Oxidative Conditions Research Articles

22]Pentaphyrins(2.0.1.1.0) Displaying N-Fusion, Pyrrole-Rearrangement, and Dimerization Reactions Upon Oxidation and Metalation.

Exploration of expanded porphyrins with unprecedented reactivities has remained important. Here [22]pentaphyrins(2.0.1.1.0) were synthesized as a constitutional isomer of sapphyrin by acid-catalyzed cyclization of 1,14-dibromo-5,10-diaryltripyrrin with 1,2-di(pyrro-2-ly)ethenes. These pentaphyrins display roughly planar structures and varying aromaticities depending upon the vinylene structures. The 19,20-ditolyl pentaphyrin gave an N-fused product and an unprecedented pyrrole-rearranged product, depending upon the oxidation conditions. Remarkably, upon the metalation with CuCl, the N-fused product and the pyrrole-rearranged product afforded an inner b-b coupled face-to-face CuII complex dimer and an outer b-b coupled lateral CuII complex dimer, respectively, in fairly good yields. Further, [22]pentaphyrin(2.0.1.1.0) fused with a NiII porphyrin was effectively dimerized upon oxidation with MnO2 to give a 16-16' directly linked dl-dimer.

Formation of the Calpain-1/Calpastatin Complex Promotes Activation of Calpain-1 under Oxidizing Conditions.

Calpains are cysteine proteinases responsible for many biological roles in muscle, including protein degradation, muscle growth, and myoblast fusion. Calpains are inhibited by calpastatin, an endogenous inhibitor. Other factors, such as variations in pH, ionic strength, and oxidation influence calpain activity. This study aimed to determine the extent to which oxidation influences calpastatin inhibition of calpain-1. A series of order of addition assays were used to determine calpain-1 calcium activation and autolysis after exposure to an oxidizing agent (N-ethylmaleimide [NEM] or hydrogen peroxide [H2O2]. In the first series, purified calpastatin was added to the assay before or after oxidizing exposure at 165mM NaCl, pH 6.5. In the second series, incubation buffer ionic strength (165mM or 295mM NaCl) was evaluated. The inhibitory activities of purified porcine calpastatin, purified human calpastatin domain I, or a subdomain B inhibitor peptide were evaluated in the third series. In the fourth series, a maleimide-polyethylene glycol molecule (MAL-PEG;MW=5000 Dalton) was used to evaluate the accessibility of free sulfhydryl groups and tagging of calpain-1 under each condition through a molecular weight shift assay. Results from this study indicate that autolysis of calpain-1, when used as an indicator of activation, occurred when the calpain-1/calpastatin complex was exposed to an oxidant or cysteine modifier such as NEM. However, when calpain-1 was exposed to the cysteine modifier before calpastatin, autolysis of calpain-1 did not occur or was significantly decrased (P < 0.05). Irreversible modification of cysteine residues by NEM prevented activation of calpain-1 in the absence of calpastatin, but if the cysteine modification is potentially reversible (H2O2), calpain-1 activity can be recovered. Results from this study indicate that when calpastatin is bound to calpain-1, calpain-1 activation can occur even after being exposed to a cysteine modifier (NEM) or hydrogen peroxide (H2O2). Calpain-1 is not tagged with maleimide-polyethylene glycol (MAL-PEG) in the presence of calpastatin, indicating that calpastatin blocks or covers free cysteines on calpain-1 from modification. Moreover, exposure to calpain-1/calpastatin complex with a cysteine modifier allows activation of calpain-1, indicating that the inhibitory action of calpastatin is compromised. These results indicate a regulatory role for calpastatin that is not inhibitory but protective for calpain-1.

Loading rutin on surfaces by the layer-by-layer assembly technique to improve the oxidation resistance and osteogenesis of titanium implants in osteoporotic rats.

