Theabrownins in dark tea form complexes with tea polysaccharide conjugates

Abstract

BACKGROUNDTheabrownins (TBs) are one of most important quality components in dark tea, but have not been produced industrially. In this study, the aqueous extract was obtained from Pu'er ripe tea, one kind of dark tea. Caffeine, theaflavin, catechin and saponin were removed by trichloromethane, ethyl acetate and n‐butanol in turn to obtain TBs isolate. The TBs isolate was subjected to column chromatography using a macroporous resin HPD‐750 and eluted with a gradient of 0~700 g·kg‐1 ethanol aqueous solution. four fractions were obtained, and named as TBs‐ FC1, TBs‐ FC2, TBs‐ FC3 and TBs‐ FC4.RESULTSThese four fractions contained polysaccharides and no small molecules such as catechins, caffeine and theaflavins as well as average molecular weights of 123.000 kDa, 23.380 kDa, 89.870 kDa and 106.600 kDa. It was revealed that they were complexes of TBs and tea polysaccharide conjugates (TPC). UV‐Vis and IR spectra showed the properties of TBs and TPC. Their zeta potentials ranged from ‐13.40 mV ̶ ‐38.80 mV in aqueous solutions at pH 3.0‐9.0.CONCLUSIONThis study reveals that TBs does not exist in free state but in combined state in dark tea, which provide theoretical basis for the industrialization of TBs.This article is protected by copyright. All rights reserved.