Oxidative stress and role of various antioxidants for better health

1. Division of BiochemistryDivision of Biochemistry
Rajah Muthiah Medical CollegeRajah Muthiah Medical College
Annamalai UniversityAnnamalai University

2. Molecules that protect tissues
from any free radical (molecule
with unpaired electron).
Organic molecule that Minimize
or prevent cellular damage
Numerous vitamins, minerals
phytochemicals and certain
enzymes

3. What are free radicals?What are free radicals?
Atom or group of atoms with an odd
(unpaired) number of electron
Capable of independent existence, but are
highly reactive
Initiates a chain reaction (dominoe effect)
Leads to disruption of a living cell
Overload of free radicals has been linked
to diseases including heart disease, liver
disease and certain cancers

4. Formation of free radicalFormation of free radical
Metabolism of oxygen by cells
form by products – free radicals
When the body breaks down
certain medications
Through pollutants
Oxygen molecule is a free radical

5. Free radical species of pathologicalFree radical species of pathological
importanceimportance
Super oxide ion O2
-
Hydroxyl OH-
Nitric oxide NO-
Ferryl ion FeO2+
Perferyl ion FeO2
2+
Allyl R
Alkoxyl RO.
Peroxyl ROO.
“R” is a polymer of – CH2- -CH=group

6. Role of transition metal inRole of transition metal in
free radical formationfree radical formation
Fenton’s Reaction
Fe2+
+ H2O2 Fe3+
+ OH + OH-
Presence of catalytic iron or copper
increases the rate of formation of free
radicals
Iron is carefully sequestered by a variety of
proteins

7. Iron sequestrationIron sequestration
Transferrin and haemopexin (during
transport)
Transferrin receptors (during uptake)
Ferritin and haemosidrin (during storage)

8. Role of free radicals inRole of free radicals in
respiratory burstrespiratory burst
Free radicals are generated by
neutrophils,monocytes, eosinophils
Used to kill internalized bacteria
after phagocytosis
This metabolic event is known as
respiratory burst

9. Activation of neutrophil NADPH – dependent oxidase
Formation of superoxide O2 - hydrogen peroxide
( formed from superoxide by SOD)
Fe3+ (catalyst)
MPO (myloperoxidase)
Formation of hydroxyl Radical (OH) HOcl (hypochlorous acid)
Destruction of internalized bacteria
Chronic granulomatous disease – NADPH oxidase system is defective
Repeated severe infections

10. Harmful effects of free radicalsHarmful effects of free radicals
• Free radicals are very unstable and highly
reactive
• Forms schiff’s bases and cause damage to DNA
• Lipid peroxidation - Peroxyl radicals
• In presence of Iron / copper ions
• Cytotoxic aldehydes (malondialdehydes and
hydroxy noneal)
• Chemicaly modify proteins and DNA
• May produce mutations or cancer

11. Antioxidants – Protection againstAntioxidants – Protection against
free radical damagefree radical damage
Antioxidants confer protection by safely
interacting with free radicals
Mode of action
Chelating the transitional metal catalysts
Chain breaking reactions
Reducing the concentration of reactive
radicals
Scavenging initiating radicals

12. AntioxidantsAntioxidants
Superoxide dismutase
Catalase
Enzymes Glutathione peroxidase
Natural – Vitamin E,
Vitamin C,
Selenium Carotenes
Non-enzymes
BHT
Synthetic
BHA

13. Enzymes (Cytoprotective enzymes)Enzymes (Cytoprotective enzymes)
1. Superoxide dismutase :
Zn/cu containign enzyme – cytosol
Manganese – metalloprotein – mitochondria
O2
-
+ O2
-
+ 2H+
H2O2 + O2
SOD
2. Catalase
Peroxisome and cytosol of the cell
2H2O2 H2O + O2
catalase

14. 3. Glutathione peroxidase
Selenium containing mettaloenzyme
H2O2 + 2GSH GSSG + 2H2O
Glutathione peroxidase
G.6.PD deficiency – Inability to form NADPH
causes hamolysis – hamolytic anaemia

15. Non-EnzymesNon-Enzymes
Tocopherols
Functions as a chain breaking
antioxidants
Anti cancer effect
Food source – Asparagus, corn oil,
hazel nuts, raw almonds, Soya
beans
RDA – Man 10 mg (15 IU)
Women 8 mg (12 IU)

16. Vit. C
Anti cancer effect
Combined action with tocopherols
Beneficial in smokers
Food source : Amla, guava, line, lemon,
green leafy vegetables
RDA – 60 – 70 mg /day
Additional requirement 20-40% more in
pregnancy in lactation

17. Carotenes
Scavengers of free radicals (alkoxyl and peroxyl)
Beta carotenes – lowers LDL cholesterol levels
Fodo soruce : Apricots, carrots, broccoli, mangoes,
peaches, peppers, pump kins
Astaxanthin – Fat soluble carotenoid – Fights
cancer and AMD
RDA – Man 1000 retional equivalent (5000 IU)
Women 800 retional equivalent (4000 IU)
1 retional equivalent = 6 µg of beta carotene

18. Glutathione
Inactivates hydrogen peroxide and lipid peroxides
Food source: Asparagus, Avacado
Selenium
Mineral forms a part of the enzyme glutathione
peroxidase that disposes free radicals
Food source : brazil nuts, sea food, organ meat

19. Spirulina
Microscopic, single cell blue – green algae
Food source: Available in form of pills, flakes (sprinkle over
salad) powder
Zinc (Zn)
Important component of enzymes
Food source: Eggs, meat, sea food, tofu
Flavanoid
Anti inflammatory plant antioxidant protects against heart
disease and cancer
Food source: Blue berries, carrots, egg plants, oranges
Protects ascorbic acid from being destroyed

20. Lutein
Found in eye’s retina, carotenoids slows progression of
AMD
Food source : broccoli, corn, egg yolk
Phytoestrogen
Iso flavones or natural plant estrogen
Food source: Green tea, grapes
N-Acetylcysteine (NAC)
Increases elvel fo glutathione
Food source: Eggs, granola, meats

21. Coenzyme Q10 : Also known as
ubiquinone
Lipid present in almost every plant and
animal
Prevents LDL cholesterol oxidation
Food Source: Broccoli, spinach, peanuts
Alpha lipoic acid : ALA
Prevents oxidation of LDL, protein and DNA
Food source: Beef, potato, spinach

22. Assessment of free radicalAssessment of free radical
damage and antioxidant statusdamage and antioxidant status
Protein oxidation
Detected by fluorescence spectroscopy
Lipid peroxidation
Diene conjucates : early marker of lipid
peroxidation 235 – 255 mm
Thiobarbituric acid
Absorbance measured at 532 nm or 553
nm

23. Estimation of Anti-oxidant statusEstimation of Anti-oxidant status
Assessment of cytoprotective
enzymes
a) Superoxide dismutase
b) Catalase
c) Glutathione peroxidase

24. Diets rich inDiets rich in
AntioxidantsAntioxidants
• Soya beans Green leafy vegetables
• Carrots Almonds
• Mangoes Amla
• Pumpkin Lemon
• Sea food Blue berries
• Oranges Green tea
• Grapes Peanuts
• Sunflower oil Corn oil

25. Wish youWish you
less oxidative stress
More antioxidants
Longer life
Thank You