Lipid peroxidation as a cause of ageing and injury of cells is
|A||Free radical theory|
|C||Enzyme cascade theory|
|D||Cell destruction theory|
Lipid peroxidation is a source of free Radicals:
a. Peroxidation (Atuo-oxidation) of lipids exposed to O2 is responsible for:-
i. Detrition of foods (Rancidity)
ii. Damage to tissues in vivo, where it may be a cause of cancer, inflammatory disease, atherosclerosis, aging etc.
iii. The deleterious effects are caused by free Radicals — eg. ROO°, RU°, OH° - produced during peroxide formation from fatty acids containing methylene-interrupted bonds (poly unsaturated F.A.)
b. Antioxidants: - control and reduce Lipid Peroxidation — eg.
i. Propyl glycol, Butylated hydroxyanisole and Butylated hydroxytoluene — used as food additives
ii. Vit. E (Tocopherol) — Naturally occurring Antioxidant
iii. Vit. C and Urate → Naturally occurring antioxidant
A. Betacarotene -4 an anti oxidant at Low PH
B. Lipid peroxidation is a chain reaction.
Antioxidants are two types according mode of action:
a. Preventive antioxidants (=reduce the rate of chain initiation): eg.
ii. other peroxidases
iii. chelators of metal ions - EDTA and DTPA
iv. Endogenous ceruloplasmin
b. Chain breaking antioxidants (=interfere with chain propagation): eg.
i. Superoxide dismutase
iv. Phenols or aromatic amines
v. Se-containing glutathione peroxidases.