Analysis of activity of catalase (CAT), glutathione reductase (GSH), superoxide dismutase (SOD), and glutathione peroxidase (GPx). The activity of CAT, GSH, SOD, and GPx was decreased in PoTwS cells compared to PC12 cells. Meanwhile, the PC12+syn++sep−+hydroxytyrosol cells line displayed the highest CAT and GSH activity compared to PoTwS cells. The description of each cell line is given in Supplementary Table S3. Data are mean and S.E. values from three independent experiments (n = 3). # p < 0.01, relative to PC12 (control cells). * p < 0.05 and ** p < 0.01, relative to the cells treated only with salsolinol.