In PD, hesperidin has shown significant neuroprotective effects by intracellular calcium homeostasis, restoring dopamine levels, improved motor function, ameliorating oxidative stress and mitochondrial dysfunction, downregulating gsk3β, lrrk2, polg, and casp9 genes in 6-OHDA-toxicated SH-SY5Y cellular [132], and zebrafish model of PD [133], and iron-induced Drosophila model of PD [134]. This evidence concerns the gene CASP9 and Parkinson disease.