GDNF and Parkinson disease: Previous studies have verified the protective effect of geraniol on PD animal models by alleviating a-Syn aggregation, maintaining the mitochondrial function, enhancing antioxidant, and restoring the generation of BDNF and GDNF (Rekha et al., 2013a; Rekha et al., 2013b; Rekha and Inmozhi Sivakamasundari, 2018).