levels showing significant uncertainty (64%) as expected.

Rapid screening of Salmonella typhimurium based on a bacterial surface-imprinted polymer-functionalized bipolar electrode-electrochemiluminescence platform

A bipolar electrode-electrochemiluminescence (BPE-ECL) sensor, utilizing a polydopamine (PDA) bacterial surface-imprinted polymer (SIP), has been developed for the detection of Salmonella typhimurium (S. typhimurium). To fabricate this sensor, dopamine (DA) served as the monomer, while S. typhimurium played a crucial role as the template molecule. Through a precision-tuned electropolymerization process, a polymer film template was seamlessly crafted on the cathode of BPE, encasing the target bacteria within its matrix. Once the template was delicately removed, a molecular surface-imprinted film emerged on the cathode, forming a PDA SIP capture probe that was remarkably adept at recognizing and binding to the target bacteria. When the target bacteria was present on the cathode, the Fc-aptamer-S. typhimurium acted as a signal probe to specifically recognized S. typhimurium. Applying a constant potential to the BPE, the oxidation product Fc+, generated at the cathode, accelerating the luminescence of the [Ru(bpy)3]2+/TPrA system on the anode. The sensor exhibited a remarkable sensitivity, capable of detecting S. typhimurium concentrations ranging from 101 to 106 CFU mL−1, with a detection limit of 10 CFU mL−1.

Oxidation of glyoxal with the Mo-oxime complex in a benzalkonium chloride interface: Raghavan and Srinivasan kinetic model

Gaining an understanding of the glucose oxidation product (glyoxal) interaction with the metal–organic complex in a biological environment is pivotal to its usage. Thus, the glyoxal (Gyx) oxidation with Mo-oxime complex (MC) is studied with the spectrophotometric method, following a pseudo-phase approach. The result highlights the inclusion of hydrolysis, ion catalysis, the neutral primary salt effect, and radical generation as the essential factors in Gyx oxidation, with the exclusion of intermediate species formation. The hydrolysis of Gxy is observed to actively engage MC without charge inhibition as charge-neutral reacting species are involved, thus, implicating neutral primary salt effect where the variation of ionic strength of the system keeps the redox rate unchanged. The involvement of charge-neutral specie at the rate controlling step encouraged electrostatic attraction when Mg2+ ion additive is incorporated into the system, leading to ion catalysis. The generation of free radical from Gxy aids the emergence of formic acid. The zero intercept of Michealis-Menten type plot and the non-appreciable shift in the maximum absorption wavelength of the reaction system and MC rule-out the presence of intermediate species. The contribution of thermodynamic enthalpy is instrumental in the redox process, leading to the formic acid product. The inclusion of benzalkonium chloride (BZC) hastens the Gxy oxidation, which is supported by Raghavan and Srinivasan’s model.

Rubber additives and relevant oxidation products in groundwater in a central China region: Levels, influencing factors and exposure

This study investigated the presence of rubber additives and relevant oxidation products (RAROPs) in groundwater in central China's aboveground river region. Seven RAROPs were detected, and their levels in shallow groundwater showed a mild decreasing trend from the area near the Yellow River (Avg: 8.49 ng·L-1) to the area on the far bank of the Yellow River (Avg: 5.01 ng·L-1). In contrast, deep groundwater's RAROPs contents showed a dramatic decrease to only 0.26 ng·L-1. The dominant contaminant was found to be N-(1, 3-dimethylbutyl) -N′-phenyl -p-phenylenediamine (6PPD). The vicinity of the garages and car parks was often characterized as contamination hotspots. Correlation analyses further indicated that aquaculture was likely to be a potential pathway for shallow groundwater contaminant inputs. The amount of RAROPs intake by humans through groundwater is nearly 30 times different due to the imbalanced development between urban and rural areas. Children were the most vulnerable to RAROPs. Therefore, human activities (transportation, waste tire storage, water resource allocation and utilization patterns, diversion of Yellow River water to aquaculture ponds) may exacerbate RAROPs pollution in groundwater by leaching contaminants through the surface soil. These results are important for developing appropriate utilization and protection strategies for groundwater resources in developing countries.

