free radical scavengers.pdf

reaction of scavengers it is very useful. it helps to undersrand the reaction.

1. Reaction Intermediate
Free Radical Scavangers

2. Definition
A free radical is a molecule or molecular
fragment that contains one or more unpaired
electrons in its outermost orbital.
Free radical is generally represented by
superscript dot.

4. Properties of free radicals
oThey are electrically neutral and carries no
charge
oHighly reactive
oParamagnetic
oCarbon atom in free radical is sp
2
hybridized
oThey are stabilized by resonance

5. Generation
Methods of preparation:
1- Photolysis
2- Thermolysis
3- Oxidation reduction reactions

6. 1-Photolysis

7. 2-Thermolysis
Compounds containing weak bonds often
produce free radicals when subjected to
heat.

8. 3-Redox reactions

9. Mechanism of Free Radicals

11. 1- Addition
Tetrachloroethylene

12. 2- Displacement

13. 3- Rearrangement
3,3 diphenyl butyric acid

14. Free radical scavengers
free radical scavengerA substance,
also known as antioxidant, that helps
protect cells from the damage caused
byfree radicals.
Free radicalsare unstable molecules
that are made during normal cell
metabolism

17. Applications of free radical
scavengers
Glutathione peroxidase (enzyme)
which reduces H2O2 to H2O.
Vitamin E (alpha tocopherol) prevent
the peroxidation of membrane
phospholipids and avoid cell membrane
damage through its antioxidant action.
Vitamin E known as ‘chain breaking
antioxidant’ , It also stimulates the immune
response.

18. Beta carotene is precursor of vitamin A
and also have antioxidant effects, it also
protect cell membrane lipids from harmful
effects of oxidative degradation.
Melatonin is a hormone and is scavenger
of free radicals mainly of OH radicals.
Selenium is a trace element which
enhances the antioxidant activity of
Vitamin E
Polyphenolic antioxidants (flavanoids)
also possess good antioxidant activity

19. Vitamin C (ascorbic acid) directly
scavanges O2, H2O2 , OH , it also
contributes to Vit E generation.
• Garlic, grape fruit, soya bean, tumeric,
tomato have excellent radical scavenging
activity

20. Uric acid also plays role in scavenging the
OH radical in body.
Albumin can scavenge the free radical
forming on its surface.
Antioxidants are also helpful in
preventing cancerand neutralizes the
substance that damages genetic material.