Table 2.

Major antioxidants.

	Name	Role	Remarks
Endogenous enzymes	Superoxide dismutase (SOD) (a) mitochondrial (b) cytoplasmic (c) extracellular	Dismutase superoxide to H2O2	(a) Contains manganese (MnSOD) (b) Contains copper and zinc (CuZnSOD) (c) Contains copper (CuSOD)
	Catalase	Dismutase H2O2 to H2O	Present in peroxisomes
	Glutathione peroxidase	Removes H2O2 and lipid peroxides	Selenoproteins (contains Se2+) Primarily in the cytosol also mitochondria
	Vitamin E	Lipid peroxidation, scavenges superoxide, hydroxyl and lipid peroxide	Fat soluble
Nonenzymatic substance	Vitamin C	Scavenges superoxide, hydroxyl radicals and H2O2, contributes to regeneration of vit E. Neutralizes oxidants from stimulated neutrophils	Water soluble
	β-carotene (provitamin A)	Scavenges  ·OH, O2·− and peroxy radicals Prevents oxidation of vitamin A Binds to transition metals	Water soluble