Both the bioactives levodopa and 6,7-dimethoxy-1,2,3,4-tetrahydroisoquinoline-3-carboxylic acid of Mucuna prurines are predominant [20], levodopa is considered to be the major bioactive of the M.prurines; and the other natural bioactive, 6,7-dimethoxy-1,2,3,4-tetrahydroisoquinoline-3-carboxylic acid isolated from Mucuna pruriens, traditionally used for the treatment of Parkinson's disease, and synthesized from l-DOPA, behaves as a peripheral catechol-O-methyltransferase inhibitor. This evidence concerns the gene COMT and Parkinson disease.