Embodiments of this invention provide methods for thereapeutic use of cyclic G-2-Allyl Proline to treat disorders of dopaminergic neurons, including Parkinson's disease. Cyclic G-2Allyl P is neuroprotective and has utility as a therapeutic agent for treatment of diseases and other conditions characterised by degeneration and/or death of dopaminergic neurons and the adverse symptoms of such degeneration and/or death. Such symptoms include loss of cognition and motor function. Compounds are also useful for manufacture of medicaments including tablets, capsules and injectable solutions that are useful for treatment of such conditions.