Epigallocatechin gallate

Epigallocatechin gallate (EGCG), also known as epigallocatechin-3-gallate, is the ester of epigallocatechin and gallic acid, and is a type of catechin. EGCG – the most abundant catechin in tea – is a polyphenol under basic research for its potential to affect human health and disease. EGCG is used in many dietary supplements. 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 (936 mg per 100 g). During black tea production, the catechins are mostly converted to theaflavins and thearubigins via polyphenol oxidases. Trace amounts are found in apple skin, plums, onions, hazelnuts, pecans, and carob powder (at 109 mg per 100 g). When taken orally, EGCG has poor absorption even at daily intake equivalent to 8–16 cups of green tea, an amount causing adverse effects such as nausea or heartburn. After consumption, EGCG blood levels peak within 1.7 hours. The absorbed plasma half-life is ~5 hours, but with majority of unchanged EGCG excreted into urine 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. Well-studied in basic research, EGCG has various biological effects in laboratory studies. A 2011 analysis by the European Food Safety Authority 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. A 2018 review showed that excessive intake of EGCG may cause liver toxicity. In 2018, the European Food Safety Authority 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.