The purpose of this study was to construct a rutin-controlled release system on the surface of Ti substrates and investigate its effects on osteogenesis and osseointegration on the surface of implants. The base layer, polyethylenimine (PEI), was immobilized on a titanium substrate. Then, hyaluronic acid (HA)/chitosan (CS)-rutin (RT) multilayer films were assembled on the PEI using layer-by-layer (LBL) assembly technology. We used scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy and contact angle measurements to examine all Ti samples. The drug release test of rutin was also carried out to detect the slow-release performance. The osteogenic abilities of the samples were evaluated by experiments on an osteoporosis rat model and MC3T3-E1 cells. The results (SEM, FTIR and contact angle measurements) all confirmed that the PEI substrate layer and HA/CS-RT multilayer film were effectively immobilized on titanium. The drug release test revealed that a rutin controlled release mechanism had been successfully established. Furthermore, the in vitro data revealed that osteoblasts on the coated titanium matrix had greater adhesion, proliferation, and differentiation capacity than the osteoblasts on the pure titanium surface. When MC3T3-E1 cells were exposed to H2O2-induced oxidative stress in vitro, cell-based tests revealed great tolerance and increased osteogenic potential on HA/CS-RT substrates. We also found that the HA/CS-RT coating significantly increased the new bone mass around the implant. The LBL-deposited HA/CS-RT multilayer coating on the titanium base surface established an excellent rutin-controlled release system, which significantly improved osseointegration and promoted osteogenesis under oxidative stress conditions, suggesting a new implant therapy strategy for patients with osteoporosis.&#xD.

The Effect of Cinnamon Bark Extract (Cinnamomum burmanii) on Blood Malondialdehyde (MDA) Levels in Hyperglycemia Rats

Hyperglycemia is a condition where blood glucose levels increase beyond normal limits. Hyperglycemia can induce oxidative stress conditions caused by an increase in free radicals and a reduction in endogenous antioxidant defenses, characterized by an increase in blood malondialdehyde levels. Oxidative stress causes malondialdehyde levels to increase and endogenous antioxidants to decrease, therefore the body needs exogenous antioxidants. One plant that is rich in antioxidants is cinnamon bark, where cinnamon bark can increase antioxidant capacity. This study aims to examine the effect of cinnamon bark extract (Cinnamomum burmanii) on reducing blood malondialdehyde levels in hyperglycemic rats. This research is experimental research using the Post Test-Only Control Group design. Male Wistar rats were divided into 5 groups (n=6), negative control (K-), positive control (K+), P1 (dose 100 mg/kgBW), P2 (dose 200 mg/kgBW), P3 (dose 300 mg/kgBW). The normality test was carried out using the Shapiro-Wilk test followed by One Way Anova and Kruskal Wallis. The results showed that cinnamon bark (Cinnamomum burmanii) was proven to be able to reduce blood malondialdehyde levels, where the optimal dose was P1 (dose 100mg/kgBW) whereas in the P1 group, the average malondialdehyde levels were found to be the lowest compared to other treatment groups. Keywords: Hyperglycemia; cinnamon bark; malondialdehyde; oxidative stress

LC and LC-MS/MS Studies for the Separation and Identification of Impurities and Degradation Products of Betaxolol.

Betaxolol (Bx) is a selective β1 receptor blocker used in the treatment of hypertension and glaucoma. The aim of the present work was to demonstrate an approach involving use of liquid chromatography (LC) and liquid chromatography-electrospray ionization mass spectrometry (LC-ESI/MS) for the simultaneous separation, identification and characterization of impurities and of degradation products of betaxolol without their isolation from the reaction mixtures. At optimum condition, and according to ICH guidelines, the limit of detection (LOD) and limit of quantification (LOQ) for Bx are found to be 5.46 and 16.54μgmL-1, respectively. However, the LOD and LOQ for the major degradation product P6 were 2.15 and 6.53μgmL-1. Betaxolol was subjected to hydrolytic (acidic and basic) and oxidative, stress conditions according to International Conference on Harmonization (ICH) guideline Q1A (R2), and as results, the drug was found to be labile in acidic, basic and oxidative stress conditions. Based on LC-ESI/MS analysis, the found results revealed that Bx decomposes in acidic, basic and oxidizing environments. All degradation products were identified with the help of their fragmentation pattern and the masses obtained upon the MS analysis.

