|Harnly, James - Jim|
Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/1/2008
Publication Date: 9/10/2008
Citation: Lin, L., Harnly, J.M. 2008. New phenolic components and chromatographic profiles of green and fermented teas. Journal of Agricultural and Food Chemistry. 56(17):8130-8140. Interpretive Summary: This paper presents detailed identification of the flavonoids and other phenolic compounds found in green and fermented teas. More than 30 of these compounds are reported for the first time. Based on these phenolic profiles it is possible to group all the teas into 5 general categories. Each category possesses slightly different flavonoid and phenolic acid components. This information will be helpful in establishing the potential benefits of commonly consumed teas to human health.
Technical Abstract: A standardized profiling method based on liquid chromatography with diode array and electrospray ionization/mass spectrometric detection (LC-DAD-ESI/MS) was applied to establish the phenolic profiles of 41 green teas and 25 fermented teas. More than 80 phenolic compounds were either identified that allowed the teas to be organized into 5 groups. Epigallocatechin gallate (EGCG) was the major phenolic component of green tea made from mature leaves (group-1) while green tea made from the younger buds and leaves (group-2) contained lower concentrations of flavonoids. Partially fermented teas (group-3) contained half EGCG content of the green tea. Fully fermented black teas (group-4) had only a trace of EGCG, but contained theaflavins. Highly over-fermented black tea (group-5) contained only trace amounts of glycosides and theaflavins. Over 30 phenolic compounds are reported for the first time in tea and this is the first phenolic profile to simultaneously detect C- and O-glycosylated flavonoids, catechins, proanthocyanins, phenolic acid derivatives, and purine alkaloids.