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Aspects Relating of the Oxidative Stress to Living Organisms | OMICS International
ISSN: 2332-2543
Journal of Biodiversity & Endangered Species
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Aspects Relating of the Oxidative Stress to Living Organisms

Monica Butnariu1* and Ionel Samfira2

1Discipline of Chemistry and Vegetal Biochemistry, Banat’s University of Agricultural Sciences and Veterinary Medicine from Timisoara, Romania

2Discipline of Grassland and Fodder plants culture, Banat’s University of Agricultural Sciences and Veterinary Medicine from Timisoara, Romania

*Corresponding Author:
Monica Butnariu
Discipline of Chemistry and Vegetal Biochemistry
Banat’s University of Agricultural Sciences and Veterinary Medicine from Timisoara
300645, Calea Aradului 119, Timis, Romania
Tel: +40-0-256-277-464
E-mail: [email protected], [email protected]

Received date July 20, 2013; Accepted date July 22, 2013; Published date July 22, 2013

Citation: Butnariu M, Samfira I (2013) Aspects Relating of the Oxidative Stress to Living Organisms. J Biodivers Endanger Species 1:e106. doi:10.4172/2332-2543.1000e106

Copyright: © 2013 Butnariu M. et al, This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

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Free radicals (pro-oxidants) are compounds belonging to the radical groups; they are active biochemically and biologically, and they destroy cell membranes, nuclei, and cytoplasm, producing and maintaining an intense oxidative stress. This is a consequence of the presence of one or several free electrons on the last layer of an atom in the molecule. Free radicals are oxygenated electron-deficit anions that do not make up salts, acids, or bases, but keep this reactive (free) form [1].

Oxygen electronic structure explains why the element, though a free diradical (two unpaired electrons) have low reactivity. Oxygen is essential for aerobic bodies’ life, but, in concentrations that are too high, it can turn toxic. Molecular oxygen in fundamental state is inert, and its partial reduction results in active oxygen species-the most dangerous free radicals [2]. This group of compounds is called Reactive Oxygen Species (ROS). ROS is a term including not only oxygen radicals (O and H), but also oxygen non-radicalic derivatives, including hydrogen peroxide (H2O2), hypochlorous acid (HOCl), and ozone (O3) [3]. Even if ROS are not true free radicals, these species are molecule reactive [4].

Under physiological conditions, ROS are produced in small amounts in the cells [5].

The interaction between these species and lipid membranes, nucleic acids, proteins and enzymes or other small molecules, leads inevitably to cell lesions (Figure 1).


Figure 1: Effects of free radicals.

These cell lesions are one of the factors leading to ageing and degenerative diseases at cell level, there are several types of reactive species.

The variety of free radicals in nature resulted from different processes (ultraviolet radiations, gamma radiations, action of specific particles, etc.) makes their classification difficult [6,7].

From the point of view of the nature of the element containing free electrons, free radicals can be: superoxide, peroxide, hydroxide, nitric oxide, nitrite, nitrate, alkoxyl (Table 1).

