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Journal articles on the topic 'Free radicals'

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Author: Grafiati

Published: 4 June 2021

Last updated: 31 July 2024

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1

Yañez Jaramillo, Lina M., Joy H. Tannous, and Arno de Klerk. "Persistent Free Radicals in Petroleum." Processes 11, no. 7 (July 11, 2023): 2067. http://dx.doi.org/10.3390/pr11072067.

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The persistent free radical content in petroleum is of the order 1018 spins/g (1 μmol/g), with higher and lower values found depending on origin and in different distillation fractions. The field of persistent free radicals in petroleum was reviewed with the aim of addressing and explaining apparent inconsistencies between free radical persistence and reactivity. The macroscopic average free radical concentration in petroleum is persistent over geological time, but individual free radical species in petroleum are short-lived and reactive. The persistent free radical concentration in petroleum can be explained in terms of a dynamic reaction equilibrium of free radical dissociation and association that causes a finite number of species at any given time to be present as free radicals. Evidence to support this description are observed changes in free radical concentration related to change in Gibbs free energy when the bulk liquid properties are changed and responsiveness of free radical concentration to dynamic changes in temperature. Cage effects, solvent effects, steric protection, and radical stabilization affect free radical reaction rate but do not explain the persistent free radical concentration in petroleum. The difference between persistent free radicals in straight-run petroleum and converted petroleum is that straight-run petroleum is an equilibrated mixture, but converted petroleum is not at equilibrium and the free radical concentration can change over time. Based on the limited data available, free radicals in straight-run petroleum appear to be part of the compositional continuum proposed by Altgelt and Boduszynski. Persistent free radical species are partitioned during solvent classification of whole oil, with the asphaltenes (n-alkane insoluble) fraction having a higher concentration of persistent free radicals than maltenes (n-alkane soluble) fraction. Attempts to relate persistent free radical concentration to petroleum composition were inconclusive.

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2

Stevanovic, Jelka, Suncica Borozan, Slavoljub Jovic, and Igor Ignjatovic. "Physiology of free radicals." Veterinarski glasnik 65, no. 1-2 (2011): 95–107. http://dx.doi.org/10.2298/vetgl1102095s.

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Free radicals imply that every atom, molecule, ion, group of atoms, or molecules with one or several non-paired electrons in outer orbital. Among these are: nitrogenoxide (NO?), superoxide-anion-radical (O2?-), hydroxyl radical (OH?), peroxyl radical (ROO?), alcoxyl radical (RO?) and hydroperoxyl radical (HO2?). However, reactive oxygen species also include components without non-paired electrons in outer orbital (so-called reactive non-radical agents), such as: singlet oxygen (1O2), peroxynitrite (ONOO-), hydrogen-peroxide (H2O2), hypochloric acid (eg. HOCl) and ozone (O3). High concentrations of free radicals lead to the development of oxidative stress which is a precondition for numerous pathological effects. However, low and moderate concentrations of these matter, which occur quite normally during cell metabolic activity, play multiple significant roles in many reactions. Some of these are: regulation of signal pathways within the cell and between cells, the role of chemoattractors and leukocyte activators, the role in phagocytosis, participation in maintaining, changes in the position and shape of the cell, assisting the cell during adaption and recovery from damage (e.g.caused by physical effort), the role in normal cell growth, programmed cell death (apoptosis) and cell ageing, in the synthesis of essential biological compounds and energy production, as well as the contribution to the regulation of the vascular tone, actually, tissue vascularization.

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3

Li, Guoxiang, Zhongyang Luo, Wenbo Wang, and Jianmeng Cen. "A Study of the Mechanisms of Guaiacol Pyrolysis Based on Free Radicals Detection Technology." Catalysts 10, no. 3 (March 5, 2020): 295. http://dx.doi.org/10.3390/catal10030295.

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In order to understand the reaction mechanism of lignin pyrolysis, the pyrolysis process of guaiacol (o-methoxyphenol) as a lignin model compound was studied by free radical detection technology (electron paramagnetic resonance, EPR) in this paper. It was proven that the pyrolysis reaction of guaiacol is a free radical reaction, and the free radicals which can be detected mainly by EPR are methyl radicals. This paper proposes a process in which four free radicals (radicals 1- C6H4(OH)O*, radicals 5- C6H4(OCH3)O*, methyl radicals, and hydrogen radicals) are continuously rearranged during the pyrolysis of guaiacol.

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4

Senior, Tim. "Free radicals." British Journal of General Practice 69, no. 688 (October 31, 2019): 572. http://dx.doi.org/10.3399/bjgp19x706493.

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5

ROYSTON, D. "Free radicals." Anaesthesia 43, no. 4 (February 22, 2007): 315–20. http://dx.doi.org/10.1111/j.1365-2044.1988.tb08984.x.

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6

Pilcher, Jobeth. "Free Radicals." Neonatal Network 21, no. 7 (January 2002): 33–37. http://dx.doi.org/10.1891/0730-0832.21.7.33.

