Scavenging activities of the purified compounds towards hydroxyl radical is measured by Co (II) EDTA-induced luminol chemiluminescence by flow injection method which based on the catalytic oxidation of hydrogen peroxide by luminol-H2O2-Co (II)-EDTA system, forming a hydroxyl radical flux that can produce a stable chemiluminescence signal which is attenuated in the presence of antioxidants. As shown in Figure 3C and Table 1, the hydroxyl radical scavenging activity of the tested compounds decreased in the order of: 2 > 3 > 1 > 4, which was consistent with the results of the DPPH and ABTS assays.