*2.5. Oxidative Stress and Antioxidant Status Markers*

#### 2.5.1. Catalase

The activity of catalase was measured in the whole blood using a UV-VIS spectrophotometer. The catalase enzyme extracts the peroxides from the region of the gel it occupies,

following the isolation of the native protein. The removal of peroxide does not cause potassium ferricyanide (yellow substance) to be reduced to potassium ferrocyanide, which reacts with ferric chloride to form a blue Prussian precipitate. The catalase positive control activity is defined in international unit equals (1 unit) to the amount of catalase necessary to decompose 1.0 μM of H2O2 per minute at pH 7.0 at 25 ◦C while H2O2 concentration falls from ≈ 10.3 mM to 9.2 mM. The absorbance of H2O2 decreases at 240 nm proportional to its decomposition so that the concentration of H2O2 is critical in this determination. The decrease in absorbance per time unit is the measure of catalase activity [25]. Results were expressed in U/g of Hb.
