Changes in major polyphenolic compounds of tea (Camellia sinensis) leaves during the production of black tea.

The objective of this study was to quantify the polyphenolic compounds present in tea samples during black tea processing, and to determine the correlation between the contents of individual catechins and theaflavins. Nine monomeric and four dimeric compounds were identified and quantified by HPLC. During black tea processing, the catechins content decreased, whereas the gallic acid content increased. The decrease in the catechins-in particular, the cis-catechins-was due to the formation of dimeric theaflavins. In the present study, we found a significant negative correlation between the changes in the catechins and theaflavins contents during black tea processing. Theaflavin-3-gallate showed the strongest correlations with the cis-catechins ((-)-epigallocatechin: r=0.713; (-)-epicatechin: r=0.755; (-)-epigallocatechin gallate: r=0.681; and (-)-epicatechin gallate: r=0.771).