Catechin

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Catechins are plant metabolites belonging to the flavonoid family. They are considered powerful anti-oxidants. The best source of catechins is white tea, with green tea coming close. Catechins are linked to evidence of fighting tumors as well as enhancing immune system function, due to their polyphenol antioxidant character, which is well established in scavenging reactive oxygen species.

1 Sources of catechins
2 Catechins and health
- 2.1 Catechins as MAO-B inhibitors
- 2.2 Catechins as antioxidants
3 Notes
4 References
5 External links

[edit] Sources of catechins

Catechins make up some 10% of the dry weight of fresh tea leaf[2]. The concentration of catechins is higher in green and white tea. In black tea the oxidation process allows polyphenol oxidase to oxidize the polyphenols[2] and so inactivates the catechins.

Tea contains four main catechin substances: epicatechin (EC), epicatechin gallate (ECg), epigallocatechin (EGC) and epigallocatechin gallate (EGCg). Catechin gallates are esters of a catechin and gallic acid whereas gallocatechins have the same carbon skeleton as other catechins but have an extra hydroxyl group. Epigallocatechin gallate (EGCG) is the one most abundant catechins in tea. EGCG as an antioxidant is about 25-100 times more potent than vitamins C and E.^{[citation needed]}

Tea flavour, colour and astringency is in part due to the condensation of the catechins to form the bright orange-red pigment theaflavin.[2]

Catechines are also found in chocolate.

[edit] Catechins and health

[edit] Catechins as MAO-B inhibitors

Recently, (+)-catechin and (−)-epicatechin, isolated from Uncaria species (Cat's Claw) were demonstrated to have monoamine oxidase-B inhibitory properties, with Ki values of 74 and 21 µM, respectively. <ref>J Ethnopharmacology 2005 Aug 22;100(1-):216-20 Hou WC, et al.</ref> Inhibition of MAO-B may protect against oxidative neurological damage; in fact several Parkinson's and Alzheimer's drugs are believed to work as MAO-B inhibitors, such as selegeline, or l-deprenyl.

[edit] Catechins as antioxidants

One cup of green tea provides 10-40 mg of polyphenols and has antioxidant effects greater than a serving of broccoli, spinach, carrots, or strawberries. ^{[citation needed]} The high antioxidant activity of green tea makes it beneficial for protecting the body from oxidative damage due to free radicals. Research shows that green tea may help the arterial wall by reducing oxidized lipids<ref>Serafini M, Laranjinha JA, Almeida LM, Maiani G, Inhibition of human LDL lipid peroxidation by phenol-rich beverages and their impact on plasma total antioxidant capacity in humans, J Nutr Biochem 2000 Nov;11(11-12):585-590</ref>. Green tea can protect against experimentally induced DNA damage, and slow or halt the initiation and progression of undesirable cell colonies^{[citation needed]}. Studies show evidence that green tea provides immunoprotective qualities^{[citation needed]}, particularly in the case of patients undergoing radiation or chemotherapy^{[citation needed]}. White blood cell count appear to be maintained more effectively in patients consuming green tea compared to non-supplemented patients.^{[citation needed]}

A 2006 study showed that elderly Japanese people who drank more than 2 cups of green tea a day had a 50 per cent lower chance of cognitive impairment than those who drank less green tea, or who consumed other tested beverages. The high amount of catechins in green tea was believed to be responsible. White tea, (which is higher in catechins than green tea), was not tested. The study was published in "The American Journal of Clinical Nutrition" (Vol. 83, pp. 355-361)^[1]

Researchers believe that catechin is effective because it easily sticks to proteins, blocking bacteria from adhering to cell walls and disrupting their ability to destroy them. Viruses have ‘hooks’ on their surfaces and can attach to cell walls^{[citation needed]}. The catechin in green tea prevents viruses from adhering and causing harm^{[citation needed]}. Catechin reacts with toxins created by harmful bacteria (many of which belong to the protein family) and harmful metals such as lead, mercury, chrome, and cadmium.^{[citation needed]}

[edit] Notes

[edit] References

Linus Pauling Institute (Oregon State University) Micronutrient Information Center - Flavonoids
Science and Plants for Schools Website http://www-saps.plantsci.cam.ac.uk/records/rec281.htm
↑ Green tea consumption and cognitive function: a cross-sectional study from the Tsurugaya Project 1. Kuriyama, et. al. Am J Clin Nutr. 2006 Feb;83(2):355-61. Pubmed