The Potential of Selenium-Based Therapies for Ocular Oxidative Stress

Oxidative stress plays a critical role in the development of chronic ocular conditions including cataracts, age-related macular degeneration, and diabetic retinopathy. There is a need to explore the potential of topical antioxidants to slow the progression of those conditions by mediating oxidative stress and maintaining ocular health. Selenium has attracted considerable attention because it is a component of selenoproteins and antioxidant enzymes. The application of selenium to a patient can increase selenoprotein expression, counteracting the effect of reactive oxygen species by increasing the presence of antioxidant enzymes, and thus slowing the progression of chronic ocular disorders. Oxidative stress effects at the biomolecular level for prevalent ocular conditions are described in this review along with some of the known defensive mechanisms, with a focus on selenoproteins. The importance of selenium in the eye is described, along with a discussion of selenium studies and uses. Selenium’s antioxidant and anti-inflammatory qualities may prevent or delay eye diseases. Recent breakthroughs in drug delivery methods and nanotechnology for selenium-based ocular medication delivery are enumerated. Different types of selenium may be employed in formulations aimed at managing ocular oxidative stress conditions.

Improvement of the oxidative stability of edible oils through enzymatic esterification with hydroxytyrosol‐rich extract

AbstractOxidative degradation is a common issue of commercial edible oils that results in rancidity, downgrading the organoleptic characteristics of food matrices. The aim of this study was the enzymatic modification of common vegetable oils (pomace olive and sunflower oil) with polyphenolic extract to prepare functional oils enriched with bioactive phenolipids. Under that scope, an agro‐industrial effluent, olive mill wastewater, was used as source to recover phenolic compounds. The recovery of hydroxytyrosol and tyrosol reached up to 81.2% ± 0.3% and 98.3% ± 0.2%, respectively. Further, immobilized lipase was used to catalyze the one‐step acylation of these phenolic antioxidants into the oils with the aim of enhancing their stability under accelerated oxidation conditions. The optimum parameters of the bioconversion were found to be 0.1% (w/w) immobilized lipase, 24h of incubation at 50°C under orbital shaking reaching high conversion yields for both phenolic compounds (≥94%). The results also highlighted that the extract‐modified oils presented notable thermooxidative stability at 60°C for 28 days compared to the control and synthetic antioxidant‐enriched oils, as demonstrated by several analytical (conjugated dienes, thiobarbituric reactive substances), chromatographic (solid‐phase microextraction gas chromatography/mass spectroscopy), and spectroscopic (fluorescence, attenuated total reflectance) techniques, giving new insights regarding the preservation of edible oils.Practical Application: Htyr has recently gained much attention as an active ingredient of food matrices for industrial applications due to its high antioxidant/antiradical activity. A major drawback of Htyr exploitation is the high market price and its solubility. Meanwhile, several edible oils are prone to autooxidation during transport, stock management, and household storage. The proposed one‐step biocatalytic process aims to enhance the lipophilicity and bioactivity of Htyr in bulk oil systems, making the use of this potent antioxidant compound feasible. This approach shows promise in extending the shelf life of common oils and highlights the advantages of by‐product management. Moreover, these functional oils can be applied for the preparation of sauces, bakery products, food supplements, and so on, as the bioactive ingredients that are present in them can delay the oxidative cascade reactions and, thus, the spoilage of the products, whereas the whole process meets the requirements of circular economy and green chemistry.

