A study using high throughput drug screening, whose aim was to identify disease-modifying compounds for Parkinson's disease, also showed that a series of natural triterpenes, such as ursocholanic acid and ursolic acid, significantly increased the activity of all four complexes of the mitochondrial respiratory chain and preserved intracellular ATP levels in parkin (PARK2) mutant fibroblasts [58]. This evidence concerns the gene PRKN and Parkinson disease.