Reactive oxygen species production of the rotenone and 6-OHDA-induced differentiated SH-SY5Y cells. ROS was measured using a Fluorometric Intracellular ROS kit and was expressed as a percentage of the control cells’ production. (A) The cells were treated with rotenone for 24 h, followed by DMSO (in the case of Ctrl and Rot), linalool (Rot + Lin), geraniol (Rot + Ger), and rasagiline (Rot + Ras) for 24 h. (B) The cells were treated with 6-OHDA for 24 h, followed by DMSO (in the case of Ctrl and 6-OHDA), linalool (6-OHDA + Lin), geraniol (6-OHDA + Ger), and rasagiline (6-OHDA +Ras) for 24 h. (C) The cells were treated with ferric ammonium citrate (FAC) together with rotenone for 24 h, which was followed by DMSO (in the case of Ctrl, FAC, and FAC + Rot), linalool (FAC + Rot + Lin), geraniol (FAC + Rot + Ger), and rasagiline (FAC + Rot + Ras) for 24 h. (D) The cells were treated with ferric ammonium citrate (FAC) together with 6-OHDA for 24 h, which was followed by DMSO (in the case of Ctrl, FAC, and FAC + 6-OHDA), linalool (FAC + 6-OHDA + Lin), geraniol (FAC + 6-OHDA + Ger), and rasagiline (FAC + 6-OHDA + Ras) for 24 h. (E) The cells were pretreated with ferric ammonium citrate (FAC) for 24 h and then were treated with rotenone for additional 24 h, which was followed by DMSO (in the case of Ctrl, FAC, and FAC + Rot), linalool (FAC + Rot + Lin), geraniol (FAC + Rot + Ger), and rasagiline (FAC + Rot + Ras) for 24 h. (F) The cells were pretreated with ferric ammonium citrate (FAC) for 24 h and then were treated with 6-OHDA for additional 24 h, which was followed by DMSO (in the case of Ctrl, FAC, and FAC + 6-OHDA), linalool (FAC + 6-OHDA + Lin), geraniol (FAC + 6-OHDA + Ger), and rasagiline (FAC + 6-OHDA + Ras) for 24 h. The columns represent the mean value ± SD of three independent experiments. The number of technical replicates was four in each experiment. The asterisk shows p < 0.05 compared to the control. The cross indicates p < 0.05 compared to the rotenone or 6-OHDA treatments. The double cross signs indicate p < 0.05 compared to linalool and/or geraniol treatments.