What is EGCG?
By JP Saleeby, MD
What is EGCG? What was once an esoteric chemical compound know only to a few scientist is now plastered on everything from tea labels to bottle of supplements at the health food store to cover articles in health and medical journals. Google it and you come up with over 600,000 hits. So what exactly is this substance and why is it all the rage these days?
EGCG is the acronym for Epigallocatechin Gallate. It is one of four major polyphenolic substances called catechins found in green tea. A catechin is a substance belonging to the flavan-3-ol class of flavonoids. Catechins are found in higher concentrations in green tea than in black tea for the simple reason that during the oxidation process (where green tea becomes black tea) some of these catechins are converted enzymatically to compounds that give black tea its color namely theaflavin and thearubigen. Unfortunately theaflavin and thearubigen don’t share the same potent health benefits of EGCG.
The catechins found in green tea are responsible for many of the claimed health benefits of the plant. They are antioxidants, with researchers claiming that EGCG the most powerful antioxidant of them all in that class of substances.
Tea contains the four catechins: catechin (EC), epicatechin gallate (ECg), epigallocatechin (EGC) and EGCG (or EGCg). EGCG is of course the most abundant of the four and makes up some 10% of the dry weight of fresh tealeaves. It so happens that EGCG is an antioxidant with about 25 to 100 times (depending on whose research you believe) the potency of Vitamins C & E.
Epigallocatechin gallate may provide certain health benefits by protecting our cells from free-radical oxidative damage. Cancer, arteriosclerosis, heart diseases and accelerated aging are just a number of diseases that have been associated with oxidative damage. EGCG apparently interferes with certain enzyme systems to exact its effect. It inhibits fast-binding and reversible fatty acid synthase, increases tyrosine phosphorylation of the insulin receptor, and activation of ornithine decarboxylase. These enzymatic pathways are important chemical reactions that occur in our bodies that are related to disease and health. EGCG has been shown in research protect our DNA from ultraviolet and radiation-induced damage. Some have reported that this substance may be effective in promoting weight loss by a fat oxidation process.
Additionally, researchers have found that catechins block bacteria and viruses from attaching to human cell walls. Catechins also react with toxins released from harmful bacteria and make them inactive or less active. They also seem to reduce the toxic effects of such heavy metals as cadmium, chrome, lead and mercury.
So how does EGCG form in tealeaves? The process begins with a product of glycolysis (the breakdown of sugar by an enzyme named enolase): phosphoenolpyruvate (PEP). PEP then enters into the Shikimate enzymatic pathway to yield phenylalanine. Interestingly enough in the pharmaceutical industry this pathway is used to produce shikimic acid from the “star anise” plant that is used as a substrate in the production of the popular anti-flu drug oseltamivir (Tamiflu).
From Phenylalanine the process continues through the phenylpropanoid metabolic pathway from which 4-Coumaryl-CoQ is produced. When this compound combines with Malonyl-CoA it yields the true backbone of the flavonoid group known as the chalcones. Three-ring phenolic structures (what is commonly recognized and hence given the name poly-phenol) are produced when ring-closure occurs within these chalcone molecules. The metabolic pathway continues through a series of several more enzymatic modifications to yield flavanones that yield dihydroflavonols that go on to produce anthocyanins. Along this enzymatic highway other products are formed, including the flavonols, flavan-3-ols, proanthocyanidins (the tannins) and of course the all-important polyphenolic EGCG.
JP Saleeby, MD is medical director of the emergency department at MPH in Bennettsville, SC. He practices preventive integrative medicine throughout the southeastern United States and is the medical & health writer for the Tea Experience Digest magazine, a national quarterly tea industry journal.