2.6.1.3. Nitric oxide radical scavenging activity
Nitric oxide (NO) generated from sodium nitroprusside was measured by the Griess reaction [20]. Sodium nitroprusside (5μM) in phosphate-buffered saline was mixed with 3 mL of different concentrations (10–500 μg/mL) of A. squamosa extracts and the mixture was incubated at 25°C for 150 minutes. The samples were then allowed to react with the Griess reagent (1% sulfanilamide and 0.1% naphthyl ethylenediamine dihydrochloride in 2% H3PO4). The absorbance of the chromophore during the diazotization of nitrite with sulfanilamide and subsequent coupling with naphthyl ethylenediamine was measured at 546 nm. A similar procedure was repeated with respective solvent instead of the extract, which served as the control; l-ascorbic acid (5–250 μg/mL) was used as the positive control [21]. All the tests were performed in triplicate. The percentage of scavenging activity was measured using the formula mentioned in the “Radical Scavenging Activity” section.