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Melatonin is a small natural compound, so called a neuro‐hormone that is synthesized mainly in pineal gland in animals. Its main role is to master the clock of the body, under the surveillance of light. In other words, it transfers the information concerning night and day to the peripheral organs which, without it, could not "know" which part of the circadian rhythm the body is in. Besides its main circadian and circannual rhythms mastering, melatonin is reported to be a radical scavenger and/or an antioxidant. Because radical scavengers are chemical species able to neutralize highly reactive and toxic species such as reactive oxygen species, one would like to transfer this property to living system, despite impossibilities already largely reported in the literature. In the present commentary, we refresh the memory of the readers with this notion of radical scavenger, and review the possible evidence that melatonin could be an in vivo radical scavenger, while we only marginally discuss here the fact that melatonin is a molecular antioxidant, a feature that merits a review on its own. We conclude four things: (i) the evidence that melatonin is a scavenger in acellular systems is overwhelming and could not be doubted; (ii) the transposition of this property in living (animal) systems is (a) theoretically impossible and (b) not proven in any system reported in the literature where most of the time, the delay of the action of melatonin is over several hours, thus signing a probable induction of cellular enzymatic antioxidant defenses; (iii) this last fact needs a confirmation through the discovery of a nuclear factor—a key relay in induction processes—that binds melatonin and is activated by it and (iv) we also gather the very important description of the radical scavenging capacity of melatonin in acellular systems that is now proven and shared by many other double bond‐bearing molecules. We finally discussed briefly on the reason—scientific or else—that led this description, and the consequences of this claim, in research, in physiology, in pathology, but most disturbingly in therapeutics where a vast amount of money, hope, and patient bien‐être are at stake. [ABSTRACT FROM AUTHOR]

High concentrations of glutamate induce neurotoxicity by eliciting reactive oxygen species (ROS) generation and intracellular Ca2+ influx. The disruption of Ca2+ homeostasis in the endoplasmic reticulum (ER) evokes ER stress, ultimately resulting in neuronal dysfunction. Additionally, glutamate participates in the development of neurodegenerative diseases, such as Alzheimer's and Parkinson's diseases. Peroxiredoxins (Prxs) are members of a family of antioxidant enzymes that protect cells from neurotoxic factor-induced apoptosis by scavenging hydrogen peroxide (H2O2). Prx4 is located in the ER and controls the redox condition within the ER. The present study investigated the protective effects of Prx4 against glutamate-induced neurotoxicity linked to ER stress. HT22 cells in which Prx4 was either overexpressed or silenced were used to elucidate the protective role of Prx4 against glutamate toxicity. The expression of Prx4 in HT22 cells was significantly increased in response to glutamate treatment, while ROS scavengers and ER chemical chaperones reduced Prx4 levels. Moreover, Prx4 overexpression reduces glutamate-induced apoptosis of HT22 cells by inhibiting ROS formation, Ca2+ influx, and ER stress. Therefore, we conclude that Prx4 has protective effects against glutamate-induced HT22 cell damage. Collectively, these results suggest that Prx4 could contribute to the treatment of neuronal disorders. [ABSTRACT FROM AUTHOR]

Interaction of amorphous and crystalline TiO2 ultrafine particles (2–6 nm) with rutin results in the formation of colored nanomaterials of an excellent dispersity and enhanced colloidal stability in aqueous media. The FTIR and Raman spectra confirmed attachment of the rutin ligand via vicinal hydroxyl groups in a catechol-like fashion. The binding of rutin to amorphous TiO2 gives rise to spontaneous crystallization of the parent nanoparticles into hydrogen titanates (H2Ti3O7 and H2Ti12O25). Such structural transformations result in photosensitization toward visible light with enhanced efficiency of the charge separation and interfacial charge transfer processes, confirmed by detailed photoelectrochemical studies of the examined nanomaterials. The effectiveness of the photocatalytic ROS generation reactions was also strongly influenced by hydrogen peroxide, which plays a double role of a reactant prone to reduction and generation of hydroxyl radicals or a redox agent destroying the intra-band gap electronic states, suppressing thereby charge recombination. The photoinduced charge transfer processes lead to generation of various reactive oxygen species, which were detected by EPR using DMPO spin trap (HOO· detection) and in the reaction with terephthalic acid acting as a chemical scavenger (HO· detection). Complexation of TiO2 particles with rutin shifts the photogeneration of hydroperoxyl (HOO·) and hydroxyl (HO·) radicals toward visible light (λ > 400 nm). A triple effect of rutin attachment to titania was established. It consists in pronounced photosensitization, promotion of crystallization and enhancement of the colloidal stability of ultrafine titania particles. Environmental implications of these assets on the photoinduced redox reactions with hydrogen peroxide in aqueous solutions upon UV or visible light irradiation were also discussed. [ABSTRACT FROM AUTHOR]

