Free radicals & antioxidant-OPCs

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A Periodic Table of the Elementshttp://en.wikipedia.org/wiki/Valence_(chemistry)

Valence Electronshttp://en.wikipedia.org/wiki/Valence_electrons

Valence Shell In chemistry, free radicals are atoms, molecules or ions with unpaired electrons on a valence shell configuration.

VSEPR theory Valence Shell Electron Pair Repulsion

The pairs of electrons may be bonding or nonbonding (also called lone pairs). Only valence electrons of the central atom influence the molecular shape in a meaningful way.

Octet RuleIn simple terms, Molecules or ions tend to be more stable when the outermost electron shell of their constituent atoms contain eight electrons.

Free radicals These unpaired electrons are usually highly reactive, so radicals are likely to take part in chemical reactions.

Free radicals

The triphenylmethyl radical is a persistent radical and the first ever radical described in organic chemistry.

--- by Moses Gomberg in 1900 at the University of Michigan http://en.wikipedia.org/wiki/Free_radicals

Free radicals

http://en.wikipedia.org/wiki/Triphenylmethyl_radical

Free radicals in chemical reactions In chemistry, chain reactions involving free radicals can usually be divided into three distinct processes: initiation propagation termination

Free radicals in chemical reactions

...initiation

..propagation

...termination

Free radicals in chemical reactions

Long lived radicals can be placed into two categories Stability and Persistence

Free radicals in chemical reactions

Stable Radicals The prime example of a stable radical is molecular dioxygen O2 ( OO ) The oxygen molecule is a stable diradical, best represented by OO

Free radicals in chemical reactions

Spins The ground state of oxygen is an unreactive spin-unpaired (triplet) diradical, but an extremely reactive spin-paired (singlet) state is available.

Free radicals in chemical reactions

http://en.wikipedia.org/wiki/Singlet_oxygentripletsinglet

Free radicals in chemical reactions

Stable Radicals Organic radicals can be long lived if they occur in a conjugated system ( resonance stabilization ), such as the radical derived from -tocopherol (vitamin E). p.28

Free radicals in chemical reactions

http://en.wikipedia.org/wiki/Free_radicals

Free radicals in chemical reactions- caroteneConjugated system

Free radicals in chemical reactions

Persistent Radicals Persistent radical compounds are those whose longevity is due to steric effect around the radical center and makes it physically difficult for the radical to react with another molecule.

Free radicals in chemical reactions

Persistent Radicals http://en.wikipedia.org/wiki/Triphenylmethyl_radicalsteric effect

Free radicals in chemical reactions Persistent Radicals http://en.wikipedia.org/wiki/Triphenylmethyl_radical

Redox reactions Radicals may also be formed by single electron oxidation or reduction of an atom or molecule.

Redox reactions

Redox (reduction-oxidation reaction)

describes all chemical reactions in which atoms have their oxidation number (oxidation state) changed.

Redox reactions Reduction describes the gain of electrons by a molecule, atom or ion.

Reduction is defined as a decrease in oxidation number.

Redox reactions

Oxidation describes the loss of electrons by a molecule, atom or ion.

Oxidation is defined as an increase in oxidation number.

Redox reactions

In practice, the transfer of electrons will always cause a change in oxidation number.

Redox reactions ascorbic acid dehydroascorbic acid (reduced form) (oxidized form)Vitamin Chttp://en.wikipedia.org/wiki/Ascorbic_acid

Redox reactionsResonance effectp.16

Redox reactions in biology

Vitamin C accumulates in mitochondria, where most of the free radicals are produced. Ascorbic acid protects the mitochondrial genome and membrane.

Redox reactions in biology Aromatic compounds are reduced to form free radicals that contain one more electron than their parent compounds.

These anion free radicals reduce molecular oxygen to superoxide and regenerate the unchanged parent compound.

Redox reactions in biologyThe net reaction is the oxidation of the aromatic compounds and the reduction of oxygen to form superoxide

Free radicals in biology The two most important oxygen-centered free radicals are superoxide and hydroxyl radical.

Free radicals in biology Superoxide is biologically quite toxic and is deployed by the immune system to kill invading microorganisms, such as the intracellular killing of bacteria by neutrophile granulocytes.

