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Oxidative Medicine and Cellular... 2020Free radicals are chemical species (atoms, molecules, or ions) containing one or more unpaired electrons in their external orbitals and generally display a remarkable... (Review)
Review
Free radicals are chemical species (atoms, molecules, or ions) containing one or more unpaired electrons in their external orbitals and generally display a remarkable reactivity. The evidence of their existence was obtained only at the beginning of the 20th century. Chemists gradually ascertained the involvement of free radicals in organic reactions and, in the middle of the 20th century, their production in biological systems. For several decades, free radicals were thought to cause exclusively damaging effects . This idea was mainly supported by the finding that oxygen free radicals readily react with all biological macromolecules inducing their oxidative modification and loss of function. Moreover, evidence was obtained that when, in the living organism, free radicals are not neutralized by systems of biochemical defences, many pathological conditions develop. However, after some time, it became clear that the living systems not only had adapted to the coexistence with free radicals but also developed methods to turn these toxic substances to their advantage by using them in critical physiological processes. Therefore, free radicals play a dual role in living systems: they are toxic by-products of aerobic metabolism, causing oxidative damage and tissue dysfunction, and serve as molecular signals activating beneficial stress responses. This discovery also changed the way we consider antioxidants. Their use is usually regarded as helpful to counteract the damaging effects of free radicals but sometimes is harmful as it can block adaptive responses induced by low levels of radicals.
Topics: Animals; Antioxidants; Free Radicals; Humans; Oxidants; Oxidative Stress; Reactive Oxygen Species; Superoxide Dismutase
PubMed: 32411336
DOI: 10.1155/2020/9829176 -
Journal of Esthetic and Restorative... Sep 2019The aim is to review the most important aspects about tooth whitening treatments, their side effects, and the new emerging approaches to overcome them. (Review)
Review
OBJECTIVE
The aim is to review the most important aspects about tooth whitening treatments, their side effects, and the new emerging approaches to overcome them.
OVERVIEW
This review is focused on origin of tooth stains, the whitening systems and their chemistry, their side effects, and the new approaches. The search of bibliography of the period 1965-2018 has been analyzed.
CONCLUSIONS
Tooth whitening has become one of the most requested dental treatments by the public. Tooth stains are classified according to their origin into two categories: intrinsic and extrinsic. The whitening systems are generally organized into two classes: in-office and at-home products. Most of the whitening systems use hydrogen peroxide as the active oxidative agent to degrade the organic compounds that cause stains. The concentration ranges depending on the treatment, and it may be applied directly or produced in a chemical reaction from carbamide peroxide that is more stable. Besides its popularity, tooth whitening still has some side effects being tooth hypersensitivity the most common. In order to decrease these side effects, new treatments are constantly in renewal processes.
CLINICAL SIGNIFICANCE
Despite all the data and new strategies known about tooth whitening, there are many aspects that are not totally fully understood and methodologies that are not completely effective. Therefore, the development of effective, efficient, and long-lasting whitening treatments is still necessary.
Topics: Drug Combinations; Hydrogen Peroxide; Peroxides; Tooth Bleaching; Tooth Bleaching Agents; Urea
PubMed: 31448534
DOI: 10.1111/jerd.12519 -
Water Research Apr 2024This publication summarizes my journey in the field of chemical oxidation processes for water treatment over the last 30+ years. Initially, the efficiency of the... (Review)
Review
This publication summarizes my journey in the field of chemical oxidation processes for water treatment over the last 30+ years. Initially, the efficiency of the application of chemical oxidants for micropollutant abatement was assessed by the abatement of the target compounds only. This is controlled by reaction kinetics and therefore, second-order rate constant for these reactions are the pre-requisite to assess the efficiency and feasibility of such processes. Due to the tremendous efforts in this area, we currently have a good experimental data base for second-order rate constants for many chemical oxidants, including radicals. Based on this, predictions can be made for compounds without experimental data with Quantitative Structure Activity Relationships with Hammet/Taft constants or energies of highest occupied molecular orbitals from quantum chemical computations. Chemical oxidation in water treatment has to be economically feasible and therefore, the extent of transformation of micropollutants is often limited and mineralization of target compounds cannot be achieved under realistic conditions. The formation of transformation products from the reactions of the target compounds with chemical oxidants is inherent to oxidation processes and the following questions have evolved over the years: Are the formed transformation products biologically less active than the target compounds? Is there a new toxicity associated with transformation products? Are transformation products more biodegradable than the corresponding target compounds? In addition to the positive effects on water quality related to abatement of micropollutants, chemical oxidants react mainly with water matrix components such as the dissolved organic matter (DOM), bromide and iodide. As a matter of fact, the fraction of oxidants consumed by the DOM is typically > 99%, which makes such processes inherently inefficient. The consequences are loss of oxidation capacity and the formation of organic and inorganic disinfection byproducts also involving bromide and iodide, which can be oxidized to reactive bromine and iodine with their ensuing reactions with DOM. Overall, it has turned out in the last three decades, that chemical oxidation processes are complex to understand and to manage. However, the tremendous research efforts have led to a good understanding of the underlying processes and allow a widespread and optimized application of such processes in water treatment practice such as drinking water, municipal and industrial wastewater and water reuse systems.