Plants exposed to hostile environmental conditions such as drought or extreme temperatures usually undergo oxidative stress, which has long been assumed to significantly contribute to the damage suffered by the organism. Reactive oxygen species (ROS) overproduced under stress conditions were proposed to destroy membrane lipids and to inactivate proteins and photosystems, ultimately leading to cell death. Accordingly, considerable effort has been devoted, over the years, to improve stress tolerance by strengthening antioxidant and dissipative mechanisms. Although the notion that ROS cause indiscriminate damage in vivo has been progressively replaced by the alternate concept that they act as signaling molecules directing critical plant developmental and environmental responses including cell death, the induction of genes encoding antioxidant activities is commonplace under many environmental stresses, suggesting that their manipulation still offers promise. The features and consequences of ROS effects depend on the balance between various interacting pathways including ROS synthesis and scavenging, energy dissipation, conjugative reactions, and eventually reductive repair. They represent many possibilities for genetic manipulation. We report, herein, a comprehensive survey of transgenic plants in which components of the ROS-associated pathways were overexpressed, and of the stress phenotypes displayed by the corresponding transformants. Genetic engineering of different stages of ROS metabolism such as synthesis, scavenging, and reductive repair revealed a strong correlation between down-regulation of ROS levels and increased stress tolerance in plants grown under controlled conditions. Field assays are scarce, and are eagerly required to assess the possible application of this strategy to agriculture. [ABSTRACT FROM AUTHOR]

Graphical abstract A series of novel benzoisoselenazol-containing arenobufagin hybrids were designed, synthesized and their in vitro cytotoxicity for cancer cell lines and AC16 cell line, as well as their ROS scavenge activities were evaluated. Among them, 6d and 6f exhibited ROS scavenge activities and less cardiotoxcity. Highlights • A series of novel benzoisoselenazol-containing arenobufagin hybrids (6a – 6f) were synthesized by employing a linker of natural amino acid. • The in vitro cytotoxicity against three human cell lines and ROS scavenge activities were tested. • Two hybrids (6d and 6f) with well ROS scavenge activities and less cardiotoxicity were identified. Abstract Arenobufagin is a naturally occurring bufadienolide showing promising antitumor activity accompanied however with apparent cardiac toxicity. Following the recent discovery that oxidative damage possibly be an important cause of the cardiac toxicity of cardenolides, a strategy fusing the antitumor agent arenobufagin with a benzoisoselenazol fragment, a reactive oxygen species (ROS) scavenger, has been developed. Six novel hybrids were synthesized and their ROS scavenging activities as well as their in vitro cytotoxicity against the human hepatocellular carcinoma cell line HepG2, an adriamycin-resistant subline HepG2/ADM, and the human myocardial cell line AC16 were evaluated. The results indicate that the hybrids exhibit various degrees of in vitro ROS scavenging activities, and weaker cytotoxicity than that of arenobufagin against the myocardial cell line AC16. These findings suggest the feasibility of a strategy in which the cardiotoxicity of the potential antitumor agent arenobufagin is reduced. [ABSTRACT FROM AUTHOR]

Reactive oxygen (hydroxyl OH, hydroperoxyl OOH) species are highly unstable to be studied experimentally under normal conditions. The present study reports the antioxidant potential of the vitamins namely ascorbic acid, riboflavin and nicotinic acid against these reactive oxygen species (ROS) using the predictive power of Density Functional Theory (DFT) (B3LYP with 6311G basis set) calculations. The order of reactivity of aforementioned vitamins was assessed by determining the bond dissociation enthalpy (BDE) of the OH bond, which is the controlling factor, if hydrogen atom transfer (HAT) mechanism is considered. Transition state calculations were also carried out to determine the reaction barrier for the radical scavenging reaction of vitamins by calculating the forward and the backward activation energies using the same level of theory as mentioned above. The theoretical methodology was first validated by taking a model stable free radical, 2, 2-diphenyl-1, picrylhydrazyl radical (DPPH ) and applying the proposed approach followed by the experimental studies using UV–visible spectroscopy and cyclic voltammetry. The close agreement between the theoretical prediction and experimental observations proved the authenticity of theoretical approach. [ABSTRACT FROM AUTHOR]

Background: Thyroid iodide uptake, mediated by the sodium-iodide symporter (NIS), is essential for thyroid hormone synthesis and also for treatment of thyroid diseases, such as thyroid cancer, through radioiodine therapy. Therefore, compounds able to increase thyroid iodide uptake could be clinically useful, and it is of great importance to unravel the mechanisms underlying such an effect. It has been shown previously that the flavonoid rutin increases thyroid radioiodide uptake in vivo in rats. This study aimed to investigate the mechanisms involved in the stimulatory effect of rutin on iodide uptake. Methods: This study evaluated iodide uptake, NIS expression and its subcellular distribution, iodide efflux, reactive oxygen species levels, and the intracellular pathways involved in NIS regulation in a rat thyroid PCCL3 cell line treated with rutin. Results: Similar to previous results found in vivo, rutin increased radioiodide uptake in PCCL3 cells, which was accompanied by increased NIS expression (at both the mRNA and protein levels) and a reduction of radioiodide efflux. Moreover, the results suggest that rutin could regulate NIS subcellular distribution, leading to higher levels of NIS at the cell membrane. In addition, rutin decreased the levels of intracellular reactive oxygen species and phospho-5'-adenosine monophosphate-activated protein kinase. Conclusions: The flavonoid rutin seems to be an important stimulator of radioiodide uptake, acting at multiple levels, an effect that can be due to decreased oxidative stress, reduced 5′-adenosine monophosphate-activated protein kinase activation, or both. Since thyroid iodide uptake is crucial for effective radioiodine therapy, the results suggest that rutin could be useful as an adjuvant in radioiodine therapy. [ABSTRACT FROM AUTHOR]

