The hydroxyl radical-scavenging activity of SF extracts. The absorbance values were converted to the scavenging effect (%) and data plotted as the means of the replicate scavenging effect (%) values ± S.D. (n = 4). The IC50 value of the reference compound mannitol was 0.74 mg/ml. The concentration of SF extract was 20 mg of dried leaves/ml. (a: different from hot water extract, b: different from cold water extract, c: different from methanol extract, d: different from ethanol extract, e: different from acetone extract, p<0.05).