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Free radicals may be the cause of many neonatal complications, such as chronic lung disease and brain injury. Treatment options for these complications using antioxidants are being evaluated through research. This article begins with a review of the basic science of free radicals. It then discusses neonatal complications potentially caused by free radicals. A brief description of research into potential treatment options is also included.

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7

Mishler, Susanna. "Free Radicals." Iowa Review 36, no. 3 (December 2006): 138. http://dx.doi.org/10.17077/0021-065x.6221.

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8

Van Lente, Frederick. "Free Radicals." Analytical Chemistry 65, no. 12 (June 15, 1993): 374–77. http://dx.doi.org/10.1021/ac00060a601.

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9

Homandberg, Gene A. "FREE RADICALS." Shock 7, no. 4 (April 1997): 312. http://dx.doi.org/10.1097/00024382-199704000-00015.

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10

Angel, Michael F., Sai S. Ramasastry, William M. Swartz, R. E. Basford, and J. William Futrell. "Free Radicals." Plastic and Reconstructive Surgery 79, no. 6 (June 1987): 990. http://dx.doi.org/10.1097/00006534-198706000-00025.

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11

Buttriss, Judy. "FREE RADICALS." Nutrition & Food Science 89, no. 1 (January 1989): 12–13. http://dx.doi.org/10.1108/eb059214.

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12

Dodd, "N J. F. "Free radicals and food irradiation." Biochemical Society Symposia 61 (November 1, 1995): 247–58. http://dx.doi.org/10.1042/bss0610247.

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Ionizing radiation can be used to control insect and microbial infestation of foodstuffs, inhibit sprouting, delay ripening and reduce the dangers from food-poisoning bacteria. Irradiation produces free radicals, most of which decay rapidly, although some are more persistent. These latter radicals can be detected and characterized by electron spin resonance (ESR). In bone and other calcified tissues, the radiation-induced radicals are distinguishable from naturally occurring radicals, and their stability makes them ideal for radiation dosimetry. The radicals induced in plant material, such as seeds and dried spices, are generally indistinguishable from the endogenous radicals and decay over a period of days or weeks. However, in many of these materials, a radiation-specific radical can be detected at low concentration, thereby permitting identification of irradiated samples, although precluding accurate dosimetry. ESR, although not universally applicable, currently provides the most specific method for the detection of irradiated food.

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13

Mikayil Aliyev, Mirza, Ulduz Yunis Safarova, and Shafiqa Jahangir Jafarova. "CHARACTERISTICS AND THERAPEUTIC EFFECTS OF THE NOVEL FREE RADICAL SCAVENGER – EDARAVONE." NATURE AND SCIENCE 04, no. 05 (December 28, 2020): 17–20. http://dx.doi.org/10.36719/2707-1146/05/17-20.

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Edaravone is the first free radical scavenger which approved clinically and has an ability to decrease the level of free radicals in cells. Edaravone is a strong antioxidant, which can protect different cells (e.g. endothelial cells) against damage by ROS by inhibiting the lipoxygenase metabolism of arachidonic acid, by trapping hydroxyl radicals, by increasing prostacyclin production, by inhibiting alloxan-induced lipid peroxidation, etc. Because of that, Edaravone is used in treatment of diseases which are associated with oxidative stress. Key words: edaravone, free radical, antioxidant, neuroprotective agent, oxidative stress

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14

Kim, Eun-Kyung, and Mi Ryeong Song. "Factors Influencing the Level of Oxygen Free Radicals in Female Nursing Students." Global Journal of Health Science 11, no. 7 (May 15, 2019): 1. http://dx.doi.org/10.5539/gjhs.v11n7p1.

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This study was conducted to investigate the levels of oxygen free radicals and related health factors in 201 female nursing students. The questionnaire was completed by the participants and their oxygen free radical levels were measured by urine test. In this study, an oxygen free radical analyzer was used to measure oxygen free radical levels. The oxygen free radical analyzer analyzes the amount of oxygen free radicals in the body by measuring urinary malondialdehyde (MDA). To determine factors associated with oxygen free radical levels, multiple regression tests were conducted. Of the participants, 89.6% exhibited normal levels of oxygen free radicals and 10.4% had elevated levels. In this study, the factors that affected oxygen free radical levels were eating habit (β = .20, p =. 003), fatigue (β = .20, p = .004), and detox necessity (β = .18, p = .006). In order to lower oxygen free radical levels of female nursing students, the areas of eating habit, fatigue, and detox must receive increased focus.

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15

Vergely, Catherine, and Rochette Luc. "Forgotten Radicals in Biology." International Journal of Biomedical Science 4, no. 4 (December 15, 2008): 255–59. http://dx.doi.org/10.59566/ijbs.2008.4255.