Perspective on the Oxidative Stress Biomarkers and Antioxidant Defense Strategies

Abstract: Reactive oxygen and nitrogen species are produced via a variety of endogenous and exogenous mechanisms that lead to severe impairment in human diseases. Nevertheless, thanks to the presence of enzymatic and non-enzymatic antioxidants, which in favors of neutralizing these species. Along with several non-enzymatic antioxidants with modest molecular masses, the human body additionally possesses a highly potent intrinsic enzymatic antioxidant system. An imbalance between oxidants and antioxidants in favor of the oxidants, leading to a disruption of redox signaling and control and/or oxidative damage. These oxidative injuries are frequently linked to cancer, aging, and neurological diseases. Direct measurements of the concentrations of reactive species are nearly impossible due to their incredibly short half-lives and fairly expensive systems. Therefore, rather than directly measuring reactive species, products created by oxidative damage to proteins, lipids, and DNA are frequently utilized to estimate the degree of oxidative damage. These oxidative damage products are typically referred to as biomarkers. The assessment of these biomarker concentrations, as well as fluctuations in the concentration of protective antioxidants, might provide significant information for preventing certain diseases and maintaining optimal health. This study aims to summarize the data of the potential biomarkers related to the putative ROS pathway that have been implicated. Additionally, the intervention using therapeutic exogenous antioxidant as defense strategies in balancing the redox reactions and their ramifications has also been discussed.

Detailed Microscopic Reaction Mechanism during the Combustion Process of HAN-Based Propellant.

Hydroxylamine nitrate (HAN)-based propellants, renowned for their high energy efficiency and nontoxic properties, are considered candidates for next-generation green propellants. The ab initio molecular dynamics (AIMD) method was used to theoretically study the thermal decomposition reaction process of the HAN aqueous solution and the system mixed by HAN and fuel methanol/ethylammonium nitrate. The principal reaction pathways of HAN-based propellants are delineated by scrutinizing AIMD trajectory results. HAN-based propellants transition from an ionic state to a neutral state during combustion, and the thermal decomposition of HAN begins with the breakdown of HNO3 itself into ·NO2 radicals and ·OH radicals. Although the thermal decomposition reaction of HAN is complex and a large number of intermediates are produced, only a few key free radicals and small molecules drive the subsequent reaction forward. The thermal decomposition of the fuel lags behind that of HAN in the combustion process of HAN-based propellants. The oxidants such as ·NO2 produced by HAN decomposition react with fuel molecules, and the free radicals produced by the decomposition of oxidative products such as HONO further act as oxidants to react with fuel molecules again.

Impact of Short-Term Exposure to Non-Functionalized Polystyrene Nanoparticles on DNA Methylation and Gene Expression in Human Peripheral Blood Mononuclear Cells

The aim of the present study was to investigate the concentration- and size-dependent effects of non-functionalized polystyrene nanoparticles (PS-NPs) of varying diameters (29 nm, 44 nm, and 72 nm) on specific epigenetic modifications and gene expression profiles related to carcinogenesis in human peripheral blood mononuclear cells (PBMCs) in vitro. This in vitro human-cell-based model is used to investigate the epigenetic effect of various environmental xenobiotics. PBMCs were exposed to PS-NPs at concentrations ranging from 0.001 to 100 µg/mL for 24 h period. The analysis encompassed epigenetic DNA modifications, including levels of 5-methyl-2′-deoxycytidine (5-mdC) and 5-(hydroxymethyl)-2′-deoxycytidine (5-hmdC), as well as the levels of 2′-deoxyuridine (dU) and 5-(hydroxymethyl)-2′-deoxyuridine (5-hmdU) by mass spectrometry methods, methylation in the promoter regions of selected tumor suppressor genes TP53 (P53), CDKN2A (P16), and CDKN1A (P21) and proto-oncogenes (CCND1, BCL2, BCL6), along with the expression profile of the indicated genes by real-time PCR assays. The results obtained revealed no significant changes in global DNA methylation/demethylation levels in PBMCs after short-term exposure to non-functionalized PS-NPs. Furthermore, there were no changes observed in the level of dU, a product of cytosine deamination. However, the level of 5-hmdU, a product of both 5-hmdC deamination and thymine oxidation, was increased at the highest concentrations of larger PS-NPs (72 nm). None of the PS-NPs caused a change in the methylation pattern of the promoter regions of the TP53, CDKN2A, CDKN1A, CCND1, BCL2 and BCL6 genes. However, gene profiling indicated that PS-NPs with a diameter of 29 nm and 44 nm altered the expression of the TP53 gene. The smallest PS-NPs with a diameter of 29 nm increased the expression of the TP53 gene at a concentration of 10 µg/mL, while PS-NPs with a diameter of 44 nm did so at a concentration of 100 µg/mL. An increase in the expression of the CDKN2A gene was also observed when PBMCs were exposed to PS-NPs with 29 nm in diameter at the highest concentration. The observed effect depended on both the concentration and the size of the PS-NPs.

