Fig. 6. Cytoprotective effects of compounds 23, 25, 28 and 29 against H₂O₂-induced cell death on SH-SY5Y cells. Cell viability was measured by MTT assay and data were expressed as a percentage of viable cells (referred to control). Data is expressed as mean ± SD of three assays. ###P < 0.001 vs. the control group, *P < 0.05 vs. the H₂O₂ group treated with of H₂O₂ (400 μM) while **P < 0.01 and ***P < 0.001.