1. The document discusses antioxidants and their role in the body. It describes how antioxidants mitigate the harmful effects of free radicals and lists some of the major antioxidant enzymes like superoxide dismutase, catalase, and glutathione peroxidase. 2. Antioxidants are classified based on their location in the body or plasma, cell membranes, intracellular spaces. They are also classified based on their nature as enzymatic or non-enzymatic antioxidants which include nutrient and metabolic antioxidants. 3. Important nutrient antioxidants discussed include vitamins C and E, carotenoids like beta-carotene and lycopene, selenium, and alpha-lipoic acid. Metabolic antioxid

1. GSVM MEDICAL COLLEGE
-PRESENTED BY NIDHI MAURYA
ROLL NO.- 138
UNDER THE GUIDANCE OF-
DR. JALAJ SAXENA SIR
HOD AND PROFESSOR
DEPARTMENT OF PHYSIOLOGY
ANTIOXIDANTS AND THEIR ROLE

2. ANTIOXIDANTS
To mitigate the harmful effects of free radicalsthe
aerobic cellshave developedantioxidantdefence
mechanism.A biologicalantioxidantdefined as
substancethat significantlydelays or inhibits
oxidation of substrate . Antioxidants may be
consideredas scavengersof free radicals.
The production of free radicalsand their
neutralisationby antioxidantsis normal bodily
process.

3. CLASSIFICATION OF ANTIOXIDANTS
1. .
1. Antioxidants according to their location
a) Plasma antioxidants:–β-carotene, ascorbic acid,
bilirubin, uric acid, ceruloplasmin, transferrin.
b) Cell membrane antioxidants:- α-toco-pherol.
c) Intracellular antioxidants:– superoxide dismutase,
catalase, glutathione peroxidase.

4. 2) Antioxidants according to their
nature and action
i) Enzymatic antioxidantse.g. superoxide
dismutase, catalase, glutathione peroxidase,
glutathione reductase.
ii) Non enzymatic antioxidants
a) Nutrient antioxidants
b) Metabolic antioxidant

5. THE ANTIOXIDANT ENZYME
SYSTEM
Superoxide
dismutase
First line of defense
to protect cells
from the injurious
effect of
superoxide
Catalase
Metabolises the
hydrogen peroxide
produced by SOD
Glutathione
peroxidase
It detoxifies H2O2 to H2O ,
while reduced glutathione is
converted to oxidised form. The
reduced glutathione can be
regenerated by glutathione
reductase utilising NADPH.

6. NUTRIENT ANTIOXIDANT
• Tocopherols [vitamin E] : vitamin E is a fat
soluble , and among the tocopherols, alpha-
tocopherol is biologically the most active. It is
an antioxidant present in all cellular
membranes, and protects against lipid
peroxidation.Alpha tocopherol can directly
act on oxyradicals and thus serves as an
important chain breaking antioxidant.

7. • Ascorbic acid: It is a vitamin that participates
in many metabolic reactions of the body and
is important water soluble antioxidant in
biological fluids.
• Vitamin C efficiently scavenges free radicals
and inhibits lipid peroxidation.
• It also promotes the regeneration of alpha
tocopherol from alpha toco-pheroxyl radical.

8. • Carotenoids : These are the natural compounds
with lipophilic properties. About 500 different
carotenoidshave been identified, among them
beta carotene is the most important .
• Beta carotene : Antioxidant under low partial
pressure of O2.
• Functions in associationwith vitamin C , E.

9. • Lycopene :
• Fat soluble pigment
• Responsible for colour to certain fruits and
vegetables e.g. tomato.
• Lutein and zeaxanthin impart yellow or green
colour . These pigments can also serve as
antioxidants.

10. • Selenium:
• Essential trace element
• Works with vitamin E in fighting free radicals
• Required for function of an important antioxidant
enzyme glutathione peroxidase.
• Alpha lipoic acid:
• It is vitamin like compound produced in body , besides
the supply from plant and animal sources.
• Recycling of other antioxidants such as ascorbic acid,
alpha tocopherol and glutathione.

11. Caffeine:
• Contains flavonoids[antioxidant]
Other nutrient antioxidants
• Proanthocynidinsof grape seeds
• Catechins of green tea
• Curcuminoids of turmeric
• Quercetin of onion

12. METABOLIC ANTIOXIDANT
Glutathione:
• Reduced glutathione[GSH] act as key role in biological
antioxidant enzyme system.
• GSH and H2O2 are the twin substrate for glutathione
peroxidase.
• GSH gets regeneratedfrom oxidised glutathione [GS-
SG] through the participation of glutathione reductase
and NADPH.
• Ability to synthesise GSH decreases as age advances
,and this have been implicated in certain diseases
e.g.cataract

14. Some more metabolic antioxidants of biological importance
• Uric acid : a powerful scavenger of singlet oxygen and OH-
radicals.
• Cerurloplasmin: inhibits iron and copper dependent lipid
peroxidation
• Transferrin: binds to iron and prevents iron catalysed free
radical formation.
• Albumin: can scavenge the free radicals formed on its
surface .
• Bilirubin: protects the albumin bound free fatty acids from
peroxidation.
• Haptoglobin: binds to free Hb and prevents the
acceleration of lipid peroxidation.

15. DIETARY SUPPLEMENTATION OF
ANTIOXIDANTS
Free radicals damage biomolecules such as
proteins, nucleic acids, lipids etc and are
implicated in the causationand progress of
several diseases [CHD , cancer , autoimmune
diseases].
To counter the action of free radicals , many
protective antioxidant nutrients (vit E and C,
beta carotene, selenium ) are in use as dietary
supplements.

17. Benefits of Antioxidants
1. Reduce the amount of free radicals in
your body.
2. Reduce the risk of developing certain
diseases such as; cancer, heart disease,
stroke, cataracts, Parkinson's, Alzheimer's
and arthritis.
3. Prevent direct cell damage caused by
the chain reaction that free radicals
initiate.
4. Reduce the signs of aging by preventing
the oxidation of your skin cells.
5. Improves digestion.
6. Relieves asthma and allergy symptoms.

18. RISKS OF ANTIOXIDANTS
• Even though there are many benefits to using
antioxidants, too much can also cause harm.
Too much antioxidant:
• Increase the risk of mortality.
• Increase the risk of cardiovascular disease.
• Increased risk of hemorrhagic stroke.
• The body produces its own antioxidants so
adding too many external antioxidants can
disrupt the homeostatic balance your body tries
to maintain which leads to complications.

20. Special thanks to-
Mahak Srivastava
Anshika Gautam