STUDIES OF POLYMER POLYPHENOLS IN TEA

Polymer tea polyphenols (thearubigins = TR) were isolated from a black tea brew by ultrafiltration. The fraction of relative molecular mass (M(r)) > 5000 was examined using liquid chromatography. A partial separation of the TR fraction could be achieved by reversed-phase (RP)-HPLC and by gel-filtration chromatography, but not a complete separation into distinct peaks. After hydrolysis, the anthocyanidins delphinidine and cyanidine and some flavone-C-glycosides were detected. The amount of cyanidine was 0.26% (in the TR fraction M(r) > 5000). Gallic acid moieties were also determined after hydrolysis: the amounts were about 2.5% (in the TR fraction mentioned above). An HPLC separation system from the literature was employed to analyse the stability and extraction behaviour of the TR. An extract prepared by a 2-h Soxhlet extraction contained only small amounts of TR compared with a tea brew prepared by a normal 10 min extraction. This is due to incomplete extraction, not to destruction. Hot-plating the 10-min extract (90-degrees-C, 2 h) led to a decrease in the peak areas of theaflavin (TF) and other pigments.