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Redox reactions play key roles in intra- and inter-cellular signaling, and in adaptative processes of tissues towards stress. Among the major free radicals with essential functions in cells are reactive oxygen species (ROS) including superoxide anion (O2-), hydroxyl radical (OH) and reactive nitrogen species (RNS) such as nitric oxide (NO). In this article, we review the forgotten and new radicals with potential relevance to cardiovascular pathophysiology. Approximately 0.3% of O2- present in cytosol exists in its protonated form: hydroperoxyl radical (HO2). Water (H2O) can be split into two free radicals: OH and hydrogen radical (H). Several free radicals, including thiyl radicals (RS) and nitrogen dioxide (NO2) are known to isomerize double bonds. In the omega-6 series of poly-unsaturated fatty acids (PUFAs), cis-trans isomerization of γ-linolenate and arachidonate catalyzed by RS has been investigated. Evidence is emerging that hydrogen disulphide (H2S) is a signaling molecule in vivo which can be a source of free radicals. The Cu-Zn superoxide dismutase (SOD) enzyme can oxidize the ionized form of H2S to hydro-sulphide radical: HS. Recent studies suggest that H2S plays an important function in cardiovascular functions. Carbonate radical, which can be formed when OH reacts with carbonate or bicarbonate ions, is also involved in the activity of Cu-Zn-SOD. Recently, it has been reported that carbonate anion were potentially relevant oxidants of nucleic acids in physiological environments. In conclusion, there is solid evidence supporting the formation of many free radicals by cells leading which may play an important role in their homeostasis.

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16

ZHDANOV, R. I. "ChemInform Abstract: Nitroxyl Radicals and Non-Radical Reactions of Free Radicals." ChemInform 24, no. 31 (August 20, 2010): no. http://dx.doi.org/10.1002/chin.199331310.

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17

Jonsson, M., J. Lind, T. Reitberger, T. E. Eriksen, and G. Merenyi. "Free radical combination reactions involving phenoxyl radicals." Journal of Physical Chemistry 97, no. 31 (August 1993): 8229–33. http://dx.doi.org/10.1021/j100133a018.

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18

Reimer, Keith A., Masaru Tanaka, Charles E. Murry, Vincent J. Richard, and Robert B. Jennings. "Evaluation of Free Radical Injury in Myocardium." Toxicologic Pathology 18, no. 4a (January 1990): 470–80. http://dx.doi.org/10.1177/0192623390004part_105.

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Abundant evidence now is available that free radicals are produced in excess when myocardium is reperfused following an episode of ischemia and that free radicals can injure myocytes and endothelial cells. Free radicals may contribute to either reversible or irreversible manifestations of cell injury from ischemia and reperfusion. Several investigators have observed that postischemic contractile dysfunction (myocardial stunning) can be attenuated by a variety of anti-free radical therapies, and there seems to be general agreement that free radical injury contributes to stunning. Whether free radicals are an important cause of lethal myocyte injury (“lethal reperfusion injury”) remains controversial. Using similar interventions and animal models, both positive and negative results have been reported from a growing number of studies done to test the effect of anti-free radical therapies on infarct size. Proposed explanations include differences in: 1) dose of drug and onset or duration of treatment, 2) duration of occlusion or reperfusion, 3) methods of measuring infarct size or area at risk, and 4) failure of some studies to control for baseline variation in the major determinants of infarct size, e.g., collateral blood flow. At present, none of these explanations seems sufficient to resolve the question.

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19

Matsugo, Seiichi, Masashi Mizuno, and Tetsuya Konishi. "Free Radical Generating and Scavenging Compounds as a New Type of Drug." Current Medicinal Chemistry 2, no. 4 (December 1995): 763–90. http://dx.doi.org/10.2174/092986730204220224092844.

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Abstract: Recently, the free radical investigations cover a broad field of research related to chemistry, biology, medicine and biochemistry. One of the reasons for this is that the free radicals play crutial roles in many pathogenic disorders, typically carcinogenesis. So, in this sense it is very important to elucidate the precise mechanism of action of free radicals in vivo from the aspect of tumor necrosis. Indeed, many drugs have been extensively studied in relation to free radicals in recent years. These studies can be divided into two categories one of which emphasizes the advantageous side of free radicals, while the other emphasizes the toxic aspects of free radicals. In tis review article, we will discuss four major studies related free radical studies based on the chemical standpoint of view. Frist we will introduce the recent advances of radical generating drugs such as bleomycin and some ene-diyne natural products in the medicinal field. Second, we will introduce the possible use of free radical generating compounds as a condidate of the new-type of drug. Third, we will show the protective effects and importance of some recent advances in antioxidants research, which show the potentiality of natural antioxidants as the protective or therapeutic medicine for free radical deseases. Finally, we will introduce some recent progress in the gene-regulation studies by the antioxidants and show our ideas for the future application for this concept in the medicinal fields.