Endocrine disruptors are a class of contaminants found in water and process effluents at low concentrations. They are of concern due to their high estrogenic potency. Their presence in the environment has led to the search for effective techniques for their removal in wastewater. For this purpose, an atmospheric air plasma reactor was employed for the study of the degradation of three endocrine disruptor chemicals (EDC) namely; bisphenol A (BPA), estrone (E1) and 17β-estradiol (E2) within a model dairy effluent. Identification of the plasma induced active species both in the gas and liquid phases were performed. Also studied was the influence of an inhibitor, namely tertiary butanol, on the degradation of the EDCs. The results demonstrate that air plasma could successfully degrade the tested EDCs, achieving efficacies of 93% ( k = 0.189 min −1 ) for BPA, 83% ( k = 0.132 min −1 ) for E1 and 86% ( k = 0.149 min −1 ) for E2, with the process following first order kinetics. The removal efficacy was reduced in the presence of a radical scavenger confirming the key role of oxygen radicals such as OH in the degradation process. The intermediate and final products generated in the degradation process were identified using UHPLC-MS and LC-MS. Based on the intermediates identified a proposed degradation pathway is presented. [ABSTRACT FROM AUTHOR]

To date, the mechanisms underlying the flavoprotein l-amino acid oxidase (LAAO) accumulation in cells remain unclear. In this study, using LAAO-producer Pseudoalteromonas spp. as model organisms, we found that the cell biomass is negatively associated with LAAO accumulation, whereas the LAAO accumulation is positively associated with the reactive oxygen species (ROS)-scavenging capability. The expression levels of ROS-scavenging-associated genes were up-regulated with LAAO accumulation in Pseudoalteromonas cells, which is presumably due to the requirement for the removal of LAAO-induced ROS. Exogenous HO exposure experiment supported that the ROS-scavenging system is associated with LAAO accumulation in Pseudoalteromonas. All these observations indicate that ROS-scavenging capacity determines LAAO accumulation in bacterial cells. Our results shed a light on understanding the mechanism underlying controlling and adapting to LAAO accumulation in Pseudoalteromonas. Besides, our findings are critical to the improvement of heterologous expression of active LAAO in the future. [ABSTRACT FROM AUTHOR]

A computational analysis of chemical structures and biomolecular properties of curcumin, the most important component of turmeric, are carried out by means of state-of-the-art methods of calculations. High-level ab initio calculations (G4) along with reliable methods of density functional theory have been used to study all probable mechanisms of curcumin with reactive oxygen species including hydrogen atom transfer, single electron transfer, radical adduct formation and sequential proton loss electron transfer. The calculations have been carried out in solutions of water and n-octanol in order to mimic the role of blood serum and lipid environment in human bodies. Radical stabilization energies are also studied to explore the radical scavenging ability of curcumin and other related derivatives. With the aim of designing more effective species in terms of improved antioxidant activity and solubility, some curcumin-like molecules with different substituents have been also investigated. [ABSTRACT FROM AUTHOR]

The photoprocesses involved in the photo-induced Candida tropicalis biofilm reduction by two natural anthraquinones (AQs), rubiadin (1) and rubiadin-1-methyl ether (2), were examined. Production of singlet oxygen (1O2) and of superoxide radical anion (O2•−) was studied. Although it was not possible to detect the triplet state absorption of any AQs in biofilms, observation of 1O2 phosphorescence incubated with deuterated Phosphate Buffer Solution, indicated that this species is actually formed in biofilms. 2 was accumulated in the biofilm to a greater extent than 1 and produced measurable amounts of O2•− after 3h incubation in biofilms. The effect of reactive oxygen species scavengers on the photo-induced biofilm reduction showed that Tiron (a specific O2•− scavenger) is most effective than sodium azide (a specific 1O2 quencher). This suggests that O2•− formed by electron transfer quenching of the AQs excited states, is the main photosensitizing mechanism involved in the photo-induced antibiofilm activity, whereas 1O2 participation seems of lesser importance. [ABSTRACT FROM AUTHOR]

Magnetic nanoparticles have been demonstrated to produce reactive oxygen species (ROS), which play a major role in various cellular pathways, via Fenton and Haber-Weiss reaction. ROS act as a double-edged sword inside the body. At normal conditions, the generation of ROS is in balance with their elimination by scavenger systems, and they can promote cell proliferation as well as differentiation. However, at an increased level, they can cause damages to protein, lead to cellular apoptosis, and contribute to many diseases including cancer. Many recent studies proposed a variety of strategies to either suppress toxicity of ROS generation or exploit the elevated ROS levels for cancer therapy. [ABSTRACT FROM AUTHOR]

A variety of free radicals (FR)/reactive oxygen species (ROS) have been proposed to dominate methylmercury (MeHg) photodegradation, primarily based on the results of FR/ROS scavenger addition experiments. However, in addition to eliminating FR/ROS, the added scavengers may also affect the experimental results by altering some water chemical properties, resulting in a misleading assessment of the importance of FR/ROS. In this study, 20 common FR/ROS scavengers were evaluated in terms of their influence on light absorbance, pH, MeHg analysis, MeHg-dissolved organic matter (DOM) complexation, and the scavenger-induced degradation of MeHg. Only nine scavengers were identified to be appropriate for investigating MeHg photodegradation. By utilizing these appropriate scavengers, direct photodegradation of MeHg-DOM complexes was found to be the major pathway of MeHg photodegradation in Laoshan Reservoir water and Stone Old Beach seawater. In contrast, MeHg photodegradation in Ink River water primarily occurs through both ·OH and 3DOM* mediated indirect pathways and direct photodegradation of MeHg-DOM complexes. The diverse pathways of MeHg photodegradation in the tested water may be due to differences in water chemical properties. A severe overestimation of the role of FR/ROS was observed when several improper but commonly used scavengers were adopted, highlighting the necessity of utilizing appropriate scavengers. [ABSTRACT FROM AUTHOR]

