The neuroprotection mechanisms of oleuropein, purified from Olea europaea leaf, increased cell viability and decreased biochemical markers of cell death, intracellular ROS level, Bax/Bcl-2 protein ratio, cleaved caspase-3 activation, and DNA fragmentation in PC12 cells exposed to 6-OHDA in Parkinson’s disease research (Shahpiri et al., 2016). This evidence concerns the gene CASP3 and Parkinson disease.