DPPH radical scavenging assay
A fi nal concentration of 0.6 mM methanol solution of
DPPH in sample was 0.02 mM. Final concentration of extracts
(previously dissolved in water) was 0.1 mg/mL. Sample
with no extract served as a control. Each preparation was
incubated for 20 minutes at room temperature (20 oC), and
then measurements involving 4 minutes scanning time were
conducted. The EPR spectra were recorded on Varian E104-A
EPR spectrometer. EPR measurements were performed using
parameter modulation amplitude, 1 G; modulation frequency,
100 kHz; microwave power, 10 mW; time constant, 0.032
s; fi eld centre, 3370 G; scan range, 40G. All experiments
were performed fi ve times and presented as means ± S.D.
The amplitude (A) of the middle peak in the EPR signal was
measured, and antioxidative activity (AA) of each extract was
calculated using Eq. 1:
AA = (Acontrol – Aextract)/ Acontrol