Epigallocatechin gallate (EGCG), also known as epigallocatechin-3-gallate, is the

ester In chemistry, an ester is a compound derived from an oxoacid (organic or inorganic) in which at least one hydroxyl group () is replaced by an alkoxy group (), as in the substitution reaction of a carboxylic acid and an alcohol. Glycerides a ...

epigallocatechin Gallocatechol or gallocatechin (GC) is a flavan-3-ol, a type of chemical compound including catechin, with the gallate residue being in an isomeric trans position. This compound possesses two epimers. The most common, (+)-gallocatechin (GC), CAS ...

and

gallic acid Gallic acid (also known as 3,4,5-trihydroxybenzoic acid) is a trihydroxybenzoic acid with the formula C6 H2( OH)3CO2H. It is classified as a phenolic acid. It is found in gallnuts, sumac, witch hazel, tea leaves, oak bark, and other plants. I ...

, and is a type of

catechin Catechin is a flavan-3-ol, a type of secondary metabolite providing antioxidant roles in plants. It belongs to the subgroup of polyphenols called flavonoids. The name of the catechin chemical family derives from ''catechu'', which is the tanni ...

. EGCG – the most abundant catechin in

tea Tea is an aromatic beverage prepared by pouring hot or boiling water over cured or fresh leaves of ''Camellia sinensis'', an evergreen shrub native to East Asia which probably originated in the borderlands of southwestern China and north ...

– is a

polyphenol Polyphenols () are a large family of naturally occurring organic compounds characterized by multiples of phenol units. They are abundant in plants and structurally diverse. Polyphenols include flavonoids, tannic acid, and ellagitannin, some o ...

under

basic research Basic research, also called pure research or fundamental research, is a type of scientific research with the aim of improving scientific theories for better understanding and prediction of natural or other phenomena. In contrast, applied rese ...

for its potential to affect human health and disease. EGCG is used in many dietary supplements.

Food sources

Tea

It is found in high content in the dried leaves of green tea (7380 mg per 100 g), white tea (4245 mg per 100 g), and in smaller quantities,

black tea Black tea, also translated to red tea in various East Asian languages, is a type of tea that is more oxidized than oolong, yellow, white and green teas. Black tea is generally stronger in flavour than other teas. All five types are made from ...

(936 mg per 100 g). During black tea production, the catechins are mostly converted to

theaflavin Theaflavin (TF) and its derivatives, known collectively as ''theaflavins'', are antioxidant polyphenols that are formed from the condensation of flavan-3-ols in tea leaves during the enzymatic oxidation (sometimes erroneously referred to as fermen ...

s and

thearubigin Thearubigins are polymeric polyphenols that are formed during the enzymatic oxidation and condensation of two gallocatechins (epigallocatechin and epigallocatechin gallate) with the participation of polyphenol oxidases during the fermentation rea ...

s via

polyphenol oxidase Polyphenol oxidase (PPO; also polyphenol oxidase i, chloroplastic), an enzyme involved in fruit browning, is a tetramer that contains four atoms of copper per molecule. PPO may accept monophenols and/or ''o''-diphenols as substrates. The ...

Other

Trace amounts are found in

apple An apple is an edible fruit produced by an apple tree (''Malus domestica''). Apple trees are cultivated worldwide and are the most widely grown species in the genus ''Malus''. The tree originated in Central Asia, where its wild ancestor, ' ...

skin, plums,

onion An onion (''Allium cepa'' L., from Latin ''cepa'' meaning "onion"), also known as the bulb onion or common onion, is a vegetable that is the most widely cultivated species of the genus ''Allium''. The shallot is a botanical variety of the onio ...

s, hazelnuts,

pecans The pecan (''Carya illinoinensis'') is a species of hickory native to the southern United States and northern Mexico in the region of the Mississippi River. The tree is cultivated for its seed in the southern United States, primarily in Georgia, ...

, and carob powder (at 109 mg per 100 g).

Bioavailability

When taken orally, EGCG has poor absorption even at daily intake equivalent to 8–16 cups of green tea, an amount causing

adverse effects An adverse effect is an undesired harmful effect resulting from a medication or other intervention, such as surgery. An adverse effect may be termed a "side effect", when judged to be secondary to a main or therapeutic effect. The term complica ...

such as

nausea Nausea is a diffuse sensation of unease and discomfort, sometimes perceived as an urge to vomit. While not painful, it can be a debilitating symptom if prolonged and has been described as placing discomfort on the chest, abdomen, or back of the ...

heartburn Heartburn, also known as pyrosis, cardialgia or acid indigestion, is a burning sensation in the central chest or upper central abdomen. Heartburn is usually due to regurgitation of gastric acid (gastric reflux) into the esophagus. It is the m ...

. After consumption, EGCG blood levels peak within 1.7 hours. The absorbed

plasma half-life Biological half-life (also known as elimination half-life, pharmacologic half-life) is the time taken for concentration of a biological substance (such as a medication) to decrease from its maximum concentration ( Cmax) to half of Cmax in the bl ...

is ~5 hours, but with majority of unchanged EGCG excreted into

urine Urine is a liquid by-product of metabolism in humans and in many other animals. Urine flows from the kidneys through the ureters to the urinary bladder. Urination results in urine being excreted from the body through the urethra. Cellular ...

over 0 to 8 hours. Methylated metabolites appear to have longer half-lives and occur at 8–25 times the plasma levels of unmetabolized EGCG.

Research

Well-studied in

, EGCG has various biological effects in laboratory studies. A 2011 analysis by the

European Food Safety Authority The European Food Safety Authority (EFSA) is the agency of the European Union (EU) that provides independent scientific advice and communicates on existing and emerging risks associated with the food chain. EFSA was established in February 2002, ...

found that a cause and effect relationship could not be shown for a link between tea catechins and the maintenance of normal blood LDL-cholesterol concentration. A 2016 review found that high daily doses (107 to 856 mg/day) taken by human subjects over four to 14 weeks produced a small reduction of

LDL cholesterol Low-density lipoprotein (LDL) is one of the five major groups of lipoprotein that transport all fat molecules around the body in extracellular water. These groups, from least dense to most dense, are chylomicrons (aka ULDL by the overall dens ...

Potential toxicity

A 2018 review showed that excessive intake of EGCG may cause liver toxicity. In 2018, the

stated that daily intake of 800 mg or more could increase risk of liver damage. Taken as a capsule or tablet 338 mg per day of EGCG is considered safe, whereas 704 mg per day is safe if consumed as a tea beverage. 100 mL of green tea contains about 70.2 mg of EGCG (about 165 mg per cup).

Regulation

Over 2008 to 2017, the US

Food and Drug Administration The United States Food and Drug Administration (FDA or US FDA) is a List of United States federal agencies, federal agency of the United States Department of Health and Human Services, Department of Health and Human Services. The FDA is respon ...

issued several warning letters to manufacturers of dietary supplements containing EGCG for violations of the Federal Food, Drug, and Cosmetic Act. Most of these letters informed the companies that their promotional materials promoted EGCG-based dietary supplements in the treatment or prevention of diseases or conditions that cause them to be classified as drugs under the United States code, while another focused on inadequate quality assurance procedures and labeling violations. The warnings were issued because the products had not been established as safe and effective for their marketed uses and were promoted as " new drugs", without approval as required under the Act.

References

{{Teas 11β-Hydroxysteroid dehydrogenase inhibitors Aromatase inhibitors Flavanols