The DPPH free radical is a stable free radical, which has been
widely accepted as a tool for estimating the free radical-scavenging
activity of antioxidant (Nagai, Inoue, Inoue, & Suzuki, 2003). In the
DPPH test, the antioxidants were able to reduce the stable DPPH
radical to the yellow-coloured diphenylpricryhydrazine. The effect
of antioxidant on DPPH radical scavenging was conceived to their
hydrogen-donating ability (Chen, Xie, Nie, Li, & Wang, 2008).
The result of DPPH free radical-scavenging ability of the essential
oil is shown in Fig. 3 and compared with ascorbic acid as control
standards. As can be seen from Fig. 3, the DPPH radical scavenging
increased from 33.1% to 61.6%, when the concentration of the
essential oil increased from 0.2 to 1.0 mg/mL. The IC50 of the
essential oil and Vc were 0.63 and 0.27 mg/mL, respectively. The
results indicated that the essential oil exhibited a potential DPPH
radical scavenging activity.