Superoxide radical (•O2−) scavenging assay

The superoxide radical scavenging activities of sample was collected as previously described in Zhishen and Leong (Zhishen, Mengcheng & Jianming, 1999; Leong et al., 2008). Similarly, Vc was used as the standard antioxidant. L9F were separately dissolved in distilled water to prepare polysaccharide solutions of different concentrations 0.01, 0.02, 0.03 ... 0.09, and 0.10 mg/mL. A 1.0 mL sample of each concentration was mixed with 3.0 mL of Tris-Hcl buffer (pH 8.2), 0.8 mL of Pyrogallol (0.05 M). Then, the mixtures were bathed at 25 °C for 5 min and 1.0 mL HCl (8.00 M) was mixed after that. Finally, the absorbance was measured at 325 nm using a spectrophotometer.

Y is the •O²⁻ radical scavenging activity (%), A₁ is the absorbance of the sample and A₂ isthe absorbance of the control.