Macromolecular crystallography (MX) and small-angle X-ray scattering (SAXS) studies on proteins at synchrotron light sources are commonly limited by the structural damage produced by the intense X-ray beam. Several effects, such as aggregation in protein solutions and global and site-specific damage in crystals, reduce the data quality or even introduce artefacts that can result in a biologically misguiding structure. One strategy to reduce these negative effects is the inclusion of an additive in the buffer solution to act as a free radical scavenger. Here the properties of uridine as a scavenger for both SAXS and MX experiments on lysozyme at room temperature are examined. In MX experiments, upon addition of uridine at 1 M, the critical dose D1/2 is increased by a factor of ∼1.7, a value similar to that obtained in the presence of the most commonly used scavengers such as ascorbate and sodium nitrate. Other figures of merit to assess radiation damage show a similar trend. In SAXS experiments, the scavenging effect of 40 m M uridine is similar to that of 5% v/v glycerol, and greater than 2 m M DTT and 1 m M ascorbic acid. In all cases, the protective effect of uridine is proportional to its concentration. [ABSTRACT FROM AUTHOR]

Microbial pathogens often require efficient and robust H2O2 scavenger activities to survive in the presence of reactive oxygen species generated by inflammatory responses. In addition to catalases and peroxidases, enzymes known to scavenge H2O2, a novel class of secreted minicatalases is found in diderm bacteria. Here, we characterize the Helicobacter pylori ( Hp) minicatalase: a monomeric hemoprotein with catalase core homology. Overexpression of Hp minicatalase rescued a catalase/peroxidase-deficient Escherichia coli phenotype under aerobic conditions and limited H2O2 stress. The purified enzyme lacks catalase activity, but has strong ( kcat > 100 s−1) H2O2-dependent peroxidase activity toward a variety of organic substrates. Our investigations into heme binding revealed that the heme cofactor is assembled in the periplasm to form the functional holoprotein. Furthermore, we observed the presence of a disulfide bond near the heme cavity of Hp minicatalase, which is conserved in secreted minicatalases and, therefore, may play a role in heme binding. [ABSTRACT FROM AUTHOR]

Recently, hydropersulfide (RSSH) was found to exist in mammalian tissues and fluids. Cysteine hydropersulfide can be found in free cysteine residues as well as in proteins, and it has potent antioxidative activity. Human serum albumin (HSA) is the most abundant protein in mammalian serum. HSA possesses a free thiol group in Cys-34 that could be a site for hydropersulfide formation. HSA hydropersulfide of high purity as a positive control was prepared by treatment of HSA with Na 2 S. The presence of HSA hydropersulfide was confirmed by spectroscopy and ESI-TOFMS analysis where molecular weights of HSA hydropersulfide by increments of approximately 32 Da (Sulfur atom) were detected. The fluorescent probe results showed that Alexa Fluor 680 conjugated maleimide (Red-Mal) was a suitable assay and bromotrimethylammoniumbimane bromide appeared to be a selective reagent for hydropersulfide. The effect of oxidative stress related disease on the existence of albumin hydropersulfides was examined in rat 5/6 nephrectomy model of chronic kidney disease (CKD). Interestingly, the level of hydropersulfides in rat 5/6 nephrectomy model serum was decreased by a uremic toxin that increases oxidative stress in rat 5/6 nephrectomy model. Furthermore, we demonstrated that the levels of HSA hydropersulfide in human subjects were reduced in CKD but restored by hemodialysis using Red-Mal assay. We conclude that HSA hydropersulfide could potentially play an important role in biological anti-oxidative defense, and it is a promising diagnostic and therapeutic marker of oxidative diseases. [ABSTRACT FROM AUTHOR]

New polyhydroxylated flavon-3-ols and 3-hydroxy-2-styrylchromones were prepared and assessed as reactive oxygen species (ROS) and reactive nitrogen species (RNS) scavengers. The synthetic strategy involved the preparation of 2′-hydroxychalcones and 2′-hydroxycinnamylidenoacetophenones from base-catalyzed aldol reaction of appropriate 2′-hydroxyacetophenones and benzaldehydes/cinnamaldehydes, followed by an Algar-Flynn-Oyamada (AFO) reaction to give the polyalkoxy(flavon-3-ols and 3-hydroxy-2-styrylchromones). The last step of this synthetic route consisted in the cleavage of the protecting groups affording the expected polyhydroxylated derivatives. The present work consisted in the study of the in vitro scavenging activities of the synthetized compounds against the most physiologically relevant ROS [superoxide radical (O 2 - ), hydrogen peroxide (H 2 O 2 ), hypochlorous acid (HOCl), singlet oxygen ( 1 O 2 ) and peroxyl radical (ROO )] and RNS [nitric oxide ( NO) and peroxynitrite anion (ONOO − )]. Generally, all the tested new polyhydroxylated flavon-3-ols and 3-hydroxy-2-styrylchromones exhibited scavenging effects dependent on the concentration, and with IC 50 values found within the micromolar range. This work allowed the establishment of new structure-activity relationships and brought the knowledge about the selective choice of a structure depending on the targeted reactive species. [ABSTRACT FROM AUTHOR]

