Neuroprotective role of polyphenols against oxidative stress-mediated neurodegeneration.

Neurodegenerative diseases (NDs) are characterized by disorders with progressive deterioration of the structure and/or function of neurons. Genetic mutations can lead to many NDs. Nevertheless, neurodegeneration can also take place due to several biological processes. The pathogenesis of several NDs including Alzheimer's (AD), Parkinson's (PD), and Huntington's (HD) diseases are associated with oxidative stress (OS). In order to maintain the normal functions of neurons, lower levels of reactive oxygen species (ROS) and reactive nitrogen species (RNS) are important, since their increased levels can cause neuronal cell death. It has been found that OS-mediated neurodegeneration involves a number of events including mitochondrial dysfunction, Ca2+ overload, and excitotoxicity. A growing number of studies are suggesting the benefit of using polyphenols for the treatment of neurodegenerative disorders. Indeed, in order to treat most of the NDs, synthetic drugs are extensively used which are found to exert side effects in the course of the treatment. There is mounting evidence that researchers have identified several naturally-occurring chemical compounds in plants, which are used for the management of NDs. Overall, polyphenolic phytochemicals are safer in nature and have negligible side effects. In this article, we have focused on the potential efficacy of polyphenols such as epigallocatechin-3-gallate, curcumin, resveratrol, quercetin and methylated polyphenols berberine against the most common neurodegenerative disorders.