Figure 2. Inhibitory effect of Polypodium leucotomos extract (PL) and kojic acid (KA) (0.0 to 1.0 mg/ml) on the reduction of nitroblue tetrazolium by superoxide anion radical (^·O₂^-) generated by the hypoxanthine-xanthine oxidase system. PL (gray bars), KA (black bars), and SOD (light gray bars) used as control.