Catechins include epigallocatechin-3-gallate (EGCG), epicatechin (EC), epicatechin-3-gallate (ECg), epigallocatechin (EGC), catechin, and gallocatechin (GC). The content of EGCG is higher in green tea.[2]
Catechins constitute about 25% of the dry mass of a fresh tea leaf,[3] although total catechin content varies widely depending on species, clonal variation, growing location, season, light variation, and altitude. They are present in nearly all teas made from Camellia sinensis, including white tea, green tea, black tea and oolong tea.
Darjeeling black tea infusion: Finer black tea has a more orange tone than red as a result of higher theaflavins content.
Catechin monomer structures are metabolized into dimers theaflavins and oligomers thearubigins with increasing degrees of oxidation of tea leaves.[6] Theaflavins contribute to the bitterness and astringency of black tea. The mean amount of theaflavins in a cup of black tea (200 ml) is 12.18 mg.[7]
Three main types of theaflavins are found in black tea, namely theaflavin (TF-1), theaflavin-3-gallate (TF-2), and theaflavin-3,3-digallate (TF-3).[8]
Phenols called flavonoids are under preliminary research, as of 2020, but there is no evidence that flavonoids have antioxidant activity in vivo, or affect physical health or diseases.[10][11] Tea has one of the highest contents of flavonoids among common food and beverage products.[7]Catechins are the largest type of flavonoids in growing tea leaves.[6] According to a report released by USDA, in a 200-ml cup of tea, the mean total content of flavonoids is 266.68 mg for green tea, and 233.12 mg for black tea.[7]
^Balentine DA, Harbowy ME, Graham HN (1998). "Tea: the Plant and its Manufacture; Chemistry and Consumption of the Beverage". In Spiller GA (ed.). Caffeine. Boca Raton: CRC Press. p. 35. ISBN978-0-8493-2647-9.
^Pietta, P. G.; Simonetti, P.; Gardana, C.; Brusamolino, A.; Morazzoni, P.; Bombardelli, E. (1998). "Catechin metabolites after intake of green tea infusions". BioFactors. 8 (1–2): 111–8. doi:10.1002/biof.5520080119. PMID9699018. S2CID37684286.
^ abPeterson, J.; Dwyer, J.; Bhagwat, S.; Haytowitz, D.; Holden, J.; Eldridge, A.L.; Beecher, G.; Aladesanmi, J. (2005). "Major flavonoids in dry tea". Journal of Food Composition and Analysis. 18 (6): 487–501. doi:10.1016/j.jfca.2004.05.006. hdl:10113/7266.
^ abcU.S. Department of Agriculture, USDA Database for the Flavonoid Content of Selected Foods, Release 2.1, January 2007[non-primary source needed]
^Del Rio, Daniele; Stewart, Amanda J.; Mullen, William; Burns, Jennifer; Lean, Michael E. J.; Brighenti, Furio; Crozier, Alan (2004). "HPLC-MSnAnalysis of Phenolic Compounds and Purine Alkaloids in Green and Black Tea". Journal of Agricultural and Food Chemistry. 52 (10): 2807–15. doi:10.1021/jf0354848. PMID15137818.
^Crozier, Alan; Jaganath, Indu B.; Clifford, Michael N. (2009). "Dietary phenolics: Chemistry, bioavailability and effects on health". Natural Product Reports. 26 (8): 1001–43. CiteSeerX10.1.1.608.4407. doi:10.1039/b802662a. PMID19636448.
^"Flavonoids". Linus Pauling Institute, Oregon State University, Corvallis. 2016. Retrieved 2020-04-15.
