Chapter 25 - Green and black tea in brain protection

Abstract

Several lines of evidence suggest that enhanced reactive oxygen species (ROS) generation and a decrease in antioxidative abilities are the reasons for oxidative stress (OS) followed by subsequent inflammation, which plays a pivotal role in neurodegenerative disorders such as Parkinson's disease (PD) and Alzheimer's disease (AD). Thus, antioxidative defense is critically important in nervous tissue protection. Several potent antioxidants, especially those belonging to natural products, have been investigated. One such potentially health promoting beverage is tea, especially green tea whose components, mainly catechins and catechin derivates, have proven antioxidant properties. The protective effects of green tea extract on the central nervous system tissue expression in decreased levels of lipid peroxidation products have been shown. A large study investigating PD found a moderate risk reduction in tea consumers compared to non-tea drinkers. However, the investigations of the past few years show that black tea components also possess antioxidative properties, which have been proven in vitro as well as in vivo experiments. The specific mechanisms by which tea polyphenols exert their neuroprotective action are not clearly defined. However, recent evidence indicates that besides their antioxidant and iron chelating properties, polyphenols have a profound effect on cell survival/death genes and signal transduction. The revelation of novel molecular targets possibly implicated in their neuroprotective action include calcium homeostasis, the extracellular mitogen-activated protein kinases (MAPK), protein kinase C (PKC), antioxidant enzymes, antioxidant regulatory element (ARE) survival genes, and processing of the amyloid precursor protein (APP) pathway.