Catechins biological activities

Biological Activity of Catechins and Proanthocyanidins Other than Antimicrobial Activity... 

Astringency in green tea (Japanese tea) is due to catechins, which are a kind of condensed tannins. The largest source is various teas derived from the tea plant Camellia sinensis. Catechins have various biological activities,... 

At present, the biological activity of tea catechins has been determined mostly with the parent chemicals. EGCG, EGC, EC, and ECG have been shown to possess various biological activities, including antioxidative and free radical scavenger activity when studied in in vitro systems. " Pietta et al. reported that free plasma catechins account for only about 20% of increase in the total antioxidant activity... 

Some tea catechin metabolites have been identified in humans after oral ingestion, including the glucuronide, sulfate, and methylation forms of catechins and their microbial metabolites. Some of these metabolites have higher plasma concentrations than their parent compounds. However, the structures of other metabolites of tea catechins still need to be identified, and bioavailability of catechins in humans still needs to be determined in order to understand the biological activities of tea catechins in vivo. 

Considerable interest has developed in the past decade in unraveling the beneficial health effects of tea, particnlarly in its polyphenolic components and its antioxidant activity. Catechins, theaflavins, and thearnbigins are three important gronps of polyphenols present in tea. The formation mechanism of these componnds dnring tea processing as well as their respective biological activities are of great importance and of scientific and commercial interest. 

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