Nitric oxide radical scavenging assay

The procedure is based on the principle that sodium nitroprusside in aqueous solution at physiological pH spontaneously generates nitric oxide (NO) which interacts with oxygen to produce nitrite ions that can be estimated using Griess reagent (Ebrahimzadeh et al. 2009). Scavengers of NO compete with oxygen, leading to reduced production of nitrite ions. Each sample solution (2 mL) was mixed with sodium nitroprusside (4 mL of 10 mM, in PBS pH 7.4), and incubated at room temperature for 150 min. After the incubation period, 0.5 mL of Griess reagent was added. The absorbance of the chromophore formed was measured at 546 nm. AA and BHT were used as standard. The NO scavenging activity was calculated using the following equation (2):