Topics: Bromides; Iodides; Water Pollutants, Chemical; Oxidation-Reduction; Oxidants; Water Purification
PubMed: 38387263
DOI: 10.1016/j.watres.2024.121148 -
Molecules (Basel, Switzerland) Jul 2023The chemistry of hypervalent iodine reagents has now become quite valuable due to the reactivity of these compounds under mild reaction conditions and their resemblance... (Review)
Review
The chemistry of hypervalent iodine reagents has now become quite valuable due to the reactivity of these compounds under mild reaction conditions and their resemblance in chemical properties to transition metals. The environmentally friendly nature of these reagents makes them suitable for Green Chemistry. Reagents with a dual nature, such as iodine(III) reagents, are capable electrophiles, while iodine(V) reagents are known for their strong oxidant behavior. Various iodine(V) reagents including IBX and DMP have been used as oxidants in organic synthesis either in stoichiometric or in catalytic amounts. In this review article, we describe various oxidation reactions induced by iodine(V) reagents reported in the past decade.
Topics: Iodine; Oxidants; Oxidation-Reduction; Indicators and Reagents; Catalysis
PubMed: 37446912
DOI: 10.3390/molecules28135250 -
Current Organic Synthesis 2022Organoselenium chemistry has developed as an important tool in the field of synthetic and medicinal chemistry. Various organoselenium reagents have been developed and... (Review)
Review
Organoselenium chemistry has developed as an important tool in the field of synthetic and medicinal chemistry. Various organoselenium reagents have been developed and used successfully to achieve different organic transformations such as selenocyclizations, oxyselenenylations, selenoxide eliminations, etc. Additionally, organoselenium reagents' potential is not limited to their use as stoichiometric reagents, but they have been successfully used as organocatalysts in a number of synthetic transformations. Various organic and inorganic oxidants have been identified as terminal oxidants to regenerate the active catalytic species. In this review article, the recent progress of organoselenium reagents in catalysis is being highlighted along with their asymmetric variants.
Topics: Catalysis; Indicators and Reagents; Oxidants; Oxidation-Reduction; Selenium Compounds
PubMed: 35152866
DOI: 10.2174/1570179419666220211102602 -
Chemosphere Jul 2016Preoxidation has attracted people's attention due to its effectiveness in enhancing coagulation. The mechanisms, drawbacks and applications in the improvement of... (Review)
Review
Preoxidation has attracted people's attention due to its effectiveness in enhancing coagulation. The mechanisms, drawbacks and applications in the improvement of coagulation were summarized in this work. Preoxidation can destroy the organic coating on the surface of particles to change the zeta potential, which is the vital reason for improving coagulation. Co-existing metallic ions, such as calcium, iron and manganese, play important roles in the improvement of coagulation due to the formation of metal-humate complexes or the in situ formed coagulant. However, preoxidation could degrade organic matter from high molecular weight to low molecular weight and damage cell membrane of algae, causing intracellular algal organic matter to release outside and producing hydrophilic functional groups to some extent, which has the potential to deteriorate the water quality. Additionally, disinfection byproduct formation is also affected significantly through changing the characteristics of the organic and inorganic precursors. Based on the recent publications, some future developments of preoxidation process were suggested in this study.
Topics: Colloids; Disinfection; Drinking Water; Electric Conductivity; Eutrophication; Metals; Oxidants; Oxidation-Reduction; Particulate Matter; Water Purification; Water Quality
PubMed: 27153238
DOI: 10.1016/j.chemosphere.2016.04.003 -
Environmental Science & Technology Apr 2023Methylmercury (MeHg) is a potent neurotoxin and has great adverse health impacts on humans. Organisms and sunlight-mediated demethylation are well-known detoxification...
Methylmercury (MeHg) is a potent neurotoxin and has great adverse health impacts on humans. Organisms and sunlight-mediated demethylation are well-known detoxification pathways of MeHg, yet whether abiotic environmental components contribute to MeHg degradation remains poorly known. Here, we report that MeHg can be degraded by trivalent manganese (Mn(III)), a naturally occurring and widespread oxidant. We found that 28 ± 4% MeHg could be degraded by Mn(III) located on synthesized Mn dioxide (MnO) surfaces during the reaction of 0.91 μg·L MeHg and 5 g·L mineral at an initial pH of 6.0 for 12 h in 10 mM NaNO at 25 °C. The presence of low-molecular-weight organic acids (e.g., oxalate and citrate) substantially enhances MeHg degradation by MnO via the formation of soluble Mn(III)-ligand complexes, leading to the cleavage of the carbon-Hg bond. MeHg can also be degraded by reactions with Mn(III)-pyrophosphate complexes, with apparent degradation rate constants comparable to those by biotic and photolytic degradation. Thiol ligands (cysteine and glutathione) show negligible effects on MeHg demethylation by Mn(III). This research demonstrates potential roles of Mn(III) in degrading MeHg in natural environments, which may be further explored for remediating heavily polluted soils and engineered systems containing MeHg.
