Phenolic content in tea

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Most of the polyphenols in green tea are flavan-3-ols (catechins).

Phenols and polyphenols are compounds found naturally in plants. 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.[1][2][3][4][5]

Tea has one of the highest contents of flavonoids among common food and beverage products.[6] Catechins are the largest type of flavonoids in growing tea leaves.[7]

Contents

Catechins [edit]

Catechins in tea include epigallocatechin-3-gallate (EGCG), epicatechin (EC), epicatechin-3-gallate (ECg), epigallocatechin (EGC), catechin, and gallocatechin (GC).[citation needed]

Catechins constitute about 25% of the dry weight of fresh tea leaf,[8] 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.[6]

Of all the catechins in tea, EGCG is the main subject of scientific study with regard to its potential health effects.[1][2][4][5]

Theaflavins [edit]

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.[7]. Theaflavins directly contribute to the bitterness and astringency of steeped black tea.[citation needed] The mean amount of theaflavins in a cup of black tea (200 ml) is 12.18 mg.[6]

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).[citation needed]

A number of laboratory studies on their possible health effects have been conducted.[9][10]

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.[6]

Tannins [edit]

Tannins, which are astringent, bitter polyphenolic compounds, are found in tea.[11]

Metabolism [edit]

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.[12]

See also [edit]

References [edit]

  1. ^ a b Kanwar J, et al (2012) Recent advances on tea polyphenols. Front Biosci (Elite Ed). 1;4:111-31.
  2. ^ a b Yang CS et al, (2009) Antioxidative and anti-carcinogenic activities of tea polyphenols Archives of Toxicology 83(1): 11-25
  3. ^ 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
  4. ^ a b Suzuki JI et al (2009) Tea Polyphenols Regulate Key Mediators on Inflammatory Cardiovascular Diseases Mediators of Inflammation 2009:494928.
  5. ^ a b Cabrera C et al (2006) Beneficial Effects of Green Tea—A Review. J Am Coll Nutr. 2006 Apr;25(2):79-99.
  6. ^ a b c d U.S. Department of Agriculture, USDA Database for the Flavonoid Content of Selected Foods, Release 2.1, January 2007
  7. ^ a b Peterson J et al (2005) Major flavonoids in dry tea Journal of Food Composition and Analysis 18: 487–501, 2005
  8. ^ 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. 
  9. ^ 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
  10. ^ 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
  11. ^ Crozier A, et al (2009) Dietary phenolics: chemistry, bioavailability and effects on health. Nat Prod Rep 26(8):1001-43
  12. ^ 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
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