In this study, we report on the potential use of platinum nanoparticles (Pt-NPs), a superoxide dismutase (SOD)/catalase mimetic antioxidant, in combination with 1 MHz ultrasound (US) at an intensity of 0.4 W/cm 2 , 10% duty factor, 100 Hz PRF, for 2 min. Apoptosis induction was assessed by DNA fragmentation assay, cell cycle analysis and Annexin V-FITC/PI staining. Cell killing was confirmed by cell counting and microscopic examination. The mitochondrial and Ca 2+ -dependent pathways were investigated. Caspase-8 expression and autophagy-related proteins were detected by spectrophotometry and western blot analysis, respectively. Intracellular reactive oxygen species (ROS) elevation was detected by flow cytometry, while extracellular free radical formation was assessed by electron paramagnetic resonance spin trapping spectrometry. The results showed that Pt-NPs exerted differential effects depending on their internalization. Pt-NPs functioned as potent free radical scavengers when added immediately before sonication while pre-treatment with Pt-NPs suppressed the induction of apoptosis as well as autophagy (AP), and resulted in enhanced cell killing. Dead cells displayed the features of pyknosis. The exact mode of cell death is still unclear. In conclusion, the results indicate that US-induced AP may contribute to cell survival post sonication. To our knowledge this is the first study to discuss autophagy as a pro-survival pathway in the context of US. The combination of Pt-NPs and US might be effective in cancer eradication. [ABSTRACT FROM AUTHOR]

Promising applications of metal-organic frameworks (MOFs) in various fields have raised concern over their environmental fate and safety upon inevitable discharge into aqueous environments. Currently, no information regarding the transformation processes of MOFs is available. Due to the presence of repetitive π-bond structure and semiconductive property, photochemical transformations are an important fate process that affects the performance of MOFs in practical applications. In the current study, the generation of reactive oxygen species (ROS) in isoreticular MIL-53s was studied. Scavengers were employed to probe the production of ¹O2, O2•-, and •OH, respectively. In general, MIL-53(Cr) and MLL-53(Fe) are dominated by type I and II photosensitization reactions, respectively, and MIL-53(A1) appears to be less photo reactive. The generation of ROS in MIL-53(Fe) may be underestimated due to dismutation. Further investigation of MIL-$3(Fe) encapsulated diclofenac transformation revealed that diclofenac can be easily transformed by MIL-53(Fe) generated ROS. However, the cytotoxicity results implied that the ROS generated from MIL-53s have little effect on the viability of the human hepatocyte (HepG2) cell line. These results suggest that the photogeneration of ROS by MOFs may be metal-node dependent, and the application of MIL-53s as drug carriers needs to be carefully considered due to their high photoreactivity. [ABSTRACT FROM AUTHOR]

Abstract: In the present work, cerium oxide (CeO2)‐based nanocomposites integrating fluorescent carbon dots (CDs) were synthesized by a hydrothermal method. The formation and cellular uptake of these nanocomposites was studied by various analytical techniques. The therapeutic and imaging aspects of CDs‐CeO2 nanocomposites were validated using NIH3T3 fibroblast cells as a model system. The antioxidant potency of CDs‐CeO2 nanocomposites was also evaluated in cells treated with H2O2, a major reactive oxygen species (ROS) species, using a 2′,7′‐dichlorofluorescin diacetate (DCFH‐DA) assay. Tracking the intracellular fluorescence of CDs‐CeO2 nanocomposites by microscopy and flow cytometry made it possible to examine the capabilities of CeO2 for abatement of H2O2‐mediated oxidative stress. Taken together, the present study motivates the use of therapeutic nanocomposites whilst monitoring their uptake, which holds clinical relevance for ROS‐related diseases. [ABSTRACT FROM AUTHOR]

A series of Ca-doped bismuth ferrite was prepared at various %w/w of Ca via a facile hydrothermal method to obtain Bi 2X Ca 2(1-X) Fe 4 O 9 (denoted as BFOCa-X, where X = 1, 0.95, 0.90, 0.80, 0.50). The BFOCa-X catalysts were characterized, and the results showed that they consist of pure phase BFO with nanosheet-like morphology. The as-prepared BFOCa-X catalysts were used as peroxymonosulfate (PMS) activator for gatifloxacin (GAT) removal. It was found that the catalytic activity decreased in the following order: BFOCa-0.8 (90.2% GAT removal efficiency in 45 min, k app = 0.084 min−1)>BFOCa-0.95 > BFOCa-0.9 > BFOCa-0.5 > BFO indicating that BFOCa-0.8 has the optimized active sites for catalysis. The Ca dopant contributed to the increased oxygen vacancies and surface hydroxyl groups, promoting the catalytic PMS activation process. The k app value increased gradually with increasing catalyst loading and PMS dosage while pH 9 presented the highest GAT removal rate. The GAT degradation rate was inhibited by PO 4 3ˉ, humic acid and NH 4 + but promoted in the presence of Clˉ, NO 3 ˉ and HCO 3 ˉ. It was also found that the GAT can undergo several degradation pathways in the catalytic PMS system, which eventually mineralized into innocuous compounds. The dominant reactive oxygen species (ROS) were identified using chemical scavengers, revealing that SO 4 •ˉ, 1O 2 and •OH contributed significantly to GAT degradation. Based on the XPS study, PMS was activated by the Fe2+/Fe3+ redox cycling and oxygen vacancies to produce SO 4 •ˉ/•OH and 1O 2 , respectively. Overall, the BFOCa-0.8 also showed excellent reusability up to at least 4 cycles with low Bi and Fe leaching (<7 and 62 μg L−1, respectively), indicating that it has promising potential for application as PMS activator for antibiotics removal. [Display omitted] • Ca-doped bismuth ferrite (BFOCa) was prepared hydrothermally and characterized. • Ca doping induced the formation of oxygen vacancies in BFO to promote catalytic activity. • BFOCa can effectively activate peroxymonosulfate (PMS) to degrade gatifloxacin (GAT). • BFOCa activated PMS to produce SO 4.•ˉ, 1O 2 and •OH for GAT degradation. • The degradation pathways of GAT were proposed based on the intermediates identified. [ABSTRACT FROM AUTHOR]