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20

Keah, HH, ID Rae, and DG Hawthorne. "E.S.R. Spectra of Free Radicals Relevant to Methacrylate Polymerization." Australian Journal of Chemistry 45, no. 4 (1992): 659. http://dx.doi.org/10.1071/ch9920659.

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Carbon-based free radicals were generated by thermal cleavage of the tetraester Me2C(COOME)-CH2-CMe( COOMe )- CMe ( COOMe )-CH2-C( COOMe )Me2 which is a model for head-to-head units in a poly(methyl methacrylate ) chain. The resulting electron spin resonance spectrum had higher resolution than the 'nine-line' spectrum previously reported; this enabled identification of the component radicals. In the present case, the spectrum was well matched by a summation of spectra of the Me2C(COOME)-CH2-CMe( COOMe ) radical and the 1-methoxycarbonyl-1-methylethyl radical Me2-C-COOMe derived from it by loss of methyl methacrylate. Both of these radicals were generated in separate experiments. Radicals were also generated from starting materials containing a CD3 group in place of the single CH3.

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21

Jarco, Sylwia, Barbara Pilawa, and Paweł Ramos. "Free Radical Scavenging Activity of Infusions of Different Medicinal Plants for Use in Obstetrics." Plants 10, no. 10 (September 26, 2021): 2016. http://dx.doi.org/10.3390/plants10102016.

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An X-band (9.3 GHz) electron paramagnetic resonance (EPR) spectroscopy was used to examine the free radical scavenging activity of the following infusions, which were nonirradiated and exposed to UVA: root of Asparagus racemosus and herbs of Mitchella repens, Cnicus benedictus L., Galega officinalis L., and Eupatorium cannabinum L. The plant materials for obstetrics applications were chosen for analysis. The aims of these studies were to compare the free radical scavenging ability of the tested infusions and to determine the influence of UVA irradiation of the plant materials on interactions of these infusions with free radicals. Both the magnitude and kinetics of the interactions of the infusions with the model DPPH free radicals were examined. The ability to quench the free radicals for the examined plant infusions increases in the following order: Asparagus racemosus (root) < Mitchella repens (herb) < Cnicus benedictus L. (herb) < Galega officinalis L. (herb) < Eupatorium cannabinum L. (herb). The analyzed infusions differ in the kinetics of the interactions with free radicals. The fastest interactions with free radicals characterize the infusions of Galega officinalis L. herb and Eupatorium cannabinum L. herb. The infusion of Mitchella repens herb interacts with free radicals in the slowest way. UVA radiation reduces the antioxidant interactions of all tested infusions, especially the infusion of Eupatorium cannabinum L. herb, which should be protected against UVA radiation during storage. The weakest decrease of free radical scavenging activity was observed for the infusion of the root of Asparagus racemosus exposed to UVA radiation. UVA radiation affected the speed of the free radical interactions of the infusions, depending on the type of plant materials. EPR spectroscopy is useful to examine the free radical scavenging activity of plant infusions, which is helpful to find effective antioxidants for applications in obstetrics and their optimal storage conditions.

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22

Murrell, G. A. C., M. J. O. Francis, and L. Bromley. "Modulation of fibroblast proliferation by oxygen free radicals." Biochemical Journal 265, no. 3 (February 1, 1990): 659–65. http://dx.doi.org/10.1042/bj2650659.

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The major unexplained phenomenon in fibrotic conditions is an increase in replicating fibroblasts. In this report we present evidence that oxygen free radicals can both stimulate and inhibit proliferation of cultured human fibroblasts, and that fibroblasts themselves release superoxide (O2.-) free radicals. Fibroblasts released O2.- in concentrations which stimulated proliferation, a finding confirmed by a dose-dependent inhibition of proliferation by free radical scavengers. Oxygen free radicals released by a host of agents may thus provide a very fast, specific and sensitive trigger for fibroblast proliferation. Prolonged stimulation may result in fibrosis, and agents which inhibit free radical release may have a role in the prevention of fibrosis.

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23

Fuentes-Lemus, E., E. Dorta, E. Escobar, A. Aspée, E. Pino, M. L. Abasq, H. Speisky, et al. "Oxidation of free, peptide and protein tryptophan residues mediated by AAPH-derived free radicals: role of alkoxyl and peroxyl radicals." RSC Advances 6, no. 63 (2016): 57948–55. http://dx.doi.org/10.1039/c6ra12859a.

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When AAPH is employed as a free radical source, at low concentrations of free, peptide and protein Trp residues, the oxidation is mostly induced by alkoxyl radicals. However, at high concentrations, both peroxyl and alkoxyl radicals are involved.

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24

Mitrohina, Natal'ya. "Oxidative stress in animals: role in oncogenesis from pathomorphologist view." Russian veterinary journal 2020, no. 5 (November 25, 2020): 27–30. http://dx.doi.org/10.32416/2500-4379-2020-5-27-30.

