Free radicals are molecules with unpaired electrons that can damage cells. They are generated through normal cell processes but also environmental exposures. Antioxidants protect against free radical damage by neutralizing them. There are two main classes of antioxidants - enzymatic and non-enzymatic. Enzymatic antioxidants include superoxide dismutase and catalase while non-enzymatic antioxidants include vitamins C and E, carotenoids, and polyphenols. These antioxidants help prevent chronic diseases associated with oxidative stress and aging.

1. FREE RADICALS
AND
ANTIOXIDANTS

2. Oxidants and antioxidants
•Free radicals: free radical is a molecule or
molecular fragment that contain one or more
unpaired electrons in the outer orbital
•They are also known as reactive oxygen species
( ROS)
•Examples are: superoxide, singlet oxygen,
H2O2, peroxynitrite, NO, OH, ROO

3. Generation of free radicals
•Leakage from mitochondrial electron
transport: mitochondria is the major site
for production of superoxide ions.
•Mitochondria also has high levels of GPx
and GSH
•Xanthine oxidase: in the metabolism of
purine
•NADPH oxidase: in inflammatory cells like
neutrophils, macrophages, on phagocytosis, there is
respiratory burst.

5. •Superoxide ions are produced due to
respiratory burst: it is then converted
to H2O2 and hypochlorous acid which
kill the bacteria
• This mechanism is deficient in chronic
granulomatous disease

6. •Nitric oxide synthase: from arginine NO is
produced
•Lipooxygenase: for synthesis of leukotrienes
Physical agents:
•UV rays
•Ionising radiation
•Cigarette smoke
•Air pollutants

7. Clinical significance
•Chronic inflammation: ROS is associated with
tissue damage and implicated in pathogenesis of
chronic ulcerative colitis and chronic
glomerulonephritis
•Acute inflammation: activated macrophages
produce free radicals
•Respiratory diseases: Adult respiratory distress
syndrome, bronchopulmonary dysplasia
•Eye: retrolental fibroplasia, cataract

8. •Reperfusion injuries
•Atherosclerosis and myocardial
infarction: oxidation of LDL: formation
of foam cells
•Skin diseases: psoriasis
•Cancers due to mutation
•Ageing.

10. Lipid peroxidation

11. Free radical scavenger system
Antioxidants:
These are compounds that protect
the cells from the damaging effects
of free radicals

12. CLASSIFICATION OF
ANTIOXIDANTS

14. 2. According to the mode of action

19. Vitamin C ( ascorbic acid)
•Scavenges water soluble peroxyl and
perhydroxyl , superoxide, hypochlorous acid and
singlet oxygen
•Prevents fenton reactions : decreases heme
breakdown
•Re forms alpha tocopherol
•Protects against ROS from cigarette smoke

21. Alpha Tocopherol
•Lipid soluble antioxidant
•Protects the cell membrane ( membrane integrity)
•Requires coenzyme Q10 for regeneration
•Antioxidant and anti inflammatory
•Prevents release of NO from vascular endothelium
•Prevents platelet aggregation
•Prevents relase of superoxide radicals form
macrophages

22. Carotenoids
•These are available in deep orange red colour
vegetables and fruits like carrot, tomatoes, water
melon ,red grapes etc
•These are also known as tetraterpines
•600 variants are known
•Beta carotene, alpha carotene, lycopene, retinol
etc
•Lycopenes are twice as effective as beta carotene
•They protect against lung, stomach and prostate
cancers

23. Polyphenols
•Dietary polyphenols are found in fruits, tea,
chocolates.
•They contain flavones, isoflavones, flavonols,
catechins and phenolic acids
•They have anti oxidant, anti apoptotic,
antiaging, anti inflammatory anti carcinogenic
properties.
•They are protective against cardiovascular
diseases.

24. Superoxide dismutase