Visible-Light-Induced Divergent Oxygenation of Methylbenzene Utilizing Aryl Halides.

The selective oxidation of methylbenzene to value-added products is of indisputable importance in organic synthesis. Although photocatalytic oxidation reactions of toluene have achieved great success for the preparation of its oxidative products, such as carboxylic acids, benzaldehyde, and benzoate, there remains a lack of a unified photocatalytic system for the selective preparation of these oxidation products. Herein, we report a metal- and additive-free photocatalytic protocol enabled by aryl halides using O2 as a green oxidant for the selective synthesis of the above-mentioned three oxidation products by adjusting the reaction solvent. This strategy features many advantages, including environmentally friendly and mild reaction conditions, broad substrate applicability and functional group tolerance, and potential practical application for the synthesis of aromatic carboxylic drugs and polymer materials and degradation of polystyrene waste. The continuous-flow system was utilized for the oxidation of toluene, which resulted in a reduced reaction time and increased production efficiency. Detailed mechanistic investigation revealed that the hydrogen atom transfer process was facilitated by the bromine radical from aryl halides for further oxidation, and an electron donor-acceptor complex of methylbenzene and aryl halides may exist.

Influence of processing of seitan, tempeh, and firm regular tofu on protein and lipid oxidation and Maillard reaction products formation

The impact of production and cooking on protein oxidation, lipid oxidation and Maillard reaction products (MRPs) generation was evaluated for firm regular tofu, tempeh, and seitan, three plant-based alternatives to meat products. Tofu showed higher content of protein-bound carbonyls (25.5 ± 5.4 nmol/mg protein) indicating higher degree of protein oxidation, while seitan exhibited the lowest content of MRPs like N(6)-carboxymethyllysine, as revealed by LC-MS/MS. Through determination of the peroxide value and thiobarbituric acid reactive substances as well as analysis of volatile oxidation compounds by GC–MS, an overall higher lipid oxidation level was found in tofu. Likewise, a mean 92.2 % depletion of naturally occurring antioxidant tocopherol, assessed by HPLC-DAD, was observed in tofu. Furthermore, acrylamide was detected in tofu at 196.0 ± 15.4 μg/kg after frying at 190 °C. This study, therefore, concluded that practices used in tempeh and seitan processing are promising strategies to limit oxidation and Maillard reactions in food.

CO2 protects cells from iron-Fenton oxidative DNA damage in Escherichia coli and humans

