Effect of isoquercitrin on catalase activity. Isoquercitrin showed a significant increase in the catalase activity in all pretreated cells in a dose dependent pattern. The greater activity of catalase was seen after 4 and 12 hours. Data are mean and S.E. values from three independent experiments (n = 3). #p < 0.01, relative to control cells.*p < 0.05, **p < 0.01 and ***p < 0.001, relative to cells treated only with 6-OHDA.