Effects of season and plantation on phenolic content of unfermented and fermented Sri Lankan tea.

The effects of season and plantation on the polyphenol content of Camellia sinensis (tea) leaves were determined. Aqueous and organic extracts of freeze-dried fresh (unfermented) and black (fully-fermented) tea leaves were prepared for a structured set of samples (fermented and unfermented teas from six high-, mid- and low-grown plantations; fermented and unfermented teas from two harvesting seasons from four highland plantations), collected from the main tea-growing regions in Sri Lanka. Total catechin content and amounts of individual catechins, flavonols and theaflavins were determined by HPLC. Mean values for the phenolic constituents were generally significantly higher (p<0.05) with solvent extraction. The mean values for total catechins, total flavonols and caffeine in the aqueous extracts from unfermented teas were 10.6%, 1.5% and 2.9%, respectively. For both unfermented and fermented tea leaves, a significant (p<0.05) interaction between plantation and season was observed for phenolic constituents. Ferric reducing antioxidant power was positively (p<0.05) correlated with (-)-epicatechin gallate and total phenolic contents.