**2.1 Endogenous antioxidants**

Endogenous antioxidants are divided into two classes, enzyme and non-enzymatic.

Endogenous antioxidants that are enzymes are: (1) Superoxide dismutase (SOD), (2) Glutathione peroxidase (GSH-PX), (3) Glutathione S-Transferases (GST), (4) Catalase (CAT), (5) Mitochondrial cytochrome oxidase system, (6) Hydroperoxidase [25, 26].

Non-enzyme endogenous antioxidants are: (1) Melatonin, (2) Ceruloplasmin, (3) Transferrin, (4) Myoglobin, (5) Hemoglobin, (6) Ferritin, (7) Bilirubin, (8) Glutathione, (9) Cysteine, (10) Methionine, (11) Urate, (12) Lactoferrin, (13) Albumin [26].
