Epigallocatechin Gallate (EGCG)
Green tea is the second-most consumed beverage in the world (water is the first) and has been used medicinally for centuries in India and China. A number of beneficial health effects are attributed to regular consumption of green tea and dried/powdered extracts of green tea are available as dietary supplements
The active constituents in green tea are a family of polyphenols (catechins) and flavonols which possess potent antioxidant activity. Tannins, large polyphenol molecules, form the bulk of the active compounds in green tea, with catechins comprising nearly 90%. Several catechins are present in significant quantities; epicatechin (EC), epigallocatechin (EGC), epicatechin gallate (ECG) and epigallocatechin gallate (EGCG). EGCG makes up about 10-50% of the total catechin content and appears to be the most powerful of the catechins – with antioxidant activity about 25-100 times more potent than vitamins C and E. A cup of green tea may provide 10-40mg of polyphenols and has antioxidant activity greater than a serving of broccoli, spinach, carrots or strawberries. A number of commercial green tea extracts are standardized to total polyphenol content and/or EGCG content.
Epigallocatechin gallate (EGCG) is one of four major catechins in green tea. Catechins belong to the flavan-3-ol class of flavonoids. Green tea catechins are the flavan-3-ols found in green tea leaves. All catechins including EGCG are polyphenolic substances. Black tea leaves have a much lower content of these catechins. That's because black tea leaves undergo extensive fermentation, during which the majority of the catechins are enzymatically oxidized to the major pigments of black tea leaves, theaflavin and thearubigen.
Because the active compounds, the catechins, found in green tea are known to possess potent antioxidant activity, they may provide beneficial health effects by protecting the body from the damaging effects of oxidative damage from free radicals. A number of chronic disease states have been associated with free radical induced oxidative damage, including cancer, heart disease, suppressed immune function and accelerated aging. EGCG is beneficial to individuals at high risk for cancer (e.g. family history) or those undergoing chemotherapy or radiation treatment. Also beneficial as a general protective measure and dietary "insurance" of adequate polyphenol intake. Recent data provides strong evidence that green tea may be effective in stimulating thermogenesis, increasing caloric expenditure, promoting fat oxidation and controlling body weight.