*2.15. Superoxide Dismutase (SOD) Activity*

Total SOD activity was assessed as previously described [29], based on SOD inhibiting the reduction of nitro blue tetrazolium (NBT) by O2 •−. Epimastigote cells were harvested by centrifugation, washed three times in cold PBS, and disrupted by freeze-thaw. Centrifugation as described above was used to collect epimastigote cells, which were washed three times in cold PBS and disrupted by freeze-thaw. The Bradford method [42] was used to determine the protein content in the whole homogenate. In a final volume of 200 μL, the homogenates (using known amounts of protein in the range of 10–50 μg) were incubated in a reaction medium containing 45 mM potassium phosphate buffer (pH 7.8), 6.5 mM EDTA, and 50 mM NBT. The reaction began with the addition of 2 mM riboflavin. The sample's absorbance at 560 nm was measured after 15 min in a lightbox. SOD activity was expressed as the quantity of enzyme-blocking NBT reduction by 50% for each amount of protein.
