2.4.4. Nitric oxide radical scavenging activity
Nitric oxide radical scavenging activity was determined according
to the method described by Sreejayan and Rao (1997). For the
estimation, 50 ll of sodium nitroprusside (SNP, 5 mM) was added
to 50 ll of various concentrations of the samples. Mixtures were
incubated under visible polychromatic light for 1 h, and then
100 ll of Griess reagent was added to the mixtures and incubated
for a further 5 min and the absorbance measured at 532 nm. Trolox
was used as the standard. To prepare Griess reagent an equal
amount of SA (1% sulphanilamide, 5% H3PO4) and NED (0.1%
N-(1-naphthyl)-ethylenediamine dihydrochloride (NED)) were
mixed. The nitric oxide scavenged (%) was calculated using following
formula:
Nitric oxide radical scavenged; % ¼ ½ðA0 A1Þ=A0 100;
where A0 is the absorbance of the control (dH2O), and A1 is the
absorbance of the extract/standard. A graph of nitric oxide radical
scavenged (%) vs. concentration of sample was plotted.