A comparative study of visible-light-responsive Bi2WO6 and oxygen-deficient Bi2WO6-x nanoplates was conducted. The formation of oxygen vacancy resulted in the band gap narrowing of oxygen-deficient Bi2WO6-x, through an elevation of both of the conduction and valence band positions. FTIR spectra revealed that much more surface hydroxyl groups have been detected after the etching process. The scavengers tests confirmed the generation of ·OH radicals during photochemical reaction for Bi2WO6-x, whereas no COH radicals can be detected for pure Bi2WO6. The photocatalytic activities of optimized Bi2WO6-x on the decomposition of Rhodamine B (RhB) was three times as high as that of pure Bi2WO6. The improvement of photocatalytic activity on degradation of RhB and phenol can be ascribed to the synergistic effect of oxygen deficiencyinduced band shifts, together with the large quantities of surface hydroxyl groups providing active sites for the generation of OH radicals (COH). [ABSTRACT FROM AUTHOR]

The profusely employed drugs Piroxicam (Piro), Tenoxicam (Teno) and Meloxicam (Melo) belonging to the non-steroidal antiinflammatory drug (NSAID) family of the Oxicams (Oxis) were studied in the frame of two specific conditions: (a) their ROS scavenging ability, in relation to a possible biological antioxidant action and (b) their photodegradability under environmental conditions, in the context of Oxi-contaminated waters. Singlet molecular oxygen (O 2 ( 1 Δ g )) and superoxide radical anion (O 2 − ) were photogenerated through Riboflavin (Rf, vitamin B2)-photosensitization in aqueous and aqueous-methanolic solutions in the presence of Oxi concentrations in the range 50–500 μM. The visible-light absorber vitamin is currently present in all types of natural waters and constitutes the most frequent endogenous photosensitizer in mammals. Hence, it was employed in order to mimic both natural sceneries of interest. All three Oxis quench O 2 ( 1 Δ g ) with rate constants in the order of 10 8 M − 1 s − 1 showing a significant photodegradation efficiency given by a dominant reactive fashion for deactivation of the oxidative species. Although this is not a desirable property in the context of photoprotection upon prolonged photoirradiation, constitutes in fact a promissory aspect for the degradation NSAIDs, in waste waters. Indirect evidence indicates that Melo is also oxidized through a O 2 − -mediated component. The simultaneous presence of Piro plus tryptophan or tyrosine under Rf-photosensitizing conditions, which has taken the amino acids as photooxidizable model residues in a proteinaceous environment, indicates that the NSAID induces a protection of the biomolecules against photodynamic degradation. [ABSTRACT FROM AUTHOR]

Etching of gold with an excess of thiol ligand is used in both synthesis and analysis of gold particles. Mechanistically, the process of etching gold with excess thiol is unclear. Previous studies have obliquely considered the role of oxygen in thiolate etching of gold. Herein, we show that oxygen or a radical initiator is a necessary component for efficient etching of gold by thiolates. Attenuation of the etching process by radical scavengers in the presence of oxygen, and the restoration of activity by radical initiators under inert atmosphere, strongly implicate the oxygen radical. These data led us to propose an atomistic mechanism in which the oxygen radical initiates the etching process. [ABSTRACT FROM AUTHOR]

Resveratrol monomer ( Res ) and its oligomers are considered as nutritional components distributed in edible plants. Three naturally occurring resveratrol dimers, namely parthenocissin A ( Par ), quadrangularin A ( Qua ) and pallidol ( Pal ), were synthesized and evaluated for their ability to scavenge reactive oxygen species (ROS) and to activate the transcription factor Nrf2, which regulates cellular antioxidant systems. In vitro studies with different ROS and radical assay models showed that all the three dimers are strong DPPH quenchers and selective singlet oxygen ( 1 O 2 ) scavengers (IC 50 = 4.90, 1.05 and 5.50 μM, respectively). However, they were ineffective against hydroxyl radical ( OH) or superoxide anion (O 2 − ). Exposing the dimers to an antioxidant response element (ARE) reporter cell line revealed that only pallidol was able to activate Nrf2 at 30 μM, while parthenocissin A and quadrangularin A had no significant effect on Nrf2. Our data demonstrates the distinct difference between reservatrol monomer and its dimers in activating the Nrf2/ARE signalling pathway. [ABSTRACT FROM AUTHOR]

We report the effects of zeolite pore systems in limiting the oxidation of ascorbic acid (vitamin C) in plasma using the mixing of FeCl 2 and H 2 O 2 (“Fenton solution”) as an oxidant. We tested three homemade zeolites and nineteen natural zeolites. Six polar zeolites were effective in restricting the oxidation of vitamin C and the majority of them acted by chelation of ferrous/ferric chloride. Faujasite (FAU 13x ) was the most active ROS scavenger. On the other hand, two natural zeolites, Goosecreekite and Stilbite (GOO nat and STI nat ), inhibited the oxidation of vitamin C by action on the reduction of hydrogen peroxide concentration to form H 2 O. Our hypothesis suggests that effective zeolites have the advantage of never being saturated in the time. Here, for the first time, we identified a substrate (zeolite) which acts directly on the two substrates (Fe 2+ /H 2 O 2 ) to limit ROS formation. [ABSTRACT FROM AUTHOR]