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Oxidative stress is a pathological accumulation of free radicals that contribute to the launch of intracellular damaging action mechanisms. Free radical is an atom possessing free or missing electron, and seeking to restore the lost electron, taking it from other molecules ― as a result a new free radical is formed. The mechanism is chain reaction-based. Hypoxia acts as an additional stimulus to the appearance of oxygen free radicals. Cell hypoxia develops following any type of cell damage: mechanical, bacteriological, chemical, etc. Cell hypoxia inevitably leads to the development of an inflammatory reaction, which is followed by the formation of oxygen free radicals and, as a result, by oxidative stress development.

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25

Karl, Oettl, Joachim Greilberger, and Gilbert Reibnegger. "Modulation of Free Radical Formation by Pterin Derivatives." Pteridines 15, no. 3 (August 2004): 97–101. http://dx.doi.org/10.1515/pteridines.2004.15.3.97.

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Abstract All classes of pterins, fully reduced tetrahydropterins, aromatic pterins and dihydropterins have been investigated upon their effects on radical mediated reactions. Meanwhile all these classes were shown to act as both, proand antioxidants by a number of different methods including chemical, biochemical and biological systems. From reduced pterins radicals including oxygen-, nitrogen- and pterin-radicals arc formed enzymatically and non-enzymatically, reduced pterins react with free radicals and serve as reductive agents. All classes of pterins may interfere with enzymes involved in radical formation. Upon the diversity of possibilities the net effect of a particular compound is a question of the experimental settings and the physiological relevant role often remains obscure.

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26

Hall, Dale. "Free Radicals: Iz." Electrochemical Society Interface 9, no. 4 (December 1, 2000): 17. http://dx.doi.org/10.1149/2.f02004if.

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27

Hall, Dale. "Free Radicals: Battlebots." Electrochemical Society Interface 11, no. 3 (September 1, 2002): 9–18. http://dx.doi.org/10.1149/2.f01023if.

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28

Hall, Dale. "Free Radicals: Wired." Electrochemical Society Interface 7, no. 4 (December 1, 1998): 15–43. http://dx.doi.org/10.1149/2.f02984if.

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29

Hall, Dale. "Free Radicals: Cybersurfing." Electrochemical Society Interface 4, no. 1 (March 1, 1995): 15. http://dx.doi.org/10.1149/2.f01951if.

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30

Baba, Lisa, and Jacqueline M. McGrath. "Oxygen Free Radicals." Advances in Neonatal Care 8, no. 5 (October 2008): 256–64. http://dx.doi.org/10.1097/01.anc.0000338015.25911.8a.

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31

POWELL, RICHARD J., GEORGE W. MACHIEDO, BENJAMIN F. RUSH, and GEORGE DIKDAN. "Oxygen free radicals." Critical Care Medicine 19, no. 5 (May 1991): 732–35. http://dx.doi.org/10.1097/00003246-199105000-00022.

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32

Granger, D. Neil, and Dale A. Parks. "Incarcerate free radicals." Hepatology 6, no. 3 (May 1986): 536–37. http://dx.doi.org/10.1002/hep.1840060339.

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33

Voelker, R. "Measuring Free Radicals." JAMA: The Journal of the American Medical Association 279, no. 16 (April 22, 1998): 1249—a—1249. http://dx.doi.org/10.1001/jama.279.16.1249-a.

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34

Voelker, Rebecca. "Measuring Free Radicals." JAMA 279, no. 16 (April 22, 1998): 1249. http://dx.doi.org/10.1001/jama.279.16.1249-jqu80001-2-1.

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35

North, J. A., A. A. Spector, and G. R. Buettner. "Cell fatty acid composition affects free radical formation during lipid peroxidation." American Journal of Physiology-Cell Physiology 267, no. 1 (July 1, 1994): C177—C188. http://dx.doi.org/10.1152/ajpcell.1994.267.1.c177.

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Lipid-derived free radicals generated from intact human U937 monocytes exposed to iron-induced oxidative stress were detected by electron paramagnetic resonance (EPR) with the spin trap alpha-(4-pyridyl-1-oxide)-N-tert-butylnitrone (POBN). Lipid radical formation was enhanced when the cells were enriched with n-3 or n-6 polyunsaturated fatty acids. Computer simulation indicated that at least two POBN spin adducts were formed, having spectral characteristics consistent with carbon-centered radicals (aN = 15.9 G and aH = 2.6 G; aN = 15.1 G and aH = 2.8 G). These alkyl radicals are probably formed by beta-scission of alkoxyl radicals. POBN spin adduct formation correlated with ethane generation. Addition of ascorbate to the assay medium greatly increased the radical signal intensity. Although radical generation was cell dependent and POBN spin adducts were observed in cell homogenates, the adducts formed by the intact cells were detected only in the extracellular medium. These findings indicate that the extent of lipid radical formation in response to oxidative stress can be influenced by changes in the polyunsaturated fatty acid composition of the cell lipids and suggest the possibility that carbon-centered lipi radicals may interact with extracellular structures.

