Nitric oxide scavenging activity

The method described by Wintola and Afolayan[18] was used for the assay of the NO radical scavenging activity of the extracts. The procedure is based on the principle that sodium nitroprusside in aqueous solution at physiological pH spontaneously generates NO, which interacts with oxygen to produce nitrite ions. The nitrite ions are detected in solution by the Griess reagent which contains sulfanilamide and naphtylethylene diaminedihydrochloride. Compounds that scavenge NO compete with oxygen, leading to a reduced production of nitrite ions (Ebrahimzadeh et al.,[26]), For the essay, (0.5 ml of the extracts or standard was mixed with 2 ml of 10 mM sodium nitroprusside [prepared in 0.5 mM phosphate-buffered saline, pH 7.4]). The mixture was incubated for 2.5 h at 25°C. 0.5 ml of the mixture was mixed with 0.5 ml of Griess reagent (prepared by mixing 1 ml sulfanilic acid [0.33% in 20% glacial acetic acid] with 1 ml of naphthalene diaminedihydrochloride [0.1% w/v]). The mixture was incubated for 30 min at room temperature and the absorbance was measured at 540 nm. The percentage of NO scavenging ability of the plant extracts and standard compounds was calculated using the following formula: % NO scavenged = [(A_C–A_S)/A_C] × 100, where A_C is the absorbance of the control reaction and A_S is the absorbance of the test samples (extract or standard).