• A new method to degrade SDZ based on trace Cu2+ and calcite is proposed. • The degradation can be carried out over a wide range of pH values. • The Cu(Ⅲ) is proved to dominate the SDZ degradation. • The complex of Cu-CO 3 is the main activate site for Cu(Ⅲ) generation. A system of Cu2+/calcite/PDS was constructed to degrade sulfadiazine (SDZ). Different from the traditional Cu-mediated activation, a low concentration of Cu2+ that met drinking water standards (≤ 1 mg/L) transformed into Cu(Ⅱ) solid in the presence of calcite, and then enhanced the degradation of SDZ via PDS activation over a pH range from 3 to 9. According to scavenger and chemical probe experiments, Cu(Ⅲ), rather than radicals (hydroxyl radicals and sulfate radicals) and singlet oxygen, was the predominant reactive species, which was responsible for the degradation of SDZ. Based on the results of XRD, ATR-FTIR, and CV curves et al., CuCO 3 was the main complex with high reactivity for PDS activation to form Cu(Ⅲ). Moreover, detailed degradation pathways of sulfadiazine were proposed according to the UPLC-ESI-MS/MS and their toxicity was predicted by ECOSAR. Besides, the real water matrix would not seriously affect the degradation of SDZ in the Cu2+/calcite/PDS system. In summary, this study reveals a new insight into the synergistic effect of Cu2+ and calcite on the SDZ degradation, and promotes an understanding of the environmental benefits of natural calcite. [Display omitted] [ABSTRACT FROM AUTHOR]

A hydrophilic extract of murici ( Byrsonima crassifolia ), a fruit native to the North and Northeast regions of Brazil, was evaluated in relation to its phenolic composition and in vitro antioxidant potential against some physiologically relevant reactive oxygen and nitrogen species. Additionally, the protective effect of murici extract against peroxyl radical (ROO )-induced toxicity to human erythrocytes was also determined. The major phenolic compound, determined by HPLC–DAD–MS n , was quercetin (2.72 ± 0.35 μg/mL). The extract was able to scavenge ROO (0.30 ± 0.04 μmol trolox equivalent/mg), hypochlorous acid (IC 50 = 10.0 ± 0.1 μg/mL), hydroxyl radical (IC 50 = 7 ± 1 μg/mL) and peroxynitrite anion (IC 50 = 21.0 ± 0.6 μg/mL and 17.0 ± 1.6 μg/mL, respectively, in absence and presence of NaHCO 3 ). Human erythrocytes were subjected to oxidative damage, but murici extract was not able to inhibit hemolysis, even at the highest tested concentration. On the other hand, the extract inhibited hemoglobin oxidation (IC 50 = 271 ± 44 μg/mL), lipid peroxidation (1000 μg/mL) by 48 ± 5%, depletion of glutathione (100 μg/mL) by 49 ± 2% and formation of its oxidized form (100 μg/mL) by 96 ± 4%. [ABSTRACT FROM AUTHOR]

The globe artichoke ( Cynara cardunculus L. subsp. cardunculus ) is a perennial plant cultivated in the Mediterranean region and Americas for its edible young flower heads and as an interesting source of bioactive compounds. The present study was undertaken to evaluate scavenging capacity against the most physiologically relevant reactive oxygen species (ROS) and reactive nitrogen species (RNS) of three different extracts from artichoke leaves (infusion, decoction and hydroalcoholic) using different solvents, commonly accepted for human consumption (water and a mixture of ethanol/water). Additionally, the phenolic compounds in each extract were identified and quantified by high performance liquid chromatography coupled to diode array and mass spectrometer detectors (HPLC–DAD–MS/MS). Chlorogenic acid was the major phenolic compound identified in all extracts, followed by 1,3-dicaffeoylquinic acid (cynarin), luteolin-7-rutinoside and the infusion extract presented the highest phenolic content (108 mg/g extract, dry basis). In general, the extracts of artichoke leaves presented a remarkable capacity to scavenge ROS and RNS with IC 50 values in a low μg/mL range (3.4–43 μg/mL). These findings suggest that artichoke could be a potential source of natural antioxidants and has an undeniable nutraceutical value. [ABSTRACT FROM AUTHOR]

Key message: The antioxidant system was significantly inhibited in the early aging line than the near-isogenic normal aging line during senescence. Abstract: The antioxidant system plays pivotal roles in removal of reactive oxygen species (ROS) produced during leaf senescence. To explore its roles in leaf senescence of wheat ( Triticum aestivum L.), the concentrations of antioxidants, activities, and gene expression of antioxidant enzymes were evaluated in flag leaves of the early aging line (EAL) and the near-isogenic normal aging line (NL) during senescence. The results showed that the total chlorophyll and soluble protein in the EAL declined earlier and faster, while more malondialdehyde and ROS accumulated compared with the NL. The activities of superoxide dismutase, catalase, ascorbate peroxidase, dehydroascorbate reductase, and glutathione reductase were lower in the EAL than in the NL across multiple measuring dates. Additionally, the EAL had less amounts of reduced ascorbate and glutathione as well as lower reduction state with the progression of senescence. Concomitantly, the gene expression of antioxidant enzymes in the EAL was also significantly repressed relative to those in the NL during natural senescence. Taken together, the earlier onset and faster rate of senescence in the EAL could be a result of an imbalance of ROS production and ROS-scavenging antioxidant system, which provided valuable hints toward understanding leaf senescence of wheat. [ABSTRACT FROM AUTHOR]

