08-16-2013, 12:44 AM
Antioxidants are capable of stabilizing, or deactivating, free radicals before they attack cells. Antioxidants are absolutely critical for maintaining optimal cellular and systemic health and well-being.
They can be classified in to a variety of categories depending on the basis of solubility, mode of action etc.
On the basis of solubility
(a). Hydrophilic antioxidants:- They are soluble in water. Water soluble antioxidants react with oxidants react with oxidants in the cell cytoplasm and blood plasma.
(b). Hydrophobic antioxidants:- They are soluble in lipids. Lipid soluble antioxidants protect cell membranes from lipid peroxidation.
On the basis of line of defense
(a). First line defense (preventive antioxidant):- They intercept the free radicals or sequester them before any damage can be done. They work in one out of three ways – deactivating metals (transferring) , quenching superoxide ions ( bilirubin) and removing hydroperoxidases(catalase) . E.g. Superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GTX), glutathione reductase.
(b). Second line defense (Radical scavenging antioxidant):- These are basically chain breaking antioxidants that react with peroxyl radicals . Their mode of action can be as a donor molecule ( ascorbic acid) or as a sacrificial antioxidant ( uric acid). Examples include tocopherol, glutathione, etc. In order to be a good chain breaking antioxidant it is essential that the antioxidant decay be harmless, recyclable and it shouldn’t react with singlet oxygen itself to form a peroxyl radical.
(c ). Third line defense (Repair and de-novo enzymes):- These are a group of enzymes for repair of damaged DNA, protein, oxidized lipids and peroxides. These enzymes repair the damage to biomolecules and reconstitute the damaged cell membrane. Examples include involved in DNA damage repair, cancer and aging.
(d) Fourth line defense ( enzyme inhibitor antioxidant) :- It basically involves those antioxidants that are involved in an adapted mechanism in which a signal responsible for free radical production and reaction is utilised to prevent its formation or reaction. The signal generated from the free radical formed acts as a guide and brings the antioxidant to the right site.
They can be classified in to a variety of categories depending on the basis of solubility, mode of action etc.
On the basis of solubility
(a). Hydrophilic antioxidants:- They are soluble in water. Water soluble antioxidants react with oxidants react with oxidants in the cell cytoplasm and blood plasma.
(b). Hydrophobic antioxidants:- They are soluble in lipids. Lipid soluble antioxidants protect cell membranes from lipid peroxidation.
On the basis of line of defense
(a). First line defense (preventive antioxidant):- They intercept the free radicals or sequester them before any damage can be done. They work in one out of three ways – deactivating metals (transferring) , quenching superoxide ions ( bilirubin) and removing hydroperoxidases(catalase) . E.g. Superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GTX), glutathione reductase.
(b). Second line defense (Radical scavenging antioxidant):- These are basically chain breaking antioxidants that react with peroxyl radicals . Their mode of action can be as a donor molecule ( ascorbic acid) or as a sacrificial antioxidant ( uric acid). Examples include tocopherol, glutathione, etc. In order to be a good chain breaking antioxidant it is essential that the antioxidant decay be harmless, recyclable and it shouldn’t react with singlet oxygen itself to form a peroxyl radical.
(c ). Third line defense (Repair and de-novo enzymes):- These are a group of enzymes for repair of damaged DNA, protein, oxidized lipids and peroxides. These enzymes repair the damage to biomolecules and reconstitute the damaged cell membrane. Examples include involved in DNA damage repair, cancer and aging.
(d) Fourth line defense ( enzyme inhibitor antioxidant) :- It basically involves those antioxidants that are involved in an adapted mechanism in which a signal responsible for free radical production and reaction is utilised to prevent its formation or reaction. The signal generated from the free radical formed acts as a guide and brings the antioxidant to the right site.
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