Table 1.
Defence levels and mechanism of action of antioxidants.
| The first line of defence | The second line of defence | The third line of defence | |||
|---|---|---|---|---|---|
| Antioxidant | Mechanism of action | Antioxidant | Mechanism of action | De novo enzymes | Mechanism of action |
| Superoxide dismutase | O2•− → H2O2 | Ascorbic acid | Chain breaking: donate an electron to the free radical | Polymerases | DNA repair |
| Catalase | 2H2O2 → O2 + H2O | Uric acid | Glycosylases | ||
| Glutathione peroxidase | H2O2 + GSH → GSSG + H2O | Glutathione | Nucleases | ||
| Transferrin | Metal chelators or sequesters | α-Tocopherol | |||
| Caeruloplasmin | Ubiquinol | Proteinases | Protein proteolysis | ||
| β-Carotene | Incorporation of free radical | Proteases | |||
| Lycopene | Peptidases | ||||