ABTS tests
The methoddeveloped by Muanda et al. (2010) was used in this
experiment; 1mM of AAPH solution was mixed with 2.5mM
ABTS as diammonium salt in phosphate buffered saline (PBS)
solution (100 mM, pH 7.4) containing 150 mM NaCl. After
incubation in a water bath at 68 °C for 20 min, the resulting
ABTS solution was diluted with the methanol to get blue-green
coloration with an absorbance of 0.70 ± 0.02 at 734 nm, then
2.94 mL of ABTS radical anion solution was added. The decrease of absorbance was measured at 734 nm. The radical stock
was prepared daily and all the tests were triplicated. The half
maximal inhibitory concentration (IC50), which refers to the
smallest concentration of antioxidants required to scavenge
50 % ofthe ABTS radical cation, was calculated.