While hydroxyl radical is commonly named as the Fenton product responsible for DNA and RNA damage in cells, here we demonstrate that the cellular reaction generates carbonate radical anion due to physiological bicarbonate levels. In human and Escherichia coli models, their transcriptomes were analyzed by RNA direct nanopore sequencing of ribosomal RNA and chromatography coupled to electrochemical detection to quantify oxidation products in order to follow the bicarbonate dependency in H2O2-induced oxidation. These transcriptomic studies identified physiologically relevant levels of bicarbonate focused oxidation on the guanine base favorably yielding 8-oxo-7,8-dihydroguanine (OG). In human cells, the bicarbonate-dependent oxidation was further analyzed in the metabolome by mass spectrometry, and a glycosylase-dependent qPCR assay to quantify oxidation sites in telomeres. These analyses further identify guanine as the site of oxidation when bicarbonate is present upon H2O2 exposure. Labile iron as the catalyst for forming carbonate radical anion was demonstrated by repeating the bicarbonate-dependent oxidations in cells experiencing ferroptosis, which had a >fivefold increase in redox-active iron, to find enhanced overall guanine-specific oxidation when bicarbonate was present. The complete profiling of nucleic acid oxidation in the genome, transcriptome, and metabolome supports the conclusion that a cellular Fe(II)-carbonate complex redirects the Fenton reaction to yield carbonate radical anion. Focusing H2O2-induced oxidative modification on one pathway is consistent with the highly evolved base excision repair suite of enzymes to locate G-oxidation sites for repair and gene regulation in response to oxidative stress.

Versatile laccase-mimicking enzyme for dye decolorization and tetracyclines identification upon a colorimetric array sensor

In this study, the laccase-mimicking enzyme MnO2/Cu-BDC-His was synthesized by a facile procedure, and was applied in tetracycline antibiotics (TCs) identification and dye degradation. The MnO2/Cu-BDC-His nanozymes effectively recognized phenolic hydroxyl groups in TCs and catalyzed the generation of colored oxidation products with different characteristic absorbance peaks at 350 nm, 525 nm and 600 nm. Different TCs mixtures produced different absorbance intensities at the above wavelengths and exhibited cross-color responses. Consequently, a colorimetric array sensor for the simultaneous identification and detection of TCs with wavelength as the sensing element was established. Unlike the traditional "lock-and-key" detection mode, the array sensor enabled simultaneous multi-analyte detection and identification, which achieved the identification and quantification of mixed TCs in the range of 5–200 µM, providing a premise for its application in lake and soil water. Additionally, the MnO2/Cu-BDC-His nanozymes were also applied in colored dyes decolorization. Therefore, MnO2/Cu-BDC-His nanozymes provided a promising application in environmental monitoring.

Chemical modification of selenium-containing amino acids caused by non-thermal dielectric-barrier discharge atmospheric-pressure plasma.

Since non-thermal atmospheric-pressure ("cold") plasma sources, such as the dielectric-barrier discharge (DBD), have appeared to be remarkably active in wound healing medicine, the elucidation of cold plasma safety and possible secondary undesirable effects becomes of paramount importance. Selenium-containing amino acids, which are commonly incorporated in many enzymes, came in the spotlight for elucidating the plasma impact as easily oxidizable natural targets. The scope of this study was to analyse the impact of non-thermal plasma on selenium-containing amino acids. Moreover, this research examines the emerging role of metals in the context of oxidation potency of reactive species generated by plasma. The dielectric barrier discharge (DBD) was used to treat 4 mM solutions of Se-(methyl)seleno-l-cysteine (1), l-selenomethionine (2) and seleno-l-cystine (3) for varying treatment times to investigate possible degradation products. In this study we used two redox active iron complexes as well as a redox inert zinc complex in order to compare their capacity to affect chemical modifications caused by plasma. The solutions with selenium-containing amino acids after plasma treatment were analyzed by IR spectroscopy, electrospray ionization mass spectrometry (ESI-MS) and High Performance Liquid Chromatography (HPLC). Several oxidation products were observed as a consequence of plasma treatment, namely: Se-(methyl)seleno-l-cysteine (1) and l-selenomethionine (2) were oxidized to selenoxide and selendioxide derivatives, wheres the Se-Se dimer, seleno-l-cystine (3), was converted to Se-cysteine and seleninic acid. Additionally and to our surprise, redox active iron(ii) and iron(iii) complexes as well as the non-redox active zinc(ii) complex caused the same oxidation pattern when added to the plasma treatment mixtures. Finally, a comparison of the results from Se-containing amino acids with those of their S-containing counterparts revealed that Se-containing amino acids are less prone to cold plasma oxidation than S-containing molecules. By elucidating molecular details of plasma-biomolecule interactions herein we aim to contribute to a better understanding of the complex beneficial medical effects of cold plasma treatments.

