Epigallocatechin-3-Gallate in Green Tea: A Promising Neuroprotective Agent Against Parkinson's Disease

Parkinson's Disease (PD) is the second most prevalent neurodegenerative disorder, marked by the progressive loss of dopaminergic neurons in the substantia nigra pars compacta and the presence of Lewy bodies. This neuronal degeneration leads to motor symptoms such as tremors, rigidity, and bradykinesia. Neurochemical alterations, including mitochondrial dysfunction and oxidative stress, are critical in the pathogenesis of PD. With an aging global population, the prevalence of PD is expected to reach 9 million by 2030. Green tea, from Camellia sinensis, is widely consumed for its health benefits, including its neuroprotective properties. Its key component, (-)-epigallocatechin-3-gallate (EGCG), is noted for its potent antioxidant, anti-inflammatory, and neuroprotective activities. EGCG provides significant neuroprotection against MPTP-induced neurotoxicity, a model for Parkinsonism, by inhibiting inducible nitric oxide synthase (iNOS) and neuronal nitric oxide synthase (nNOS), reducing nitric oxide (NO)-mediated oxidative stress. It also preserves dopaminergic neurons and maintains dopamine levels in the striatum. Against 6-OHDA-induced neurotoxicity, which mimics PD, EGCG regulates iron metabolism by modulating iron regulatory proteins. It enhances dopaminergic neuron survival and neurite outgrowth by stabilizing mitochondrial function and controlling the ROS-NO pathway. This review mainly focuses on significant neuroprotective effects of EGCG against neurotoxins like MPTP and 6-OHDA, reducing oxidative and nitrosative stress, regulating iron metabolism, and stabilizing mitochondrial function. These findings highlight the potential of green tea and EGCG in developing treatments for PD and other neurodegenerative disorders.