Topics: Humans; Manganese; Methylmercury Compounds; Mercury; Oxidants; Cysteine
PubMed: 36995950
DOI: 10.1021/acs.est.3c00532 -
Chemistry (Weinheim An Der Bergstrasse,... Aug 2023Steroids are highly prevalent structures in small-molecule therapeutics, with the level of oxidation being key to their biological activity and physicochemical... (Review)
Review
Steroids are highly prevalent structures in small-molecule therapeutics, with the level of oxidation being key to their biological activity and physicochemical properties. These C(sp )-rich tetracycles contain many stereocentres, which are important for creating specific vectors and protein binding orientations. Therefore, the ability to hydroxylate steroids with a high degree of regio-, chemo- and stereoselectivity is essential for researchers working in this field. This review will cover three main methods for the hydroxylation of steroidal C(sp )-H bonds: biocatalysis, metal-catalysed C-H hydroxylation and organic oxidants, such as dioxiranes and oxaziridines.
Topics: Hydroxylation; Oxidation-Reduction; Oxidants; Steroids; Biocatalysis
PubMed: 37235530
DOI: 10.1002/chem.202301066 -
Australian Dental Journal Jun 2023Intracoronal bleaching is a minimally invasive procedure that was introduced into dentistry in the 19th century. The role of that procedure in enhancing the colour of... (Review)
Review
Intracoronal bleaching is a minimally invasive procedure that was introduced into dentistry in the 19th century. The role of that procedure in enhancing the colour of teeth subjected to internal discolouration while being conservative made it extremely popular amongst dental professionals. Different materials and techniques have been utilized over the years attempting to obtain predictable long-term results while minimizing any associated risks. Contemporarily, bleaching agents are mainly based on peroxide-releasing compounds in different formulations and delivery systems. Different theories have been formulated on the bleaching mechanism of such agents, but the exact mechanism is yet to be proven. The effect of hydrogen peroxide-based bleaching agents on the organic structure of enamel and dentine has been extensively investigated to address the effects of bonding of resin-based restorative materials to hard tooth structure. Multiple case reports raised a concern about the contribution of intracoronal bleaching in developing invasive root resorption. Modification of intracoronal bleaching techniques was thus necessary to address such concerns. This review will provide a summary of the important aspects of intracoronal bleaching, focusing on how it applies to the contemporary clinical setting. © 2023 Australian Dental Association.
Topics: Humans; Tooth Bleaching; Borates; Australia; Hydrogen Peroxide; Bleaching Agents
PubMed: 37975331
DOI: 10.1111/adj.13000 -
Archives of Microbiology Sep 2020The aim is to evaluate the prooxidant and antimicrobial effects of FeO and TiO nanoparticles and thalicarpine by luminescent and standard microbiological assays. Their...
The aim is to evaluate the prooxidant and antimicrobial effects of FeO and TiO nanoparticles and thalicarpine by luminescent and standard microbiological assays. Their effect on the kinetics of free-radical oxidation reactions (at pH 7.4 and pH 8.5) is studied in the following model systems, using activated chemiluminescence: chemical, with Fenton's reagent (HO-FeSO)-for the generation of hydroxyl radicals (OH); chemical, with oxidant hydrogen peroxide (HO); chemical (NAD.H-PhMS), for the generation of superoxide radicals (O). FeO nanoparticles exhibit highly pronounced antioxidant properties; TiO nanoparticles exhibit mild to moderate prooxidant properties at neutral and alkaline conditions. Those properties are tested by the chemiluminescent method for the first time. Thalicarpine and its combination with TiO nanoparticles exhibit pronounced antioxidant activities at pH 8.5 which are lost and transformed into well-presented prooxidant effects at pH 7.4. That is a result-supported proof on the observed typical properties of thalicarpine and TiO, namely antibacterial, organic-preserving and anti-pathogenic activities. The antimicrobial effect is tested on Gram-positive and Gram-negative bacteria: two strains of Escherichia coli, Bacillus cereus 1095 and Staphylococcus aureus. All bacteria are destroyed after the application of TiO, but not FeO nanoparticles, showing their antibacterial effect. Thalicarpine, in combination with TiO, showed even synergetic antibacterial effect.
Topics: Anti-Infective Agents; Aporphines; Bacteria; Hydrogen Peroxide; Iron; Nanoparticles; Oxidants; Oxidation-Reduction; Reactive Oxygen Species; Titanium
PubMed: 32448965
DOI: 10.1007/s00203-020-01902-2