FEATURES OF CYCLE OPENING IN THE gem-DIHALOGENCYCLOPROPYL DERIVATIVES OF THIOANISOLE IN THE SYSTEM CuSO4/DMSO/H2O

The results of studies on the cleavage of the cyclopropane ring in 2,2-dichloro- and 2,2-dibromocyclopropylmethyl(phenyl)sulfides under the action of copper sulfate in aqueous dimethylformamide are presented. It is shown that under these conditions, when heated at 100-105 °C for 10-11 hours, mixtures of three isomeric chloro(bromo)-allyl alcohols are formed. The ratios of these alcohols were determined by comparing the integral intensities of the proton signals in the 1H NMR spectra and the integral intensities of the chromatograms and are approximately 3.54:3.15:1 for dichloro- and 5.1:3.9:1 for dibromocyclopropyl derivatives. The structure of the isomeric alcohols was proved by the results of NMR 1H analysis and fragmentation in the mass spectra. Under the same conditions, the action of Cu(II)+ ion on the oxidation products of 2,2-dichloro- and 2,2-dibromocyclopropylmethylphenylsulfonyl sulfides did not show ring cleavage according to thin layer chromatography. When the temperature reaches above 150 °C, the corresponding sulfones are charred. The influence of the nature of the halogen on the regioselectivity of the reaction was analyzed. A likely reaction mechanism involves the formation of an allylic cation as a key intermediate. The obtained results expand the understanding of the reactivity of heme-dihalogencyclopropanes and open new perspectives for the synthesis of functionalized organic compounds, in particular, potential biologically active ones. It was found that replacing the phenylthio substituent with a phenylsulfonyl one significantly reduces the reactivity of the cyclopropane ring.

Rice husk-fortified beef sausages: Cholesterol oxidation products, physicochemical properties, and sensory attributes

The effect of rice husk flour (RHF) supplementation on the physicochemical properties, oxidative stability, and sensory attributes of beef sausages was examined. Beef sausages were formulated with either 0 % RHF + 15 % wheat flour (WF), RHF-0; 5 % RHF + 10 % WF, RHF-5; 10 % RHF + 5 % WF, RHF-10, or 15 % RHF + 0 % WF, RHF-15, and cooked at 200 °C for 20 min. RHF supplementation significantly increased dietary fiber while decreasing moisture content (P < 0.05). Beef sausages with RHF had lower L*, a*, TBARS, carbonyl content, hardness, chewiness, and gumminess, and a higher pH (P < 0.05). RHF-10 and RHF-15 sausages exhibited greater cook loss compared to other formulations (P < 0.05). The levels of 7-ketocholesterol decreased with increasing RHF levels, while 7α-hydroxycholesterol and 7-hydroperoxycholesterol were higher in RHF-0 and RHF-10 sausages compared to RHF-5 and RHF-15 sausages (P < 0.05). In addition, RHF improved the taste, juiciness, appearance, and overall acceptance of beef sausages. These findings suggest that RHF can be a valuable ingredient in beef sausages by increasing fiber content, reducing oxidative degradation, and maintaining sensory quality despite some moisture loss.

Enhanced antioxidant activity of selenium-enriched brown rice protein against oxidative stress in mammalian erythrocytes under various cooking conditions