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36

Davies, M. J., S. Fu, and R. T. Dean. "Protein hydroperoxides can give rise to reactive free radicals." Biochemical Journal 305, no. 2 (January 15, 1995): 643–49. http://dx.doi.org/10.1042/bj3050643.

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Proteins damaged by free-radical-generating systems in the presence of oxygen yield relatively long-lived protein hydroperoxides. These hydroperoxides have been shown by e.p.r. spectroscopy to be readily degraded to reactive free radicals on reaction with iron(II) complexes. Comparison of the observed spectra with those obtained with free amino acid hydroperoxides had allowed identification of some of the protein-derived radical species (including a number of carbon-centred radicals, alkoxyl radicals and a species believed to be the CO2 radical anion) and the elucidation of novel fragmentation and rearrangement processes involving amino acid side chains. In particular, degradation of hydroperoxide functions on the side chain of glutamic acid is shown to result in decarboxylation at the side-chain carboxy group via the formation of the CO2 radical anion; the generation of an identical radical from hydroperoxide groups on proteins suggests that a similar process occurs with these molecules. In a number of cases these fragmentation and rearrangement reactions give rise to further reactive free radicals (R., O2-./HO2., CO2-.) which may act as chain-carrying species in protein oxidations. These studies suggest that protein hydroperoxides are capable of initiating further radical chain reactions both intra- and inter-molecularly, and provide information on some of the fundamental mechanisms of protein alteration and side-chain fragmentation.

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37

Valcheva-Traykova, Maria L., Trayko T. Traykov, and Georgeta S. Bocheva. "Interaction Of Propylthiouracil With Model Systems Generating A Superoxide Radical." Journal of Biomedical and Clinical Research 7, no. 2 (December 1, 2014): 93–98. http://dx.doi.org/10.1515/jbcr-2015-0132.

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SummaryPropylthiouracil is used against Grave's Disease and for developing animal models of hypothyroidism. Apart from depressed metabolism, free radical-induced tissue damage has been registered as an effect from this drug. Superoxide is essential for generation of free radicals in tissues. The mutual effects of Propylthiouracil and superoxide radical have not been well investigated.Thein vitroeffects of Propylthiouracil on the free radicals in three model systems generating superoxide were measured using luminol-dependent chemiluminescence and spectrophotometry. The drug did not affect the formation of free radicals in the presence of potassium superoxide and in pyrogallol-oxygen solutions, while in the presence of the xanthine/xanthine oxidase system a distinct prooxidant effect was registered. The investigation of the system propylthiouracil/xanthine oxidase showed mild free radicals formation along with decreasing intensities of the drug's UV-specter.Ourin vitroinvestigation indicated that, along with the transformation of xanthine to uric acid over xanthine oxidase, some free radicals may be produced due to the interaction of propylthiouracil with the enzyme. It was proposed that this might contribute to thein vivofree radicals-induced tissue damage observed in the presence of propylthiouracil.

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38

Inoue, Gen, Yuhei Ohtaki, Kazue Satoh, Yuki Odanaka, Akihito Katoh, Keisuke Suzuki, Yoshitake Tomita, et al. "Sedation Therapy in Intensive Care Units: Harnessing the Power of Antioxidants to Combat Oxidative Stress." Biomedicines 11, no. 8 (July 28, 2023): 2129. http://dx.doi.org/10.3390/biomedicines11082129.

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In critically ill patients requiring intensive care, increased oxidative stress plays an important role in pathogenesis. Sedatives are widely used for sedation in many of these patients. Some sedatives are known antioxidants. However, no studies have evaluated the direct scavenging activity of various sedative agents on different free radicals. This study aimed to determine whether common sedatives (propofol, thiopental, and dexmedetomidine (DEX)) have direct free radical scavenging activity against various free radicals using in vitro electron spin resonance. Superoxide, hydroxyl radical, singlet oxygen, and nitric oxide (NO) direct scavenging activities were measured. All sedatives scavenged different types of free radicals. DEX, a new sedative, also scavenged hydroxyl radicals. Thiopental scavenged all types of free radicals, including NO, whereas propofol did not scavenge superoxide radicals. In this retrospective analysis, we observed changes in oxidative antioxidant markers following the administration of thiopental in patients with severe head trauma. We identified the direct radical-scavenging activity of various sedatives used in clinical settings. Furthermore, we reported a representative case of traumatic brain injury wherein thiopental administration dramatically affected oxidative-stress-related biomarkers. This study suggests that, in the future, sedatives containing thiopental may be redeveloped as an antioxidant therapy through further clinical research.

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Zhao, Zizhen, Chen Fu, Yuping Zhang, and Ailing Fu. "Dimeric Histidine as a Novel Free Radical Scavenger Alleviates Non-Alcoholic Liver Injury." Antioxidants 10, no. 10 (September 27, 2021): 1529. http://dx.doi.org/10.3390/antiox10101529.