Species/Common Name Systematic Name/Alternative and Comments
CO/carbon monoxide carbon monoxide/Oxidomethanediyl (CH3°)
CO2/carbon dioxide carbon dioxide/dioxidomethane
CO2–°/carbon dioxide radical anion dioxidocarbonate (°1–)/oxidooxomethyl radical
CO3–°/carbonate radical trioxidocarbonate (°1–)
H°/hydrogen atom monohydrogen (°)
H2O/water dihydrogen monoxide/oxidane
H2O2/hydrogen peroxide dihybridodioxide/dioxidane
H3C° methyl radical
HNO2 nitrous acid
HNO3 nitric acid
HO°/hydroxyl radical hydridooxygen/oxidanyl
HO2–/ hydridodioxygen (1–) dioxidanide, hydrogendioxide (1–)/hydrogenperoxide (1–)
HO2°/hydroperoxyl, but is obsolete Hydridodioxygen (°) dioxidonyl/hydrodioxyl, perhydroxyl
HO3°/hydrogen trioxide radical hydridotrioxygen (°)/trioxidanyl
HOCO° hydroxidooxidocarbon (°)
HOCO°2 hydroxidodioxidocarbon (°)
HOCl/hypochlorous acid hydrogenoxidochlorate
HOBr/hypobromous acid hydrogenoxidobromate
HOI/hypoiodous acid hydrogenoxidoiodate
HOSCN/hypothiocyanous acid hydrogenoxidothiocyanate
HON2° hydroxidonitrogen(2°) (triplet)/hydrogen oxidonitrate(2°)
HOOCO/ (hydridodioxido) oxidocarbon(°)
HOONO/peroxynitrous acid hydrogenoxidoperoxidonitrate/nitrosodioxidane
(NO)2°– bis (oxidonitrate) (n n ) (°1–)
N2O/nitrous oxide dinitrogen monoxide
N2O–° oxidodinitrate (°1–)
N2O3 dinitrogen trioxide
N3°/azidyl radical trinitrogen (2n – n)(°)
NO°/nitric oxide, but is obsolete oxidonitrogen (°)/oxoazanyl, nitrogen monoxide
NO–(2°)/nitroxyl oxidonitrate (2°1–) (triplet)
NO2–/nitrite dioxidonitrate (1–)
NO2°/nitrogen dioxide dioxidonitrogen
NO22–° dioxidonitrate(°2–)
NO3–/nitrate trioxidonitrate (–)
NO3°/nitrogen trioxide trioxidonitrogen (°)/nitrosoxidanyl
NO32–° trioxidonitrate (°2–)
O°–/radical anion of HO° oxide (°1–)/oxidanidyl
O2°–/superoxide dioxide (°1–)/dioxidanidyl
O2+°/ dioxygen (°1+)
O22°/oxygen, usually O written O2 dioxygen (triplet)/dioxidanediyl
O3/ozone trioxygen
O3°–/ozonide trioxide (°1–)/trioxidanidyl
OCl–/hypochlorite oxidochlorate (1–)
OBr–/hypobromite oxidobromate (1–)
OI–/hypoiodite oxidoiodate (1–)
OSCN–/hypothiocyanate oxidothiocyanate (1–)
OCOO°– (dioxido) oxidocarbonate (°1–)
ONOO–/peroxynitrite oxidoperoxidonitrate (1–)/nitrosodioxidanide
ONOOH/peroxynitrous acid hydrogen–oxidoperoxinitrate/nitrosodioxidane
ONOO° (dioxido)oxidonitrogen (°)/nitrosodioxidanyl

Table 1: Formulae and IUPAC Recommended Names of Simple Compounds Containing C, H, and O in Free Radical Biology

Cell production of ROS roots in enzymatic and non–enzymatic sources.

Electron transfer from proteins or enzymatic systems can lead to ROS as a result of electron transfer reactions. This “unintentional” generation of ROS in mitochondria represents 1-2% of the total O2 consumed in reducing conditions. Body oxygen content represents 65% and inhaled air oxygen content is 21%. Cells generate aerobic energy, reducing O2 to water.

Oxygen can be used in catabolic and anabolic processes, allowing larger amounts of energy than possible in its absence [8].

Oxygen has a particular electronic structure in its fundamental state, with two non-participating electrons on the last layer, each of which is localised on an orbital n* (Figure 2).


Figure 2: Reactive oxygen species

These two electrons have the same quantum number of spin; thus, if O2 tries to oxidate a compound by accepting two electrons, they need to have a parallel spin number to occupy the free spaces in the orbitals n* (in an orbital, two electrons have anti-parallel spins +1/2 and -1/2) [9].

This particularity asks for a restriction of oxidations, determining higher or lower reactivity, depending on the nature of the electron donor (Table 2).

No. Species/Abbreviation Name
1 Asc; AscH–; Asc°– ascorbate, general; ascorbate monoanion; ascorbate radical
2 CAT catalase
3 HRP peroxidase
4 GPx glutathione peroxidase
5 GR glutathione disulfide reductase; often referred to as glutathione reductase
6 Grx glutaredoxin
7 GSH glutathione, not reduced glutathione (a misnomer)
8 GST glutathione S transferase
9 LDL low density lipoprotein
10 OH– hydroxide anion, not to be confused with HO°
11 PUFA polyunsaturated fatty acid
12 RO° alkoxyl radical; not alkoxy
13 ROO° alkyl dioxygen (°), alkyldioxyl, alkylperoxyl radical; not peroxy
14 SOD superoxide dismutase

Table 2: Common Abbreviations.

All oxidations in nature are based on these two pathways, even if the forms may seem varied.

Peroxides and superoxides are anions that have oxidative action (peroxides, alkoxyls, nitrosamines, acrolein) derive from H2O2 and from other sources/processes, like the anions resulted from the degradation (rancidisation, proteolytic degradation, etc.) of lipid-rich foods (lipid peroxides, lipid alkoxyls) or from food processing (frying, refreezing, etc.).

Hypochlorous acid behaves like free radicals (but they do not belong to this class).

Other sources of free radicals are nitrosamines and unsaturated aldehydes (acrolein), very active and destructive because of their action on cell membranes [10].

Evolutively, nature has selected and included in the composition of the organisms, reactions generating free radicals with multiple roles: functional, intracellular communication, or destructive, cytolitic. If, at molecular level, the main target of the free radicals is the free or protein groups SH, at cellular level, the major goal is cell membranes.


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