Background and Aims The addition of oenological tannins during winemaking is a longstanding technological practice. To assist such a practice, knowledge of their antioxidant properties is an asset for understanding their role in redox processes occurring in wine. Hence, the aim of this work was to assess the antioxidant profile of oenological tannins from several botanical sources, which are usually applied at different winemaking steps. Methods and Results Several antioxidant assays, including the ability to reduce copper( II) assay (CUPRAC), the scavenging capacity against 2,2′-azinobis-(3-ethylbenzothiazoline-6-sulfonate) (ABTS) and 2,2-diphenyl-1-picrylhydrazyl radicals (DPPH), and the peroxyl radical scavenging capacity (oxygen radical absorbance capacity assay, ORAC) were applied. The concentration of phenolic substances and the ability to chelate iron( II) (ICA) were also determined. A significant correlation was obtained between the concentration of phenolic substances and the copper(II) reducing antioxidant capacity ( R = 0.89), and the 2,2′-azinobis-(3-ethylbenzothiazoline-6-sulfonate) ( R = 0.86) and 2,2-diphenyl-1-picrylhydrazyl ( R = 0.86) assays. No such correlation was observed ( R = 0.15) with the oxygen radical absorbance capacity assay. Conclusions The highest radical scavenging capacity was attained for oenological tannins composed of gallotannins, while those containing ellagic acid were able to chelate iron( II) strongly, preventing the oxidative damage mediated by Fenton-based reactions. Condensed tannins demonstrated a significant ability to scavenge peroxyl radicals, which represents a powerful antioxidant mechanism to prevent lipid peroxidation. Significance of the Study The chemical antioxidant profile of oenological tannins displayed in radar charts provides valuable information for winemakers and manufacturers of oenological tannins. [ABSTRACT FROM AUTHOR]

We investigated the photo-protective effect of sugar-based surfactants-hexyl glucoside and hexyl maltoside-against light-induced oxidation of a monoclonal antibody. Reactive oxygen species are generated in solutions in the presence of light; these reactive species readily oxidize amino acids such as tryptophan. Hexyl glucosides and hexyl maltosides scavenge these reactive species and protect tryptophan residues from light-induced oxidation in a concentration-dependent manner. As a result of the scavenging process, hydrogen peroxide is formed, especially at high (millimolar) concentrations of the alkyl glycoside surfactants. These results suggest that hexyl glucoside and hexyl maltoside have the potential to protect tryptophan residues against light-induced oxidation. © 2013 Wiley Periodicals, Inc. and the American Pharmacists Association J Pharm Sci 103:409-416, 2014 [ABSTRACT FROM AUTHOR]

Theaccumulation of proline (Pro) and overproductionof reactive oxygen species (ROS) by plants exposed to stress is well-documented.In vitro assays show that enzyme inactivation by hydroxyl radicals(•OH) can be avoided in the presenceof Pro, suggesting this amino acid might act as a •OH scavenger. Although production of hydroxyproline(Hyp) has been hypothesized in connection with such antioxidantactivity, no evidence on the detailed mechanism of scavenging hasbeen reported. To elucidate whether and how Hypmightbe produced, we used density functional theory calculations coupledto a polarizable continuum model to explore 27 reaction channels includingH-abstraction by •OH and •OH/H2O addition. The structure andenergetics of stable species and transition states for each reactionchannel were characterized at the PCM-(U)M06/6-31G(d,p) level in aqueoussolution. Evidence is found for a main pathway in which Proscavenges •OH by successive H-abstractions(ΔG⧧,298= 4.1 and 7.5 kcal mol–1) to yield 3,4-Δ-Pro. A companionpathway with low barriers yielding Δ1-pyrroline-5-carboxylate(P5C) is also supported, linking with 5-Hypthrough hydration. However, this connection remainsunlikely in stressed plants because P5Cwould be efficientlyrecycled to Pro(contributing to its accumulation) by P5Creductase, hypothesis coined here as the “Pro-Procycle”. [ABSTRACT FROM AUTHOR]

• Cu-rGO LDH nanohybrid fabricated by intercalating rGO inside the LDH galleries. • Cu-rGO LDH exhibited higher surface area and electrical conductivity. • Cu-rGO LDH/PMS induced nonradical pathway. • 1O 2 generated through SO 5 − owing to electron conduction between PMS and Cu2+. A new strategy was applied by periodic stacking of active sites of Cu and reduced graphene oxide (rGO) in the form of Cu-rGO LDH nanohybrid material. The experimental results revealed that newly prepared Cu-rGO LDH nanohybrid material was extremely reactive in PMS activation as evident from the degradation rate of 0.115 min−1, much higher than Mn-rGO LDH (0.071 min−1), Zn-rGO LDH (0.023 min−1) or other benchmarked material used during the degradation of bisphenol A (BPA). This excellent activity of Cu-rGO LDH nanohybrid was attributed to the better PMS utilization efficiency as compared to the other catalysts. Additionally, the characterization techniques disclosed that the layer by layer arrangement of active sites in the Cu-rGO LDH catalyst promotes interfacial electron mobility owing to the synergistic association between Cu in LDH and interlayered rGO. Based on the in-situ electron paramagnetic resonance spectroscopy (EPR) and chemical scavengers, singlet oxygen (1O 2) was unveiled as dominant reactive species for pollutant removal, resulting from the recombination of superoxides (O 2 −) or reduction of active Cu centers. We believe that this novel Cu-rGO LDH/PMS system will open up a new avenue to design efficient metal-carbon nanohybrid catalysts for the degradation of emerging aquatic pollutants in a real application. [ABSTRACT FROM AUTHOR]