Effect of isoquercitrin on glutathione peroxidase activity. The enzyme level was significantly higher in isoquercitrin pretreated samples. Glutathione peroxidase activity increased in a dose dependent manner. Data are mean and S.E. values from three independent experiments (n = 3). #p < 0.05, relative to control cells. *p < 0.05 and **p < 0.01, relative to cells treated only with 6-OHDA.