Free radicals, especially reactive oxygen species like superoxide, hydroxyl, and perhydroxyl, can damage DNA, lipids, and proteins. This radical damage can lead to inheritable mutations, cancer, autoimmune diseases, and atherosclerosis. Sources of free radicals include ionizing radiation, transition metal ions, nitric oxide, the respiratory burst in immune cells, and mitochondrial electron transport. However, the body protects itself against radical damage through antioxidants like superoxide dismutase, catalase, glutathione peroxidase, vitamins C and E, and polyphenols; these antioxidants trap radicals in a stable form. At high concentrations, some antioxidants like vitamin C, vitamin E, and beta-carotene can also act

1. Free Radicals and Antioxidants
Dr.Herat soni
3rd
year resident
Biochemistry

2. Free radicals
The most damaging radicals in biological systems
are oxygen radicals (sometimes called reactive
oxygen species)—especially superoxide
hydroxyl, OH∙, and perhydroxyl, O2H∙.

3. Radical Damage
● DNA : Chemical changes
● Lipids :
Radical damage to Unsturated FA in cell
membrane and plasma lipoprotein
Lipid peroxides
Reactive dialdehydes
Chemically modify proteins and Nucleic acid
● Proteins :Tyrosine Residue , Cleavage of
peptide bond

4. Effects of radical damage
DNA
Inheritable mutation and cancer
Chemical modification of amino acid in protein
Auto immune Disease
Damage to plasma LDL
Atherosclerosis

6. Sources of oxygen radicals
● Ionising radiation
● Transition metal ions
● Nitric oxide
● Respiratory burst
● Mitochondrial oxidation of reduced flavins

7. Respiratory burst

8. Plasma free radical estimation
Lipid peroxides
Under acidic conditions, they oxidize Fe2+ to
Fe3+ , which forms a chromophore with
xylenol orange

9. Dialdehydes formed from lipid peroxides
Measured by reaction with thiobarbituric acid
they form a red fluorescent adduct—
Total thiobarbituric acid reactive substances,
TBARS.

10. Protection against Radical damage
● Metal ions as prostetic group
● Superoxide dismutase and catalase
● Glutathione peroxidase (Selenium)
● Vitamin E and Vitamin C
● Ascorbate , Uric acid and variety of polyphenols
Stable free radical trapping mechanism
● Ubiquinone and carotenes

12. Antioxidant can be pro-Oxidant
● Vitamin C
● Vitamin E
● Beta-carotene

13. Thank
you