Phenolic content in tea
The phenolic content in tea refers to the phenols and polyphenols, natural plant compounds which are found in tea. These chemical compounds affect the flavor and mouthfeel and are speculated to provide potential health benefits. Polyphenols in tea include catechins, theaflavins, tannins, and flavonoids.
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.
Catechins constitute about 25% of the dry weight of a fresh tea leaf, 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.
4-Hydroxybenzoic acid, 3,4-dihydroxybenzoic acid (protocatechuic acid), 3-methoxy-4-hydroxy-hippuric acid and 3-methoxy-4-hydroxybenzoic acid (vanillic acid) are the main catechins metabolites found in humans after consumption of green tea infusions.
Catechin monomer structures are metabolized into dimers theaflavins and oligomers thearubigins with increasing degrees of oxidation of tea leaves. Theaflavins directly contribute to the bitterness and astringency of steeped black tea. The mean amount of theaflavins in a cup of black tea (200 ml) is 12.18 mg.
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).
Tannins are astringent, bitter polyphenolic compounds that bind to and precipitate organic compounds. Gallic acid conjugates all of the catechins, such as EGCG (Epigallocatechin gallate), which are tannins with astringent qualities.
A group of natural phenols called the flavonoids are of popular interest because researchers have found them to have the potential to contribute to better health. Tea has one of the highest contents of flavonoids among common food and beverage products. Catechins are the largest type of flavonoids in growing tea leaves. 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.
- Thermo Scientific (Dionex) Application Note 275. Sensitive Determination of Catechins in Tea by HPLC . Retrieved 3 August 2013.
- Balentine DA, Harbowy ME, Graham HN (1998). "Tea: the Plant and its Manufacture; Chemistry and Consumption of the Beverage". In Spiller GA. Caffeine. Boca Raton: CRC Press. ISBN 0-8493-2647-8.[page needed]
- Kanwar, Jyoti; Taskeen, Mujtaba; Mohammad, Imthiyaz; Huo, Congde; Chan, Tak Hang; Dou, Qing Ping (2012). "Recent advances on tea polyphenols". Frontiers in Bioscience 4: 111–31. doi:10.2741/363. PMC 3303150. PMID 22201858.
- Yang, Chung S.; Lambert, Joshua D.; Sang, Shengmin (2008). "Antioxidative and anti-carcinogenic activities of tea polyphenols". Archives of Toxicology 83 (1): 11–21. doi:10.1007/s00204-008-0372-0. PMC 2820244. PMID 19002670.
- Suzuki, Jun-Ichi; Isobe, Mitsuaki; Morishita, Ryuichi; Nagai, Ryozo (2009). "Tea Polyphenols Regulate Key Mediators on Inflammatory Cardiovascular Diseases". Mediators of Inflammation 2009: 1. doi:10.1155/2009/494928. PMC 2712737. PMID 19636434.
- Cabrera, Carmen; Artacho, Reyes; Giménez, Rafael (2006). "Beneficial Effects of Green Tea—A Review". Journal of the American College of Nutrition 25 (2): 79–99. doi:10.1080/07315724.2006.10719518. PMID 16582024.
- 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. PMID 9699018.
- Peterson, 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.
- US Patent 20110064851 A1 (2011) Method of producing fermented tea drink rich in theaflavins. Google Patents. Retrieved 3 August 2013.
- U.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. PMID 15137818.
- Cameron, Amy R.; Anton, Siobhan; Melville, Laura; Houston, Nicola P.; Dayal, Saurabh; McDougall, Gordon J.; Stewart, Derek; Rena, Graham (2008). "Black tea polyphenols mimic insulin/insulin-like growth factor-1 signalling to the longevity factor FOXO1a". Aging Cell 7 (1): 69–77. doi:10.1111/j.1474-9726.2007.00353.x. PMID 18005251.
- Lin, Chih-Li; Huang, Hsiu-Chen; Lin, Jen-Kun (2007). "Theaflavins attenuate hepatic lipid accumulation through activating AMPK in human HepG2 cells". The Journal of Lipid Research 48 (11): 2334–43. doi:10.1194/jlr.M700128-JLR200. PMID 17720960.
- Crozier, Alan; Jaganath, Indu B.; Clifford, Michael N. (2009). "Dietary phenolics: Chemistry, bioavailability and effects on health". Natural Product Reports 26 (8): 1001–43. doi:10.1039/b802662a. PMID 19636448.
- Maki, Kevin C.; Reeves, Matthew S.; Farmer, Mildred; Yasunaga, Koichi; Matsuo, Noboru; Katsuragi, Yoshihisa; Komikado, Masanori; Tokimitsu, Ichiro; Wilder, Donna; Jones, Franz; Blumberg, Jeffrey B.; Cartwright, Yolanda (2008). "Green Tea Catechin Consumption Enhances Exercise-Induced Abdominal Fat Loss in Overweight and Obese Adults". Journal of Nutrition 139 (2): 264–70. doi:10.3945/jn.108.098293. PMID 19074207.