RESULTS AND DISCUSSION
In this study, several in vitro antioxidant assays were
performed, including scavenging of DPPH, superoxide
and hydroxyl radicals as well as reducing power.
Additionally, metal-chelating activity was also determined
by a ferrozine-Fe 2+ reaction system. Data on antioxidant
activities of HWEP are given in Table 1. The extract
showed antioxidant effects in all assays in a
concentration-dependent manner. DPPH radical
scavenging assay has been widely used to evaluate free
radical scavenging activity of natural antioxidants from
plant sources. The extract changed the violet color of
DPPH radical to yellow of non-radical DPPH-H form.
Interestingly, the DPPH radical scavenging activity of
HWEP (EC50 value=23.8±1.0 g/ml) was greater than the
positive control BHT (EC50 value=44.4±2.5 µg/ml),
whereas slightly less than ascorbic acid (EC50
value=13.0±0.2 µg/ml).