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Non-alcoholic liver injury (NLI) is a common disease worldwide. Since free radical damage in the liver is a crucial initiator leading to diseases, scavenging excess free radicals has become an essential therapeutic strategy. To enhance the antioxidant capacity of histidine, we synthesized a protonated dimeric histidine, H-bihistidine, and investigated its anti-free radical potential in several free-radical-induced NLI. Results showed that H-bihistidine could strongly scavenge free radicals caused by H2O2, fatty acid, and CCl4, respectively, and recover cell viability in cultured hepatocytes. In the animal model of nonalcoholic fatty liver injury caused by high-fat diet, H-bihistidine reduced the contents of transaminases and lipids in serum, eliminated the liver’s fat accumulation, and decreased the oxidative damage. Moreover, H-bihistidine could rescue CCl4-induced liver injury and recover energy supply through scavenging free radicals. Moreover, liver fibrosis prepared by high-fat diet and CCl4 administration was significantly alleviated after H-bihistidine treatment. This study suggests a novel nonenzymatic free radical scavenger against NLI and, potentially, other free-radical-induced diseases.

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West, Robert, Kerim Samedov, Amitabha Mitra, Paul W. Percival, Jean-Claude Brodovitch, Graeme Langille, Brett M. McCollum, et al. "Germanium-centered free radicals studied by muon spin spectroscopy." Canadian Journal of Chemistry 92, no. 6 (June 2014): 508–13. http://dx.doi.org/10.1139/cjc-2013-0427.

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Transverse-field muon spin rotation (TF-μSR) spectra have been recorded for free radicals formed by positive muon irradiation of nine different divalent germanium compounds. Muon-electron hyperfine coupling constants (Aμ) were determined from the spectra and compared with values predicted from density functional theory molecular orbital (DFT-MO) calculations on the muoniated radicals formed by muonium addition to the germanium atom. The muon hyperfine constants for germylenes containing N–Ge bonds are generally quite large, from 593 to 942 MHz, indicating strong interaction between the muon and the unpaired electron in these radicals. The radical derived from one of the germylenes exhibited a significantly lower muon hyperfine constant, suggesting that in this case the muoniated germyl radical undergoes a coupling reaction to form a digermanyl radical, which is what is detected by μSR.

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Walton, John, and Ffrancon Williams. "The Games Radicals Play: Special Issue on Free Radicals and Radical Ions." Molecules 20, no. 2 (February 9, 2015): 2831–34. http://dx.doi.org/10.3390/molecules20022831.

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Nakazawa, H., K. Ichimori, Y. Shinozaki, H. Okino, and S. Hori. "Is superoxide demonstration by electron-spin resonance spectroscopy really superoxide?" American Journal of Physiology-Heart and Circulatory Physiology 255, no. 1 (July 1, 1988): H213—H215. http://dx.doi.org/10.1152/ajpheart.1988.255.1.h213.

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A recent study has indicated that the generation of an oxygen radical in freeze-clamped myocardium on reperfusion can be directly demonstrated using electron-spin resonance spectroscopy (ESR). However, the results need to be analyzed with caution, since artifactual radicals are misleading problems common to this method. To test whether that reported superoxide is truly the biologically existing radical or an artifactual radical, we performed experiments using isolated, perfused rat and rabbit hearts and open-chest canine hearts subjected to ischemia/reperfusion. Radicals were freeze trapped at 77 degrees K, and ESR measurements were made. The ESR spectra exhibited four free radicals. Among these, two radicals which had been previously claimed as superoxide and a nitrogen-centered radical were shown as mechanically yielded artifactual radicals. These were produced by pulverization of the frozen sample. In artifact-free samples, superoxide could not be detected. The radicals native to the myocardium were identified as coenzyme Q10-. and another radical the species of which remains unclear.

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Wang, Chen, Rui Chen, Ruyu Zhang, and Naidong Zhang. "Simple spectrophotometric determination of sulfate free radicals." Analytical Methods 10, no. 28 (2018): 3470–74. http://dx.doi.org/10.1039/c8ay01194j.

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A rapid and simple method for sulfate radical determination was described and the generation rates of sulfate radicals generated by photolysis of persulfate under different light sources were studied.

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Awadelkarim, O., O. Claesson, and A. Lund. "Free Radicals in X-Irradiated Ethylene Glycol Crystals." Zeitschrift für Naturforschung A 43, no. 7 (July 1, 1988): 633–37. http://dx.doi.org/10.1515/zna-1988-0704.

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Abstract ESR experiments aiming at clarifying the structure of radicals present in X-irradiated crystals of ethylene glycol and other diols are reported. By comparison with data for the corresponding glasses it is concluded that a major source of free radicals is the decomposition of trapped electrons. The radical structure is identified.

