Neuroprotective effect of compounds 7a–d against toxicity induced by high OS in the SH-SY5Y neuroblastoma cell line. SH-SY5Y cells were treated with the corresponding compound (1 µM) during 24 h. Then, cells were treated with the corresponding compound and the rotenone (30 µM) and oligomycin A (10 µM) combination. Melatonin was included as positive control, and compounds CGP37157, rac-3a and (rac,R)-3b, R-6 and S-6 were included as reference and comparative purposes. Data were obtained from five experiments by duplicate, with normalized vs. basal condition considered as 100% cellular viability and expressed as mean ± SEM. Statistical analysis was performed by using one-way ANOVA, followed by Newman–Keuls post-test: ### p < 0.001 compared to basal; * p < 0.05, ** p < 0.01, *** p < 0.001 compared to toxic stimuli. Numerical data are given in Supplementary Materials Table S2.