This study investigated the effects of Selenium-enriched brown rice protein on oxidative stress in the mammalian erythrocytes. Selenium-enriched brown rice protein and native rice protein (control) were treated with mice erythrocytes at various cooking processes. The research explored the antioxidant activity of enzymes, including superoxide dismutase (SOD), catalase CAT), and lipid peroxidase (LPO) as well as markers of oxidative damage such as malondialdehyde (MDA). Furthermore, the investigation analyzed the expression of proteins, including nuclear factor erythroid 2-related factor 2 (Nrf2), a principal regulator of the antioxidant response, and Band3, a membrane protein crucial for erythrocyte function. The study also examined the influence of different types of cooking on the effectiveness of selenium-enriched brown rice protein and native rice protein (control). Cooking increased the protection against oxidative damage of red blood cells; high-pressure cooking demonstrated the highest efficacy, followed by microwave cooking and low-pressure cooking. In addition, the results indicated that this protection mechanism might be related to the regulation of antioxidant enzyme activities and gene expressions induced by Peroxiredoxins (PRP) protein, Band3, and Nrf2 genes, leading to decreased lipid peroxidation and oxidative product generation. This contributed to the preservation of RBC integrity and decreased the rate at which it was Hemolysis. Our findings suggest that the protective mechanism of PRP against oxidative damage in RBCs is associated with the regulation of PRP, Band3 protein, and Nrf2 gene expression. This regulation reduces lipid peroxidation, minimizes LPO and MDA production, and preserves cell integrity, ultimately decreasing the hemolysis rate under oxidative stress.

Enzymatic Oxidation of Aflatoxin M1 in Milk Using CotA Laccase.

Aflatoxin M1 (AFM1) in milk poses a significant threat to human health. This study examined the capacity of Bacillus licheniformis CotA laccase to oxidize AFM1. The optimal conditions for the CotA laccase-catalyzed AFM1 oxidation were observed at pH 8.0 and 70 °C, achieving an AFM1 oxidation rate of 86% in 30 min. The Km and Vmax values for CotA laccase with respect to AFM1 were 18.91 μg mL-1 and 9.968 μg min-1 mg-1, respectively. Computational analysis suggested that AFM1 interacted with CotA laccase via hydrogen bonding and van der Waals interactions. Moreover, the oxidation products of AFM1 mediated by CotA laccase were identified as the C3-hydroxy derivatives of AFM1 by HPLC-FLD and UPLC-TOF/MS. Toxicological assessment revealed that the hepatotoxicity of AFM1 was substantially reduced following oxidation by CotA laccase. The efficacy of CotA laccase in removing AFM1 in milk was further tested, and the result showed that the enzyme agent achieved an AFM1 removal rate of 83.5% in skim milk and 65.1% in whole milk. These findings suggested that CotA laccase was a novel AFM1 oxidase capable of eliminating AFM1 in milk. More effort is still needed to improve the AFM1 oxidase activity of CotA laccase in order to shorten the processing time when applying the enzyme in the milk industry.

Photocatalytic Substrate Oxidation Catalyzed by a Ruthenium(II) Complex with a Phenazine Moiety as the Active Site Using Dioxygen as a Terminal Oxidant.

We have developed photocatalytic oxidation of aromatic substrates using O2 as a terminal oxidant to afford only 2e--oxidized products without the reductive activation of O2 in acidic water under visible-light irradiation. A RuII complex (1) bearing a pyrazine moiety as the active site in tetrapyrido[3,2-a:2',3'-c:3″,2″-h:2‴,3‴-j]phenazine (tpphz) as a ligand was employed as a photocatalyst. The active species for the photocatalysis was revealed to be not complex 1 itself but the protonated form, 1-H+, protonated at the vacant diimine site of tpphz. Upon photoexcitation in the presence of an organic substrate, 1-H+ was converted to the corresponding dihydro-intermediate (2-H+), where the pyrazine moiety of the ligand received 2e- and 2H+ from the substrate. 2-H+ was facilely oxidized by O2 to recover 1-H+. Consequently, an oxidation product of the substrate and H2O2 derived from dioxygen reduction were obtained; however, the H2O2 formed was also used for oxidation of 2-H+. In the oxidation of benzyl alcohol to benzaldehyde, the turnover number reached 240 for 10 h, and the quantum yield was determined to be 4.0%. The absence of ring-opening products in the oxidation of cyclobutanol suggests that the catalytic reaction proceeds through a mechanism involving formal hydride transfer. Mechanistic studies revealed that the photocatalytic substrate oxidation by 1-H+ was achieved in neither the lowest singlet excited state nor triplet excited state (S1 or T1) but in the second lowest singlet excited state (S2), i.e., 1(π-π*)* of the tpphz ligand. Thus, the photocatalytic substrate oxidation by 1-H+ can be categorized into unusual anti-Kasha photocatalysis.