Volatility and chemical composition of secondary organic aerosol derived from acenaphthylene and acenaphthene under various oxidant conditions

Acenaphthene (ACE) and acenaphthylene (ACY), distinguished by their unique structures, exhibit high reactivity among polycyclic aromatic hydrocarbons (PAHs). Particularly, the rapid ozonolysis of the carbon-carbon double bond in ACY and the swift oxidation of the fused cyclopenta ring in both ACE and ACY by NO3 underscore their distinct atmospheric fate. Through the utilization of a thermo denuder and high-resolution mass spectrometry, the chemical composition and volatility of four types of secondary organic aerosols (SOA) derived from ACE and ACY are investigated. The chemical composition of SOA formed by ACY ozonolysis is characterized by low O: C ratios and high unsaturation, suggesting the retention of aromatic structures. This leads to measured high SOA volatility and is consistent with the low reactivity of O3 with aromatic compounds. In contrast to ozonolysis, the reaction of NO3 with ACY could yield SOA with very low volatility, characterized by abundant dimers and highly oxidized products. Furthermore, the prevalence of compounds with 11 carbon atoms suggests the presence of complex mechanisms in the ACY oxidation process initiated by NO3, where dealkylation reactions and cleavage reactions may be pivotal. The diverse chemical composition and volatility of SOA from ACE and ACY reacting with NO3 radicals highlight the substantial impact of precursor structure on SOA chemical composition, particularly concerning the presence of active carbon-carbon double bonds. The higher O: C ratio of SOA from OH-initiated oxidation of ACE indicates the significant role of OH in the oxidation of PAHs. These findings offer valuable insights into the atmospheric fate of these PAHs, underscoring the necessity for a comprehensive understanding of their degradation processes and the formation of SOA.

Analytical Method Development and Dermal Absorption of 4-Amino-3-Nitrophenol (4A3NP), a Hair Dye Ingredient under the Oxidative or Non-Oxidative Condition

The chemical 4-amino-3-nitrophenol (4A3NP) is classified as an amino nitrophenol and is primarily utilized as an ingredient in hair dye colorants. In Korea and Europe, it is exclusively used in non-oxidative or oxidative hair dye formulations, with maximum allowable concentrations of 1% and 1.5%, respectively. Despite this widespread use, risk assessment of 4A3NP has not been completed due to the lack of proper dermal absorption data. Therefore, in this study, both the analytical method validation and in vitro dermal absorption study of 4A3NP were conducted following the guidelines provided by the Korea Ministry of Food and Drug Safety (MFDS). Before proceeding with the dermal absorption study, analytical methods were developed for the quantitation of 4A3NP through multiple reaction monitoring (MRM) via liquid chromatography-mass spectrometry (LC-MS) in various matrices, including swab wash (WASH), stratum corneum (SC), skin (SKIN, comprising the dermis and epidermis), and receptor fluid (RF). These developed methods demonstrated excellent linearity (R2 = 0.9962–0.9993), accuracy (93.5–111.73%), and precision (1.7–14.46%) in accordance with the validation guidelines.The dermal absorption of 4A3NP was determined using Franz diffusion cells with mini-pig skin as the barrier. Under both non-oxidative and oxidative (6% hydrogen peroxide (H2O2): water, 1:1) hair dye conditions, 1% and 1.5% concentrations of 4A3NP were applied to the skin at a rate of 10 μL/cm2, respectively. The total dermal absorption rates of 4A3NP under non-oxidative (1%) and oxidative (1.5%) conditions were determined to be 5.62 ± 2.19% (5.62 ± 2.19 μg/cm2) and 2.83 ± 1.48% (4.24 ± 2.21 μg/cm2), respectively.

Bioinspired Water Preorganization in Confined Space for Efficient Water Oxidation Catalysis in Metallosupramolecular Ruthenium Architectures.

