3.2. Free-radical-scavenging activity (DPPH* and ABTS+* assays)
Free-radical-scavenging activities of O. narbonense extracts
were assessed by DPPH* and ABTS+*. The results were expressed
as trolox equivalents (mg TEs/g extract) and are summarized in
Table 1. Both DPPH* and ABTS+* measure reductions of radical
solutions in the presence of a hydrogen-donating antioxidant. The
results of both assays found the Bulb-EA extract to exhibit the
most activity (18.16mgTEs/g extract for DPPH*, 30.32mgTEs/g
extract for ABTS+*) and the S-EA extract to exhibit the least activity.
The strong free-radical activity of the Bulb-EA extract can be
explained by the high levels of phenolic substances. The results of
this study suggest that free-radical-scavenging activity positively
correlates with the phytochemical constituents of the extracts
studied. Similarly, previous reports have shown phenolic compounds
to contribute significantly to the antioxidant activity of
medicinal plants (Lim et al., 2009; Zhao et al., 2010).