Dopamine and central dopaminergic circuitry in neurodegenerative diseases: Roles and mechanisms of action of natural phytochemicals

There has been increasing effort in the research and development of dopamine neurotransmission as an early clinical marker for neurodegenerative diseases, namely Parkinson’s and Alzheimer’s disease in recent years. Given the side effects and clinical performances of some approved dopaminergic drugs, there is a growing interest in exploring the neuroprotective properties of medicinal plants as alternatives. Although not curative, these phytochemical compounds show potential in protecting and maintaining the integrity and functions of dopaminergic neurons, thereby mitigating neurological symptoms. This review highlights medicinal plants and their bioactive compounds with neuroprotective effects on the dopaminergic system of the human brain, particularly focussing on their mechanism of actions, potentials and challenges as alternative therapeutics.