FRAntioxidhandouts - FREE RADICALS Oxidative stress and...

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FREE RADICALS Oxidative stress and antioxidants in human body
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The nature of free radicals A free radical is a chemical species that contains one or more unpaired electrons Free radicals are extremely reactive, so they have a very short half-life and low steady-state concentration
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Two major forms of free radicals that are formed from oxygen and nitrogen: reactive oxygen species (ROS), and reactive nitrogen species (RNS ). Superoxide (O 2 -• ) and hydroxyl (OH -• ) are examples of reactive oxygen radicals. However, the term reactive oxygen species can also refer to oxygen-derived non-radicals such as hydrogen peroxide (H 2 O 2 ), ozone (O 3 ), hypochlorus acid (HOCl) and singlet oxygen. Nitric oxide (NO -• ) and nitrogen dioxide (NO 2 -• ) are nitrogen radicals, but the term ROS also encompasses certain non-radicals such as nitrous acid (HNO 2 ) and peroxynitrate (ONOO -• ).
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ROS and RNS are formed regularly as a result of normal organ functions, or as a result of excess oxidative stress. Reactive oygen species (ROS) and reactive nitrogen species (RNS)
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Reactive oygen species (ROS) and reactive nitrogen species (RNS) The reactive species superoxide (O 2 •- ), hydrogen peroxide ( H 2 O 2 ), hydroxyl radical (HO•), nitrogen oxide (NO•), peroxynitrite (ONOO-) and hypochlorous acid (HOCl ), are all products of normal metabolic pathways of the human organs, but under certain conditions, when in excess they can exert an harmful compounds.
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Reactive oxygen species
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The main source of HO• are the metal- catalyzed reactions Fenton and Haber-Weiss . These reactions involving transition metals, occur in vivo
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Fenton reaction Fe (II) + H 2 O 2 → Fe (III) + OH - + HO
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Haber – Weiss reaction The concept that the highly reactive hydroxyl radical (HO•) could be generated from an interaction between superoxide (O 2 -• ) and hydrogen peroxide was proposed in Haber-Weiss reaction O 2 -• + H 2 O 2 → • OH + HO - + O 2
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Free Radicals Free radical production in the body is a normal and essential component of cellular metabolism. Some free radicals are formed as biological weapons against viruses, bacteria and cancer cells.
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