This assay detects scavenging of free radicals by the tested compound
through the scavenging activity of the stable 2, 2-diphenyl-
1-picrylhydrazyl (DPPH) free radical. This assay was performed
using a previously described method (van Amsterdam et al.,
1992) with some minor modifications. Briefly, 25 ll of tea extract
was allowed to react with 250 ll of 0.2 mM DPPH in 95% ethanol
in a 96-well microplate. The plate was then incubated at 37 C
for 30 min after which the absorbance was measured at 550 nm
using a microplate reader. Scavenging capacity of the sample was
compared to that of ascorbic acid as a positive control (0.1–
1.0 mM ascorbic acid).