FREE RADICALS AND ANTIOXIDANTS – CURRENT STATUS A REVIEW I
DR T R RAMANUJAM M.D., C.MI.Biol (Lond)
WHAT ARE FREE RADICALS AND ANTIOXIDANTS
INVIVO ORIGIN OF FREE RADICALS
SOURCES OF OXIDATIVE STRESS IN HUMAN PATHOPHYSIOLOGY
MAJOR TARGETS OF OXIDATIVE ACTIVITY
INVIVO ORIGIN OF FREE RADICALS
Oxygenated Free Radicals
| O2.- | NADPH oxidation |
| Cytochrome oxidases | |
| Cytochrome P450 | |
| Xanthine oxidase | |
|
.OH X-Fe2 + H2O2 |
|
| ROO. | COX, LOX |
| PUFA | |
| RO. | ROOH |
| Free Radicals or – Pre Oxidents | Defense System |
| O2.- superoxide anion | Superoxide dismutaseMn SODCu, Zn SOD |
| .OH (Hydroxyl radical) | Vit C, Glutathoine Taurine, Uric acid |
| ROO. (peroxy radical) | Tocopherols Ubiquinone |
| 1o2 (singlet Oxygen) | Carotenoids |
| H2O2 (hydrogen Peroxide) | Catalase Se Glut peroxidase Glut reductase |
| ROO (hydroperoxides) | Se Glut peroxidase Glutathione reductase |
| Transition metals (Fe 2+, Cu+) | Chelators |
The defense systems – In addition to the continuous production of free radicals, our body possesses several defense systems that are constituted of enzymes and radical scavengers. These latter ones are easily oxidisable compounds which are present either in the cytosol (e.g.) ascorbic acid and glutathione) or in membranes (alpha tocopharols) The above table sums up these defense systems and their protective mechanisms.
These defense systems, called first line defense systems are not totally efficient, since almost all cell components undergo free radical damages. Therefore second defense systems are involved. They are constituted of repair systems for biomolecules that have been damaged by radical attacks.
