Medicinal Plants and Natural Products as Potential Sources for Antiparkinson Drugs

Parkinson's disease is a progressive neurodegenerative dysfunction characterized by the loss of pigmented dopaminergic neurons of the nigrostriatal system with a consequent dopamine decrease. The reduction of dopamine levels produces neuronal damage, depigmentation of the substantia nigra, and the presence of intracellular inclusions in dopaminergic neurons. Treatments for Parkinson's disease aim for improving these motor symptoms by increasing the dopaminergic signal in the striatum with levodopa in combination with enzyme inhibitors or anticholinergic drugs. Nevertheless, natural products can act as neuroprotective agents by reducing the progression of the disease and the inflammatory process. In the present review, we have compiled data on the principal medicinal plants and natural products as potential antiparkinsonian agents. They act by different mechanisms, such as the inhibition of alpha-synuclein condensation, reduction of oxidative stress and neuro-inflammation, increase of dopaminergic neurons survival, or the blockade of the A(2Ay) receptor.