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" redirects here. For the software, see Extended GCG.
Epigallocatechin gallate
Names
IUPAC name
[(2R,3R)-5,7-dihydroxy-2-(3,4,5-trihydroxyphenyl)chroman-3-yl] 3,4,5-trihydroxybenzoate
Preferred IUPAC name
(2R,3R)-5,7-dihydroxy-2-(3,4,5-trihydroxyphenyl)-3,4-dihydro-2H-1-benzopyran-3-yl 3,4,5-trihydroxybenzoate
Other names
(-)-Epigallocatechin gallate
(2R,3R)-3′,4′,5,5′,7-pentahydroxyflavan-3-yl gallate
Identifiers
3D model (JSmol)
ChEBI
ChEMBL
ChemSpider
ECHA InfoCard 100.111.017
MeSH Epigallocatechin+gallate
UNII
Properties
C22H18O11
Molar mass 458.372 g/mol
soluble (33.3-100 g/L)[1]
Solubility soluble in ethanol, DMSO, dimethyl formamide[1] at about 20 g/l[2]
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

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.

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 (936 mg per 100 g).[3] During black tea production, the catechins are mostly converted to theaflavins and thearubigins via polyphenol oxidases.[4]

Other

Trace amounts are found in apple skin, plums, onions, hazelnuts, pecans, and carob powder (at 109 mg per 100 g).[3]

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 such as nausea or heartburn.[5] After consumption, EGCG blood levels peak within 1.7 hours.[6] The absorbed plasma half-life is ~5 hours,[6] but with majority of unchanged EGCG excreted into urine over 0 to 8 hours.[6] Methylated metabolites appear to have longer half-lives and occur at 8-25 times the plasma levels of unmetabolized EGCG.[7]

Research

Well-studied in basic research, EGCG has various biological effects in laboratory studies.[8][9][10][11] EGCG is a modulator of the GABAA receptor.[12]

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.[13] 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.[14]

Potential toxicity

A 2018 review showed that excessive intake of EGCG may cause liver toxicity.[15] In 2018, the European Food Safety Authority stated that daily intake of 800 mg or more could increase risk of liver damage.[16] The degree of toxicity varies by person, suggesting that it is potentiated by genetic predisposition and the diet eaten during the period of ingestion, or other factors.[17]

Rat studies have shown that EGCG concentrations in the liver are about four times greater than in blood plasma.[18] Toxic effects can be seen in the liver without any toxic effects in other organs or tissues.[18] Antioxidants may reduce the toxic effects of EGCG.[18]

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.[19] 100 mL of green tea contains about 70.2 mg of EGCG.[20] (about 165 mg per cup).

Regulation

Over 2008 to 2017, the US Food and Drug Administration 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 the treatment or prevention of diseases or conditions that cause them to be classified as drugs under the United States code,[21][22][23] while another focused on inadequate quality assurance procedures and labeling violations.[24] 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.[23]

