Parkinson^’s disease (PD) is an age-related CNS disorder characterized by depletion of dopaminergic neurons in the substantia nigra (SN) region of the brain, which leads to a marked decline of dopamine (DA) neurotransmitters in the striatum. Due to deficiency of DA supply to the striatum, an imbalance occurs between neurotransmitters acetylcholine (ACh) and dopamine (DA), subsequently resulting in classical PD symptoms manifested as tremor, akinesia, postural hypotension [1^-3]. The principal approaches applied in the management of PD symptoms by drugs that either prompt the release of dopamine or increase dopamine concentrations at receptors [4, 5]. Widespread downregulation of dopaminergic neurons increases with precarious onset in middle age to late adulthood. The mechanisms involved in the downregulation of dopaminergic neurons in PD patients are oxidative stress, mitochondrial dysfunction, neuroinflammation, excitotoxicity, imbalance of intracellular calcium, and iron homeostasis [6, 7]. Neurotoxin-based animal models have demonstrated themselves to be a reliable tool for investing in novel therapies and increasing the effectiveness of symptomatic treatment of PD [8]. The present therapeutic strategy against PD is mainly to restore the optimal dopamine(DA) level and its correlated signaling pathways in which levodopa, a precursor of dopamine(DA) is given to the PD patients [9]. Levodopa is given with carbidopa, a peripheral decarboxylase inhibitor that decreases the peripheral breakdown of L-Dopa and reduces the side effects of L-Dopa, mainly cardiovascular and gastrointestinal problems [10]. Another drug therapy for PD is monoamine oxidase B inhibitors(MAO-B), which inhibit DA metabolism which reinforces mitochondrial dysfunction and oxidative stress [11]. Further, a novel therapeutic option for PD is catechol-o-methyltransferase (COMT) inhibitors, which are administered with L-Dopa. COMT inhibitors prolong the action of L-Dopa, thus enhancing the duration of time a patient could take to benefit from L-Dopa [12, 13]. Another therapeutic approach for PD is dopamine receptor agonists, which directly stimulate the postsynaptic receptors in the striatum. They decrease the metabolism of dopamine and reduce free radical formation in the striatum [14]. Glutamate receptor antagonist is also given in PD, like amantadine, an antiviral drug that decreases motor and non-motor symptoms in PD patients, and akinesia is specifically treated by amantadine [15, 16].

Nowadays phytochemically active plant extracts and their secondary metabolites are being extensively used in PD therapy as these have substantial neuroprotective potential in PD [17]. Some important medicinal plants used in, which help in the mitigation of disease progression, are Ginkgo biloba, Bacopa monnieri, Curcuma longa, Camellia sinensis, green tea catechins, etc [9, 18^-21]. A study has shown that Mucuna pruriens contains Levodopa, which provides a long-term improvement in PD, with decreased risk of bradykinesia in the 6-OHDA lesioned model of PD [22], and has higher efficacy than levodopa [23].

Currently, the scientific community is focused on stem cell therapy for the treatment of PD. Stem cell transplantation is an easily accessible target for in vitro as well as in vivo systems. Neural stem cells have the innate ability to proliferate, migrate and differentiate into multiple cell lineages such as astrocytes, oligodendrocytes, and neuronal cells. A recent stu...