SNCA and Parkinson disease: Together with other bioactive substances from the body wall and Cuvierian tubule of H. leucospilota, saponin-rich extract improved DA neuronal function in food-sensing behavior and reduced α-synuclein aggregation, which in turn promoted the neuroprotection and regeneration of DA neurons in 6-OHDA-treated C. elegans PD models by downregulating the apoptosis gene (egl-1) and upregulating the genes that govern DA-synthesis (cat-2) and free-radical scavenging (sod-3) [65].