ConspectusNature has established a sustainable way to maintain aerobic life on earth by inventing one of the most sophisticated biological processes, namely, natural photosynthesis, which delivers us with organic matter and molecular oxygen derived from the two abundant resources sunlight and water. The thermodynamically demanding photosynthetic water splitting is catalyzed by the oxygen-evolving complex in photosystem II (OEC-PSII), which comprises a distorted tetramanganese-calcium cluster (CaMn4O5) as catalytic core. As an ubiquitous concept for fine-tuning and regulating the reactivity of the active site of metalloenzymes, the surrounding protein domain creates a sophisticated environment that promotes substrate preorganization through secondary, noncovalent interactions such as hydrogen bonding or electrostatic interactions. Based on the high-resolution X-ray structure of PSII, several water channels were identified near the active site, which are filled with extensive hydrogen-bonding networks of preorganized water molecules, connecting the OEC with the protein surface. As an integral part of the outer coordination sphere of natural metalloenzymes, these channels control the substrate and product delivery, carefully regulate the proton flow by promoting pivotal proton-coupled electron transfer processes, and simultaneously stabilize short-lived oxidized intermediates, thus highlighting the importance of an ordered water network for the remarkable efficiency of the natural OEC.Transferring this concept from nature to the engineering of artificial metal catalysts for fuel production has fostered the fascinating field of metallosupramolecular chemistry by generating defined cavities that conceptually mimic enzymatic pockets. However, the application of supramolecular approaches to generate artificial water oxidation catalysts remained scarce prior to our initial reports, since such molecular design strategies for efficient activation of substrate water molecules in confined nanoenvironments were lacking. In this Account, we describe our research efforts on combining the state-of-the art Ru(bda) catalytic framework with structurally programmed ditopic ligands to guide the water oxidation process in defined metallosupramolecular assemblies in spatial proximity. We will elucidate the governing factors that control the quality of hydrogen-bonding water networks in multinuclear cavities of varying sizes and geometries to obtain high-performance, state-of-the-art water oxidation catalysts. Pushing the boundaries of artificial catalyst design, embedding a single catalytic Ru center into a well-defined molecular pocket enabled sophisticated water preorganization in front of the active site through an encoded basic recognition site, resulting in high catalytic rates comparable to those of the natural counterpart OEC-PSII.To fully explore their potential for solar fuel devices, the suitability of our metallosupramolecular assemblies was demonstrated under (electro)chemical and photocatalytic water oxidation conditions. In addition, testing the limits of structural diversity allowed the fabrication of self-assembled linear coordination oligomers as novel photocatalytic materials and long-range ordered covalent organic framework (COF) materials as recyclable and long-term stable solid-state materials for future applications.

Bioaccumulation of arsenic in fish (Labeo rohita) in presence of periphyton: ameliorative effect on oxidative stress, physiological condition, immune response and risk assessment.

The present study explores the use of periphyton to ameliorate toxic properties of arsenic (As) to Labeo rohita and also assesses the human food safety aspects. Fish were introduced to arsenite [As(III)] contaminated water (0.3 and 3mg/L) along with periphyton. Biochemical, physiological and immunological parameters, including gene expression, were assessed after 30days of exposure. Periphyton incorporation significantly improved (p < 0.05) the adverse effects of As on respiration, NH3 excretion and brain AChE activity by reducing oxidative stress and As bioaccumulation. The presence of periphyton in As(III) exposed fish (3mg/L) increased the immune response (Immunoglobulin M and Complement C3) in the serum and the regulation of the respective immune genes in the anterior kidney was found to be similar to the control. A speciation study using LC-ICP-MS confirmed the high accumulation of As by periphyton (5.0-31.9μg/g) as arsenate [As (V)], resulting in a lower amount of As in fish muscle. The calculated human health risk indices, Target Hazard Quotient (THQ) and Target Cancer risk (TCR) indicate that fish grown in periphyton-treated water may lower the human health risks associated with As. The study signifies the importance of periphyton-based aquaculture systems in As contaminated regions for safe fish production with enhanced yield.

Development and Validation of Fast and Sensitive RP-HPLC Stability-Indicating Method for Quantification of Piroxicam in Bulk Drug.

