biosynthesis of catechins in tea

Tea is a widely consumed beverage in the world after the second water, health benefits for too many have been found. The tea plant, Camellia sinensis is a family of theaceae. And black tea, and green tea is produced from leaves. The hallmark of this plant is a shrub or a tree is green, and the plant has a height up to 30 feet, but usually trimmed to 2-5 feet for processing. The leaves are dark green oval with serrated rim, scented white flowers, growing in clusters or single.

Unlike black tea, green tea production does not require oxidation of the tea leaves are young. Green tea is produced from boiling fresh tea leaves at high temperatures, causing the enzyme inactive pengoksidasinya so its polyphenol content will still be there. Polyphenols are commonly found in plants known as flavanols or catechins. The main component of catechins found in green tea are: epigallocatechin (EGC), epicatechin (EC), epigallocatechingallate (EGCG) and epicatechin gallate (ECG). Polyphenols from green tea showed antioxidant effects, antikarsinolgenik, anti-inflammatory, thermogenic, probiotic and antikmikroba in some animals and in vitro studies.
Mechanism of Action:
Anticarcinogenic effects of green tea polyphenols mainly of EGCG. EGCG can inhibit tumor initiation and promotion, unduksi apoptosis and inhibit cell replication rate pertembuhan and influence the development of neoplasms. Potential antioxidant green tea are directly related to a combination of aromatic rings and hydroxyl groups that make up the structure that causes the binding and neutralization of free radicals by hydroxyl groups.
Polyphenols from green tea inhibit the production of arachidonic acid metabolites such as prostaglandins and leukotrienes, sehinggaakan lower the inflammatory response. Studies in humans and animals have shown the ability of EGCG to block the inflammatory response to UV radiation A and B as well as the ability to inhibit neutrophil migration generally occurs in the inflammatory process.
Although Mechanism is unknown, catechins from green tea showed an increase in Lactobacilli and Bifidobacteria at lowering activity of some pathogens significantly. The study also showed antibacterial effect of green tea against a wide range of gram positive and negative bacteria
Tea polyphenols or catechins are often referred to as a unique substance because it is different catechins found in other plants. Catechins in tea are not tan and do not adversely affect the digestion of food. Tea catechins to be antimicrobial (bacteria and viruses), antioxidants, antiradiasi, strengthen blood vessels, launched urine secretion and inhibits the growth of cancer cells.
Catechins are the main groups of substances of green tea the most influential of all the components of tea. In processing, these colorless compounds, either directly or indirectly, are always associated with all product properties of tea, the flavor, color and aroma.
Catechins are the largest group of components of leaf tea, especially the catechins flavonoids. Tersitesis catechins in tea leaves through the melanic and sikimat acid. While galik acid derived from an intermediate product produced in sikimat acid metabolic pathways.

 

Catechin tea plant is divided into two main groups, namely proanthocyanidin and polyester. Green tea catechins are composed mostly or compounds - compounds catechin, epicatechin, galokatekin, epigalokatekin, epicatechin gallate, galokatekin error, and error epigalokatein. The concentration of catechins is highly dependent on the age of the leaf. Buds and first leaves of the richest catechins error. Catechin levels vary depending on the varieties of the tea plant.

 

http://en.wikipedia.org/wiki/File:Biosynthesis_of_4-hydroxycinnamoyl-CoA.gif

The biosynthesis of catechin begins with a 4-hydroxycinnamoyl CoA starter unit which undergoes chain extension by the addition of three malonyl-CoAs through a PKSIII pathway. 4-hydroxycinnamoyl CoA is biosynthesized from L-phenylalanine through the Shikimate pathway. L-phenylalanine is first deaminated by phenylalanine ammonia lyase (PAL) forming cinnamic acid which is then oxidized to 4-hydroxycinnamic acid by cinnamate 4-hydroyxylase. Chalcone synthase then catalyzes the condensation of 4-hydroxycinnamoyl CoA and three molecules of malonyl-CoA to form chalcone. Chalcone is then isomerized to naringenin by chalcone isomerase which is oxidized to eriodictyol by flavonoid 3’- hydroxylase and further oxidized to taxifolin by flavanone 3-hydroxylase. Taxifolin is then reduced by dihydroflavanol 4-reductase and leucoanthocyanidin reductase to yield catechin. The biosynthesis of catechin is shown below
Leucocyanidin reductase (LCR) uses 2,3-trans-3,4-cis-leucocyanidin to produce (+)-catechin and is the first enzyme in the proanthocyanidins (PA)-specific pathway. Its activity has been measured in leaves, flowers, and seeds of the legumes Medicago sativa, Lotus japonicus, Lotus uliginosus, Hedysarum sulfurescens, and Robinia pseudoacacia.^[21] The enzyme is also present in Vitis vinifera (grape).