Free radicals in biology

http://en.wikipedia.org/wiki/Neutrophile_granulocyte

Free radicals in biologySuperoxide radical Superoxide is also produced as a byproduct of mitochondrial respiration as well as several other enzymes.

Free radicals in biologyhttp://en.wikipedia.org/wiki/Electron_transfer_chain

Free radicals in biology Superoxide radical Superoxide is the anion O2. It is important as the product of the one-electron reduction of dioxygen. ex: O2 e O2

Free radicals in biologySuperoxide radical With one unpaired electron, the superoxide ion is a free radical . O2 e O2

ex: OO OO

Free radicals in biologySuperoxide radical 2 O2 + 2 H+ O2 + H2O2

(disprotionation)

Free radicals in biologyHydroxyl radical The hydroxyl radical, OH, is the neutral form of the hydroxide ion. Hydroxyl radicals are highly reactive and consequently short-lived.

Free radicals in biology Hydroxyl radical Most hydroxyl radicals are produced from the decomposition of hydroperoxides. ex: ROORperoxides ROOH hydroperoxides

Free radicals in biology Hydroxyl radical

2 H2O2 2 H2O + O2 (spontaneously) H2O2 UV 2 OH H2O2 biocatalyst 2 OH

Free radicals in biology Hydroxyl radical

H2O2 2 OH

HOOH 2 OH

Free radicals in biology Hydroxyl radical It can damage virtually all types of macromolecules: carbohydrates, nucleic acids, lipids and amino acids.

Free radicals in biologyOxidative stress is caused by an imbalance between the production of reactive oxygen and a biological system's ability to readily detoxify the reactive intermediates or easily repair the resulting damage.

Free radicals in biologyAll forms of life maintain a reducing environment within their cells.

This reducing environment is preserved by enzymes that maintain the reduced state through a constant input of metabolic energy.

Free radicals in biologyDisturbances in this normal redox state can cause toxic effects through the production of peroxides and free radicals that damage all components of the cell, including proteins, lipids, and DNA.

Free radicals in biologyMany forms of cancer are thought to be the result of reactions between free radicals and DNA.

The only means to protect important cellular structures is the use of antioxidants.

Antioxidants in biology Superoxide Dismutase (SOD) M(n+1)+-SOD + O2 Mn+-SOD + O2 Mn+-SOD + O2 + 2H+ M(n+1)+-SOD +H2O2 Total: 2 O2 + 2 H+ O2 + H2O2 where M = Cu ; Mn ; Fe ; Ni

Antioxidants in biology CatalaseH2O2 + Fe(III)-E H2O + O=Fe(IV)-E(+) H2O2 + O=Fe(IV)-E(+) H2O + Fe(III)-E + O2Total: 2 H2O2 2 H2O + O2

Where E = enzyme (porphyrin) in heme.

Antioxidants in biologyhttp://en.wikipedia.org/wiki/AntioxidantGlutathione

Antioxidants in biologyGlutathione disulfidehttp://en.wikipedia.org/wiki/Glutathione_disulfide

Oligomeric ProanthocyanidinsProanthocyanidin is also known as : procyanidin oligomeric proanthocyanidin, pycnogenol, leukocyanidin, leucoanthocyanin,is a class of flavanols.

Oligomeric ProanthocyanidinsOne was discovered in 1936 by Professor and called Vitamin P, although this name did not gain official category status and has since fallen out of usage.

Oligomeric ProanthocyanidinsProanthocyanidins are essentially polymer chains of flavonoids such as catechins.

Flavonoids C6-C3-C6

Flavonoidshttp://en.wikipedia.org/wiki/Flavonoid

Flavonoids

CatechinsEpicatechin, EC

CatechinsEpigallocatechin, EGC

CatechinsEpigallocatechin gallate , EGCG

Procyanidins

Oligomeric Proanthocyanidins

SED:,STT:LTT:

Conclusion(superoxide dismutaseSOD)(glutathione peroxidaseGPx)(catalase)

Conclusion

ConclusionSODcatalaseGPx

Thanks for your attention