A simple, rapid, sensitive, and cost-effective green solvent-assisted reverse-phase high-performance liquid chromatographic technique, coupled with a photodiode array detector, was developed and validated for the estimation of piroxicam (PRXM). The chromatographic separation was achieved by using a C-18 (250 × 4.6) mm, 5-μm stationary phase and a mobile phase consisting of methanol and 0.1% ortho-phosphoric acid in water in a ratio of (80:20) v/v at a flow rate of 1ml/min. The detection was carried out at a wavelength of 254nm with a constant injection volume of 10μL throughout the analysis. The calibration curve was observed to be linear over the optimum concentration range of 50-300μgmL-1, with an R2 value of 0.9995. The developed method was validated as per the International Council for Harmonisation (ICH) Q2 (R1) guideline. Various parameters like selectivity/specificity, accuracy/recovery, linearity, precision, detection limit, quantitation limit, robustness and stability of analyte in solution were performed for the method validation. The PRXM was evaluated under stressed conditions, including acidic, basic, oxidative, thermal and photolytic, as per ICH Q1 (R2) guidelines. Significant degradation was observed in acidic and basic degradation conditions. Conversely, the drug substance showed stability when exposed to oxidative, photolytic and thermal degradation conditions.

CdSe/ZnS Quantum Rods (QRs) and Phenyl Boronic Acid BODIPY as Efficient Förster Resonance Energy Transfer (FRET) Donor-Acceptor Pair.

The reversibility of the covalent interaction between boronic acids and 1,2- or 1,3-diols has put the spotlight on this reaction for its potential in the development of sensors and for the fishing of bioactive glycoconjugates. In this work, we describe the investigation of this reaction for the reversible functionalization of the surface of CdSe/ZnS Quantum Rods (QRs). With this in mind, we have designed a turn-off Förster resonance energy transfer (FRET) system that ensures monitoring the extent of the reaction between the phenyl boronic residue at the meso position of a BODIPY probe and the solvent-exposed 1,2-diols on QRs' surface. The reversibility of the corresponding boronate ester under oxidant conditions has also been assessed, thus envisioning the potential sensing ability of this system.

The effects of oxidative stress and intracellular calcium on mitochondrial permeability transition pore formation in equine spermatozoa

AbstractThe in vitro storage of stallion spermatozoa for use in artificial insemination leads to oxidative stress and imbalances in calcium homeostasis that trigger the formation of the mitochondrial permeability transition pore (mPTP), resulting in premature cell death. However, little is understood about the dynamics and the role of mPTP formation in mammalian spermatozoa. Here, we identify an important role for mPTP in stallion sperm Ca2+ homeostasis. We show that stallion spermatozoa do not exhibit “classical” features of mPTP; specifically, they are resistant to cyclosporin A‐mediated inhibition of mPTP formation, and they do not require exogenous Ca2+ to form the mPTP. However, chelation of endogenous Ca2+ prevented mPTP formation, indicating a role for intracellular Ca2+ in this process. Furthermore, our findings suggest that this cell type can mobilize intracellular Ca2+ stores to form the mPTP in response to low Ca2+ environments and that under oxidative stress conditions, mPTP formation preceded a measurable increase in intracellular Ca2+, and vice versa. Contrary to previous work that identified mitochondrial membrane potential (MMP) as a proxy for mPTP formation, here we show that a loss of MMP can occur independently of mPTP formation, and thus MMP is not an appropriate proxy for the detection of mPTP formation. In conclusion, the mPTP plays a crucial role in maintaining Ca2+ and reactive oxygen species homeostasis in stallion spermatozoa, serving as an important regulatory mechanism for normal sperm function, thereby contraindicating the in vitro pharmacological inhibition of mPTP formation to enhance sperm longevity.

