ANTIOXIDENTS

DEFINITION:
Antioxidants are often described as “free radical scavengers” meaning that they neutralize the electrical charge and prevent the free radicals from taking electrons from other molecules. They play a key role in the body defense system against reactive oxygen species (ROS) which are known to be involved in the pathogenesis of aging and many degenerative diseases such as cardiovascular diseases,cataract and cancers atherosclerosis, hypertension, ischemia/reperfusion injury, diabetes mellitus, neurodegenerative diseases (Alzheimer's disease and Parkinson's disease), rheumatoid arthritis, and ageing.
To protect the cells and organ systems of the body against reactive oxygen species, humans have evolved a highly sophisticated and complex antioxidant protection system. It involves a variety of components, both endogenous and exogenous in origin, that function interactively and synergistically to neutralize free radicals. These components include:

ANTIOXIDENTS IN ANIMALS
Endogenous Antioxidants
• Bilirubin
• Thiols, e.g., glutathione, lipoic acid, N-acetyl cysteine
• NADPH and NADH
• Ubiquinone (coenzyme Q10)
• Uric acid
• Enzymes:
– copper/zinc and manganese-dependent superoxide
dismutase (SOD)
– iron-dependent catalase
– selenium-dependent glutathione peroxidase
Dietary Antioxidants
• Vitamin C
• Vitamin E
• Beta carotene and other carotenoids and oxycarotenoids,
e.g., lycopene and lutein
• Polyphenols, e.g., flavonoids, flavones, flavonols, and
proanthocyanidins
Metal Binding Proteins
• Albumin (copper)
• Ceruloplasmin (copper)
• Metallothionein (copper)
• Ferritin (iron)
• Myoglobin (iron)
• Transferrin (iron)



There are two lines of antioxidant defense within the cell. The first line, found in the fat soluble cellular membrane consists of vitamin E, beta-carotene, and coenzyme Q. Of these, vitamin E is considered the most potent chain breaking antioxidant within the membrane of the cell. Inside the cell, water soluble antioxidant scavengers are present. These include vitamin C, glutathione peroxidase, superoxide dismutase (SOD), and catalase .
Plant cells are known to have both enzymatic and non-enzymatic defense mechanisms to counteract the destructive effects of activated oxygen species. The antioxidant defense system consists of low molecular weight antioxidants such as ascorbate, glutathione, a-tocopherol and b-carotenoids, peptides, vitamins, flavonoids, phenolic acids, alkaloids as well as several antioxidant enzymes such as superoxide dismutase (SOD), guaiacol peroxidase (POD), ascorbic acid peroxidase (APX) and glutathione reductase (GR)

ANTIONIDNTS IN PLANTS
ENZYMATIC:
Oxido reductase
Catalases
superoxide dismutases
guaiacol peroxidase (POD),
ascorbic acid peroxidase (APX)
glutathione reductase.
Non-enzymatic:
Nutrient:
ascorbate
glutathione
a-tocopherol
b-carotenoids
Non-nutrient:
Flavonoids
Phenolic acids
Alkaloids
BHA (butylated hydroxyanisole)
BHT (butylated hydroxytoluene).