catechin

Epicatechin (EC)

Epigallocatechin (EGC)

Catechins are polyphenolic antioxidant plant metabolites. They belong to the family of flavonoids and, to be more specific, flavan-3-ols. These compounds are abundant in teas derived from the tea-plant Camellia sinensis as well as in some cocoas and chocolates (made from the seeds of Theobroma cacao).

The name of the catechin chemical family derives from catechu which is the juice or boiled extract of Mimosa catechu (Acacia catechu L.f))^[1]

Catechin, epicatechin, gallocatechin, epigallocatechin, and the gallates

Catechin and epicatechin are epimers, with (-)-epicatechin and (+)-catechin being the most common optical isomers found in nature. Catechin was first isolated from the plant extract catechu, avove, from which it derives its name. Heating catechin past its point of decomposition releases pyrocatechol (also called catechol), which explains the common origin of the names of these compounds.

Epigallocatechin and gallocatechin contain an additional phenolic hydroxyl group when compared to epicatechin and catechin, respectively, similar to the difference in pyrogallol compared to pyrocatechol.

Catechin gallates are gallic acid esters of the catechins; such as EGCG (epigallocatechin gallate), which is commonly the most abundant catechin in tea.

Sources of catechins

Catechins constitute about 25% of the dry weight of fresh tea leaf^[2], although total catechin content varies widely depending on clonal variation, growing location, seasonal/ 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.

Catechins are also present in the human diet in chocolate^[3], fruits, vegetables and wine^[4] and are found in many other plant species^[5].

Epigallocatechin gallate is the most abundant catechin in tea.

Another stereoisomer, (-)-catechin, is released from the roots of the invasive weed, spotted knapweed. It acts as an herbicide to inhibit competition by a wide range of other plant species. ^[6]. This phytotoxic compound inhibits seed germination and growth.

Health benefits of catechins

The health benefits of catechins have been studied extensively in humans and in animal models. Reduction in atherosclerotic plaques was seen in animal models.^[7] Reduction in carcinogenesis was seen in vitro.^[8]

Many studies on health benefits have been linked to the catechin content. According to Norman Hollenberg, professor of medicine at Harvard Medical School, epicatechin can reduce the risk of four of the major health problems: stroke, heart failure, cancer and diabetes. He studied the Kuna people in Panama, who drink up to 40 cups of cocoa a week, and found that the prevalence of the “big four” is less than 10%. He believes that epicatechin should be considered essential to the diet and thus classed as a vitamin.^[9][10]

According to one researcher^[11] epigallocatechin-3-gallate is an antioxidant that helps protect the skin from UV radiation-induced damage and tumor formation.

Green tea catechins have also been shown to possess antibiotic properties due to their role in disrupting a specific stage of the bacterial DNA replication process.^[12]

Catechins, when combined with habitual exercise, have been shown to delay some forms of aging. Mice fed catechins showed decreased levels of aging. Oxidative stress was lowered in cell mitochondria, as well as increase in mRNA transcription of mitochondria related proteins. ^[13]

The Lancet medical journal has warned^[14] against increasing one’s intake of dark chocolate in order to improve health, because the beneficial compounds are sometimes removed due to their bitter taste without an indication on the label, and because the fat, sugar, and calories of chocolate increase the risk for heart disease, unless balanced by a reduction of their intake in other foods.

In 2008 UCLA cancer researchers found that study participants who ate foods containing certain flavonoids seemed to be protected from developing lung cancer. Dr. Zuo-Feng Zhang, of the UCLA's Jonsson Cancer Center and a professor of public health and epidemiology at the UCLA School of Public Health said the flavonoids that appeared to be the most protective included catechin, found in strawberries and green and black teas; kaempferol, found in brussel sprouts and apples; and quercetin, found in beans, onions and apples.^[15]

Catechin and epicatechin are also selective monoamine oxidase inhibitors (MAOIs) of type MAO-B.^[16]

See also

• Catechu
• Catechol
• Catecholamines
• Quercetin
• Flavonoid
• Camellia sinensis
• Cocoa
• Tannin
• Polyphenol
• Proanthocyanidin
• Polyphenon
• Phenolic compounds in wine

References

• [3]

External links

• Micronutrient Information Center - Flavonoids
• Tea biochemistry
• Review of a study on green-tea catechins
• Cocoa 'vitamin' health benefits could outshine penicillin
• UK MSN - How cocoa beats killer diseases by Ross Chainey 12/03/07
• (-)Epicatechin mediates beneficial effects of flavonol-rich cocoa on vascular function in humans.