The evolution of crystal‐poor rhyolite in the middle Okinawa Trough and its implications for the state of magma chamber

The crystal‐poor rhyolitic pumice is the product of extreme magma differentiation and is characterized by highly vesicular, honeycomb‐like structure. However, little is known about the evolutionary history and the time of volatile saturation of the pumice‐forming melt. A crystal‐poor rhyolitic pumice (TVG7‐1) has been collected from the Yoron Hole hydrothermal field in the middle Okinawa Trough, a young continental margin back‐arc basin in the western Pacific. This study conducted a detailed analysis on the texture and in situ chemical composition of plagioclase, orthopyroxene and Fe‐Ti oxides to reveal the evolution process, storage state and eruption triggers of eruptible silicic melt. Texture and zoning of specific minerals and mineral populations suggest a magmatic evolution history of open system. Additionally, the hollow reentrant texture, as well as results from plagioclase‐liquid hygrometers, confirm a water‐rich melt pocket. The exsolution of volatiles (H2O, etc.), in this melt pocket, will contribute to local oxidation conditions, which may have been recorded by the concordant behaviour of FeO and An in plagioclase. Then, the overpressure caused by volatile exsolution would destabilize the magma chamber, which will eventually be broken by magma mixing/recharge, and lead to violent melt evacuation. Consequently, crystal size distribution (CSD) provides a new perspective on understanding the kinetic effect of magma mixing/recharge in the Okinawa Trough, especially on the mineral populations. Our study reveals the petrogenesis of crystal‐poor rhyolite within the framework of the mush model, refines the magma evolution history and demonstrates that pumice magma reaches volatile saturation before the eruption.

High-temperature oxidation behaviours of rare earth-based pyrochlore structured A2B2O7/yttria-stabilized zirconia thermal barrier coatings

Addressing the challenge of cost-effectively synthesizing stable thermal barrier coating materials has been a significant hurdle. This study describes the bulk synthesis of stannate-based pyrochlore compounds, specifically erbium tin oxide (Er2Sn2O7) and yttrium tin oxide (Y2Sn2O7). These synthesized pyrochlore oxides and commercially available yttria-stabilized zirconia (YSZ) were coated onto nickel super alloy. The coated specimens were subjected to thermal oxidation kinetics studies at 900 ± 5°C for 200 h, and alterations in physico-chemical characteristics, modifications in surface morphology, and variations in the composition of thermal barrier coating (TBCs) before and after exposure to oxidation conditions were evaluated. Oxidation kinetics results demonstrate that Er2Sn2O7 pyrochlore oxide has better performance than other Y2Sn2O7 and commercial YSZ TBC materials in high-temperature thermal barrier systems.

Microstructure and coloration mechanism of TC11 aerospace titanium alloy ultra-thin thermal oxide films

This study explores the microstructure and coloration mechanism of high-saturation structural colors in ultra-thin oxide films formed on TC11 aerospace titanium alloy near permissible engineering temperatures. Utilizing optical microscopy (OM), spectrophotometry, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), focused ion beam (FIB), transmission electron microscopy (TEM), and energy dispersive spectrometer (EDS), the optical properties, thickness, and microstructure of the oxide films were examined. The research posits a coloration theory grounded in zero-order Fabry-Pérot resonance-enhanced absorption. Key findings reveal a color transition in the oxide films from golden to light blue as oxidation conditions vary from 450 °C for 5 hours to 550 °C for 60 hours, with an average thickness ranging from 16.3 nm to 63.4 nm. Despite changes in oxidation conditions, the film's structure remains consistent and uniform. It predominantly consists of Brookite-type TiO2, TiO and Al2O3, with trace amounts of MoO2 and MoO3. The film's color is independent of its structural composition and instead related to its thickness, influencing the absorption wavelength per the Fabry-Pérot model, which closely matches the observed absorption wavelengths. Notably, oxidation acceleration between 30 to 60 hours at 550 °C heralds the commencement of a deviation from the coloration mechanism of the oxide film based on the Fabry-Pérot cavity.

