Enzymic activity Epicatechin

In 2005, the inhibition of monoamine oxidase B (MAO-B) of a phenethylamine selective metabolism enzyme or dopamine selective metabolism enzyme by (-)-epicatechin (1) was examined. Because, it could be expected that the attenuation of monoamine oxidase B (MAO-B) activity might provide the protection against the oxidative neurodegeneration. Actually, the inhibition of monoamine oxidase B (MAO-B) activity has been used as part of the treatment of Parkinson s and Alzheimer s patients. 

Rodgers, E and Grant, M (1998) The effect of the flavonoids, quercetin, myricetin and epicatechin on the growth and enzyme activities of MCF7 human breast cancer cells. Chem. Biol. Interact, 116, 213-228. 

The anthocyanidin reductase enzyme recently described in Arabidopsis and Medicago was shown to be present in tea with very high activity and could produce epicatechin as well as epigallocatechin from the respective anthocyanidins, thus explaining very high contents of llavan-3-ols. Especially, two enzymes, dihydroflavonol 4-reductase and leucoanthocyanidin 4-reductase selectively catalyze key steps in their biosynthesis of catechins (43,62) and gallocatechins (63,64), respectively (Fig. 14) [31]. 

The flavones and catechins seem to be the most powerful flavonoids for protecting the body against ROS. Epicatechin and rutin are also powerful free-radical scavengers. Xanthine oxidase enzyme is a source of oxygen-free radicals. The scavenging ability of rutin, quercetin, and silibin may be due to its inhibitory effect on xanthine oxidase activity, thereby resulting in decreased oxidative injury [60]. 

Dehydroshikimate reductase which reversibly interconverts dehydroshikimate and shikimate is a key enzyme in the biosynthesis of phenolic compounds via the phenylalanine pathway. Phenylalanine ammonia-lyase which catalyzes the cleavage of phenylalanine into transcin-namate and NH3, is equally important for the biosynthesis of phenols. Its activity in tea leaves parallels the content of catechins and epicatechins. 

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