Epigallocatechin gallate (EGCG) is a phytochemical found in green tea. Green tea, a popular beverage produced from the leaves of the Cammelia sinesis plant, is made up of several chemical compounds called polyphenols. Polyphenols are naturally occurring compounds found in most plant-derived foods with tea, red wine, fruits, and vegetables among the richest dietary sources. Polyphenols can be divided into three classes: tannins, lignins, and flavonoids. The polyphenols in tea are classified as flavonoids. Flavonoids are distinguished by their chemical structure under the categories: anthocyanidins, carotenes, catechins, flavones, flavonols, flavanones, glucosinolates, isoflavones, lavones, and organosulfides. The major flavonoids in tea are catechins. In green tea the catechins account for 30%-40% of the contents in a normal tea bag. Catechins are present in higher quantities in green tea than in black or oolong tea. This is because during processing green tea is exposed to the least amount of oxidation. The catechins in green tea include epicatechin (EC), epigallocatechin (EGC), epicatechin gallate (ECG), and epigallocatechin gallate (EGCG). EGCG is the most abundant catechin found in green tea and accounts for 65% of the total catechin content. A normal cup of green tea contains approximately 200mg of EGCG. There is evidence to suggest the catechins in green tea can be used for preventing and treating cancer, cardiovascular diseases, inflammatory diseases, and neurodegenerative diseases. Most of the beneficial effects of green tea are attributed to EGCG. Extracts of green tea, made almost exclusively of EGCG (e.g., Tavigo (R)) are currently marketed and sold for weight management and improving oral and cardiovascular health. The consumption of EGCG has also been associated with various neurological benefits such as reducing symptoms of Parkinson's disease and Alzheimer's disease and in improving cognitive function in general. The beneficial effects of EGCG are often attributed to its potent antioxidant properties, although recent studies have discovered potential neuroprotective properties of the catechin. Currently there are no clinical trials investigating the relationship between EGCG and cognitive function in humans. The premise that EGCG may improve cognitive function is generated from the results of animal studies, and research on antioxidants, flavonoids, and green tea. The following sections of this chapter outline previous research investigating the relationship between antioxidants, flavonoids, green tea, EGCG, and cognitive function. The biological mechanisms by which EGCG may improve cognitive function and suggestions for future research in the area are also discussed.
Advances in natural medicines, nutraceuticals and neurocognition / Con Stough and Andrew Scholey (eds.), Chapter 11, pp. 225-240
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