See also

References
  1. "(-)-Epigallocatechin gallate". Chemicalland21.com.
  2. "Product Information: (-)-Epigallocatechin Gallate" (PDF). Cayman Chemical. 4 September 2014.
  3. Bhagwat, Seema; Haytowitz, David B.; Holden, Joanne M. (September 2011). USDA Database for the Flavonoid Content of Selected Foods, Release 3 (PDF) (Report). Agricultural Research Service, U.S. Department of Agriculture. pp. 2, 98–103. Retrieved 18 May 2015.
  4. Lorenz, Mario; Urban, Janka; Engelhardt, Ulrich; Baumann, Gert; Stangl, Karl; Stangl, Verena (January 2009). "Green and Black Tea are Equally Potent Stimuli of NO Production and Vasodilation: New Insights into Tea Ingredients Involved". Basic Research in Cardiology. 104 (1): 100–110. doi:10.1007/s00395-008-0759-3. PMID 19101751.
  5. Chow, H-H. Sherry; Cai, Yan; Hakim, Iman A.; Crowell, James A.; Shahi, Farah; Brooks, Chris A.; Dorr, Robert T.; Hara, Yukihiko; Alberts, David S. (15 August 2003). "Pharmacokinetics and safety of green tea polyphenols after multiple-dose administration of epigallocatechin gallate and polyphenon E in healthy individuals". Clinical Cancer Research. 9 (9): 3312–3319. PMID 12960117.
  6. Lee, Mao-Jung; Maliakal, Pius; Chen, Laishun; Meng, Xiaofeng; Bondoc, Flordeliza Y.; Prabhu, Saileta; Lambert, George; Mohr, Sandra; Yang, Chung S. (October 2002). "Pharmacokinetics of tea catechins after ingestion of green tea and (-)-epigallocatechin-3-gallate by humans: formation of different metabolites and individual variability". Cancer Epidemiology, Biomarkers & Prevention. 11 (10 Pt 1): 1025–1032. PMID 12376503.
  7. Manach, C; Williamson, G; Morand, C; Scalbert, A; Rémésy, C (January 2005). "Bioavailability and bioefficacy of polyphenols in humans. I. Review of 97 bioavailability studies". The American Journal of Clinical Nutrition. 81 (1 Suppl): 230S–242S. doi:10.1093/ajcn/81.1.230S. PMID 15640486.
  8. Fürst, Robert; Zündorf, Ilse (May 2014). "Plant-derived anti-inflammatory compounds: hopes and disappointments regarding the translation of preclinical knowledge into clinical progress". Mediators of Inflammation. 2014: 1–9. doi:10.1155/2014/146832. PMC 4060065. PMID 24987194. 146832.
  9. Granja, Andreia; Frias, Iúri; Neves, Ana Rute; Pinheiro, Marina; Reis, Salette (2017). "Therapeutic Potential of Epigallocatechin Gallate Nanodelivery Systems". BioMed Research International. 2017: 1–15. doi:10.1155/2017/5813793. ISSN 2314-6133. PMC 5534279. PMID 28791306.
  10. Wu, Dayong; Wang, Junpeng; Pae, Munkyong; Meydani, Simin Nikbin (2012). "Green tea EGCG, T cells, and T cell-mediated autoimmune diseases". Molecular Aspects of Medicine. 33 (1): 107–118. doi:10.1016/j.mam.2011.10.001. ISSN 0098-2997. PMID 22020144.
  11. Riegsecker, Sharayah; Wiczynski, Dustin; Kaplan, Mariana J.; Ahmed, Salahuddin (2013). "Potential benefits of green tea polyphenol EGCG in the prevention and treatment of vascular inflammation in rheumatoid arthritis". Life Sciences. 93 (8): 307–312. doi:10.1016/j.lfs.2013.07.006. PMC 3768132. PMID 23871988.
  12. Hanrahan, Jane R.; Chebib, Mary; Johnston, Graham A. R. (18 April 2011). "Flavonoid modulation of GABAA receptors". British Journal of Pharmacology. 163 (2): 234–245. doi:10.1111/j.1476-5381.2011.01228.x. ISSN 0007-1188. PMC 3087128. PMID 21244373.
  13. EFSA NDA Panel (EFSA Panel on Dietetic Products, Nutrition and Allergies) (2011). "Scientific Opinion on the substantiation of health claims related to Camellia sinensis (L.) Kuntze (tea), including catechins in green tea, and improvement of endothelium-dependent vasodilation (ID 1106, 1310), maintenance of normal blood pressure". EFSA Journal. 9 (4): 2055. doi:10.2903/j.efsa.2011.2055.
  14. Momose Y; et al. (2016). "Systematic review of green tea epigallocatechin gallate in reducing low-density lipoprotein cholesterol levels of humans". Int J Food Sci Nutr. 67 (6): 606–13. doi:10.1080/09637486.2016.1196655. PMID 27324590.
  15. Hu, J; Webster, D; Cao, J; Shao, A (2018). "The safety of green tea and green tea extracts consumption in adults - Results of a systematic review". Regulatory Toxicology and Pharmacology. 95: 412–433. doi:10.1016/j.yrtph.2018.03.019. PMID 29580974.
  16. Younes, Maged; Aggett, Peter; Aguilar, Fernando; Crebelli, Riccardo; Dusemund, Birgit; Filipič, Metka; Frutos, Maria Jose; Galtier, Pierre; Gott, David; Gundert‐Remy, Ursula; Lambré, Claude; Leblanc, Jean‐Charles; Lillegaard, Inger Therese; Moldeus, Peter; Mortensen, Alicja; Oskarsson, Agneta; Stankovic, Ivan; Waalkens‐Berendsen, Ine; Woutersen, Rudolf Antonius; Andrade, Raul J.; Fortes, Cristina; Mosesso, Pasquale; Restani, Patrizia; Arcella, Davide; Pizzo, Fabiola; Smeraldi, Camilla; Wright, Matthew (18 April 2018). "Scientific opinion on the safety of green tea catechins". EFSA Journal. 16 (4). doi:10.2903/j.efsa.2018.5239.
  17. Quinn, Tristan (2018-10-25), "The food supplement that ruined my liver [Tristan Quinn's article about Jim McCants]", BBC News, retrieved 2018-10-27.
  18. Ouyang J, Zhu K, Liu Z, Huang J (2020). "Prooxidant Effects of Epigallocatechin-3-Gallate in Health Benefits and Potential Adverse Effect". Oxidative Medicine and Cellular Longevity. 2020: 9723686. doi:10.1155/2020/9723686. PMC 7441425. PMID 32850004.
  19. Hu J, Webster D, Cao J, Shao A (2018). "The safety of green tea and green tea extract consumption in adults - Results of a systematic review". Regulatory Toxicology and Pharmacology. 95: 412–433. doi:10.1016/j.yrtph.2018.03.019. PMID 29580974.
  20. Younes M, Aggett P, Aguilar F, Wright M (2018). "Scientific opinion on the safety of green tea catechins". EFSA Journal. 16 (4): e05239. doi:10.2903/j.efsa.2018.5239. PMC 7009618. PMID 32625874.
  21. "Sharp Labs Inc: Warning Letter". Inspections, Compliance, Enforcement, and Criminal Investigations. Food and Drug Administration. 9 July 2008. Archived from the original on 23 October 2016. Retrieved 15 September 2015.
  22. "Fleminger Inc.: Warning Letter". Inspections, Compliance, Enforcement, and Criminal Investigations. Food and Drug Administration. 22 February 2010. Archived from the original on 23 October 2016. Retrieved 6 January 2015.
  23. "LifeVantage Corporation: Warning Letter". Inspections, Compliance, Enforcement, and Criminal Investigations. Food and Drug Administration. 17 April 2017. Retrieved 30 September 2017.
  24. "N.V.E. Pharmaceuticals, Inc.: Warning Letter". Inspections, Compliance, Enforcement, and Criminal Investigations. Food and Drug Administration. 22 July 2013. Retrieved 30 September 2017.
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