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Nagendrappa, G. "An appreciation of free radical chemistry 6. Experiments involving free radicals." Resonance 10, no. 9 (September 2005): 79–84. http://dx.doi.org/10.1007/bf02896323.

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Salvemini, Daniela, and Regina Botting. "Modulation of platelet function by free radicals and free-radical scavengers." Trends in Pharmacological Sciences 14, no. 2 (February 1993): 36–42. http://dx.doi.org/10.1016/0165-6147(93)90028-i.

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Rahman, Arif, Abd Malik, and Aktsar Roskiana Ahmad. "SKRINING FITOKIMIA DAN UJI AKTIVITAS ANTIOKSIDAN EKSTRAK ETANOLIK BUAH BUNI (Antidesma bunius (L.) SPRENG)." Jurnal Fitofarmaka Indonesia 3, no. 2 (July 5, 2016): 159–63. http://dx.doi.org/10.33096/jffi.v3i2.497.

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Free radicals play a role in the occurrence of various degenerative diseases that require free-radical scavengers or antioxidants. Buni fruit (Antidesma bunius (L.) Spreng) has the bioactive components are Anthocyanins (flavonoids) that serves to the free radicals. This study aimed to measure the antioxidant activity of theethanol extract contained 70% fruit Buni obtained by using the method of nitric oxide. Simplicia buni macerated dried fruit with 70% ethanol. Extracts were obtained in the test antioxidant activity against nitric oxide radicals. The antioxidant activity against free radical absorbance measured by means of UV-Vis spectrophotometry at a wavelength of 546 nm and calcul ated IC50 values. The results shows that the fruit buni has potential as a free radical with IC50 value of 2.28 µg/mL and a comparison of quercetin with IC50 value of 5.88 µg/mL.

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De Schutter, Coralie, Emmanuel Pfund, and Thierry Lequeux. "Radical conjugate addition of ambiphilic fluorinated free radicals." Tetrahedron 69, no. 29 (July 2013): 5920–26. http://dx.doi.org/10.1016/j.tet.2013.05.006.

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Dwimayasanti, Rany. "RUMPUT LAUT: ANTIOKSIDAN ALAMI PENANGKAL RADIKAL BEBAS." OSEANA 43, no. 2 (October 30, 2018): 13–23. http://dx.doi.org/10.14203/oseana.2018.vol.43no.2.17.

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SEAWEED: NATURAL ANTIOXIDANT FREE RADICAL ANTIDOTE. Free radicals are the result of various complex chemical processes in the body, in form of oxidation process, cell metabolism, UV irradiation, environmental pollution such as cigarette smoke, and other pollutants. The effects of free radicals can be prevented by addition of antioxidants endogenously from outside the body. Seaweed is one source of natural antioxidants that is safe for the body. Seaweed contains bioactive compounds that are able to prevent free radicals such as carotenoids, phenols, vitamins and minerals.

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Rumagit, Benedicta Irene, Adeanne Caroline Wullur, and Donald Emilio Kalonio. "ANTI-OXIDANT ACTIVITY OF SESEWANUA (Clerodendrum fragrans [Vent.] Willd) LEAF EXTRACT AND FRACTION WITH 1,1-DiPHENYLl-2-PICRYLHYDRAZYL (DPPH) AND NITRATE-OXIDE FREE RADICAL SCAVENGING METHOD." International Research Journal of Pharmacy 11, no. 11 (November 30, 2020): 68–72. http://dx.doi.org/10.7897/2230-8407.111199.

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Free radicals are molecules containing unpaired electrons so that they are not stable and very reactive to other molecules. ROS/RNS radicals have physiological function, but the overproduction of free radicals can initiate oxidative/nitrosative stress that contributes to a high number of diseases. Body has an ability to neutralize the free radicals by forming the endogenous antioxidant. Environmental changes, living style, certain pathological conditions can cause the shift of prooxidant-antioxidant equilibrium. Thus, endogenous antioxidant intake is needed, particularly that originating from natural materials. One of the plants believed to have antioxidant activity is sesewanua (Clerodendrum fragrans [Vent.] Willd.) leaf. This study was aimed to evaluate the antioxidant activity of ethanol extract, hexane fraction, ethyl acetate fraction, and water fraction of the sesewanua leaf using DPPH and nitrate-oxide free radical scavenging method. The study is a laboratory experiment. The sample was sesewanua (Clerodendrum fragrans) obtained from East Malalayang I village, Malalayang district, Manado city, North Sulawesi. The antioxidant activity testing utilized 1,1-Diphenyl-2-Picrylhydrazyl (DPPH) and nitrate-oxide free radical scavenging method. Data included percent inhibition of free radicals and were analyzed using linear regression to determine 50% inhibition concentration (IC50) of DPPH and nitrate-oxide free radicals. As conclusion, the ethanol extract, hexane fraction, ethyl acetate fraction, and water fraction of the sesewanua leaf had antioxidant activity through DPPH free antiradical activity, but not active as antiradical NO.

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