Identification of major degradation products of Clorsulon drug substance including its degradation pathways by high resolution mass spectrometry and NMR

Clorsulon is an effective anthelmintic drug substance extensively used in the treatment of parasitic infestations in both cattle and sheep. An in-depth investigation of Clorsulon’s degradation products (DPs) was carried out through forced degradation study to comprehend its degradation path. A total of eight degradation products were separated under various stress degradation conditions. Structural elucidation of these DPs was conducted using ultra-high performance liquid chromatography-high resolution mass spectrometry (UHPLC-HRMS), and their fragmentation patterns were compared to that of the parent compound. Adequate amount of DP-4 was isolated and purified by semi-preparative high-performance liquid chromatography (HPLC) methods. Subsequently, it was examined in detail using both 1D and 2D NMR (nuclear magnetic resonance spectroscopy). Most probable mechanistic pathways for the formation of degradation products under various stress degradation conditions were proposed to better understand the degradation profile. Based on the results of the stress study, Clorsulon drug substance was found to be unstable under photolytic and oxidative conditions. Understanding Clorsulon's degradation pathway is essential for determining shelf-life prediction of finished product, safety and efficacy assurance, and guiding the development of stable, high-quality formulations.

Melatonin regulates the antioxidant capacity of sheep granulosa cells through a novel uORF-Nrf2aa mediated Nrf2/KEAP1 pathway

Ovarian dysfunction stands as a prevalent contributor to female infertility, with its etiology intertwined with genetic, autoimmune, and environmental factors. Within the ovarian follicles, granulosa cells (GCs) represent the predominant cell population. Alterations in GCs, notably oxidative stress (OS) and the consequential surge in reactive oxygen species (ROS), play pivotal roles in the orchestration of ovarian function. Nrf2aa, a newly identified upstream open reading frame (uORF), is situated within the 5′ untranslated region (5'UTR) of sheep Nrf2 mRNA and is regulated by melatonin, a crucial intrafollicular antioxidant. In this study, we have noted that Nrf2aa has the capacity to encode a peptide and exerts a negative regulatory effect on the translation efficiency (TE) of the Nrf2 CDs region. Further in vitro experiments, we observed that interfering with Nrf2aa can enhance the cellular functionality of GCs under 3-np-induced oxidative stress, while overexpressing Nrf2aa has the opposite effect. Furthermore, overexpression of Nrf2aa counteracts the rescuing effect of melatonin on the cellular functions of GCs under oxidative stress conditions, including estrogen secretion, proliferation, apoptosis, and many more. Finally, we confirmed that Nrf2aa, by regulating the expression of key proteins in the Nrf2/KEAP1 signaling pathway, further modulates the antioxidant levels in GCs.

Screening and evaluation of antioxidants for retinal pigment epithelial cell protection: L-ergothioneine as a novel therapeutic candidate through NRF2 activation

The continual exposure of retinal tissues to oxidative stress leads to discernible anatomical and physiological alterations. Specifically, the onslaught of oxidative damage escalates the irreversible death of retinal pigmented epithelium (RPE) cells, pinpointed as the fundamental pathological event in dry age-related macular degeneration (AMD). There is a conspicuous lack of effective therapeutic strategies to counteract this degenerative process. This study screened a library of antioxidants for their ability to protect RPE cells against oxidative stress and identified L-ergothioneine (EGT) as a potent cytoprotective agent. L-ergothioneine provided efficient protection against oxidative stress-damaged RPE and maintained cell redox homeostasis and normal physiological functions. It maintained the normal structure of the retina in mice under oxidative stress conditions. Transcriptomic analysis revealed that EGT counteracted major gene expression changes induced by oxidative stress. It upregulated antioxidant gene expression and inhibited NRF2 translocation. The inhibition of NRF2 abolished EGT's protective effects, suggesting that NRF2 activation contributes to its mechanism of action. In conclusion, we identified EGT as a safe and effective small-molecule compound that is expected to be a novel antioxidative agent for treating AMD.