Determination of superoxide anion scavenging
activity—The O2●- scavenging activity was evaluated
by measuring the reduction of NBT in a PMS-NADH
system, using the method slightly modified from
previously described21. Generation of the O2●- was
measured in the reaction mixture containing 20 of
TSCEs at various concentrations, 60 of 553
NADH, 60 of 143 NBT, and 60 of 9
PMS in 0.1 M phosphate buffer (pH 7.4), incubated at
room temperature for 8 min. The reduction of yellow
NBT to the purple formazan was measured by using a
microplate reader at 540 nm (Wallac 1420,
PerkinElmer Ltd, MN, USA). The O2●- scavenging
activity of TSCEs was calculated as the inhibition of
NBT reduction using the following equation: