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 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.
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.
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).
According to a report released by USDA, in a 200-ml cup of tea, the mean total content of flavonoids is 233.12 mg for black tea.
Tannins are astringent, bitter polyphenolic compounds that bind to and precipitate organic compounds. Gallic acid conjugates of the catechins, such as EGCG (Epigallocatechin gallate), 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.
- 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.
- U.S. Department of Agriculture, USDA Database for the Flavonoid Content of Selected Foods, Release 2.1, January 2007
- Kanwar J, et al (2012) Recent advances on tea polyphenols. Front Biosci (Elite Ed). 1;4:111-31.
- Yang CS et al, (2009) Antioxidative and anti-carcinogenic activities of tea polyphenols Archives of Toxicology 83(1): 11-25
- Jun-ichi Suzuki et al, Tea Polyphenols Regulate Key Mediators on Inflammatory Cardiovascular Diseases, Mediators of Inflammation Volume 2009, Article ID 494928
- Carmen Cabrera et al, Beneficial Effects of Green Tea—A Review, Journal of the American College of Nutrition, 25(2): 79–99, 2006
- Catechin metabolites after intake of green tea infusions. P. G. Pietta, P. Simonetti, C. Gardana, A. Brusamolino, P. Morazzoni and E. Bombardelli, BioFactors, 1998, Volume 8, Issue 1-2, pp. 111–118,doi:10.1002/biof.5520080119
- Peterson J et al (2005) Major flavonoids in dry tea Journal of Food Composition and Analysis 18: 487–501, 2005
- US Patent 20110064851 A1 (2011) Method of producing fermented tea drink rich in theaflavins. Google Patents. Retrieved 3 August 2013.
- Del Rio D, Stewart AJ, Mullen W, Burns J, Lean ME, Brighenti F, Crozier A. (2004). "HPLC-MSn Analysis of Phenolic Compounds and Purine Alkaloids in Green and Black Tea". J Agric Food Chem.19;52(10):2807-15. PMID 15137818
- Cameron AR, et al (2008) Black tea polyphenols mimic insulin/insulin-like growth factor-1 signaling to the longevity factor FOXO1a Aging Cell 7(1):69-77
- Chih-Li Lin et al, Theaflavins attenuate hepatic lipid accumulation through activating AMPK in human HepG2 cells, Journal of Lipid Research 48: 2334~2340, 2007
- Crozier A, et al (2009) Dietary phenolics: chemistry, bioavailability and effects on health. Nat Prod Rep 26(8):1001-43
- Maki KC et al (2009) Green Tea Catechin Consumption Enhances Exercise-Induced Abdominal Fat Loss in Overweight and Obese Adults Journal of Nutrition 139: 264–270