Identification of trimeric and tetrameric flavan-3-ol derivatives in the SII black tea thearubigin fraction of black tea using ESI-tandem and MALDI-TOF mass spectrometry

摘要

Direct infusion MS~n and MALDI-TOF-mass spectrometry were applied for characterizing thearubigins isolated from black tea. Components of the so-called SII fraction of thearubigins obtained through caffeine precipitation were studied exclusively. New components with molecular weights higher than 1000 Da were analyzed and structurally characterized. The data generated revealed clearly the presence of different trimeric and tetrameric flavan-3-ols formed through oxidative coupling between flavan-3-ols and their dimers, most notably theaflavin and theasinensin within the black tea thearubigins. Our data are fully consistent with the oxidative cascade hypothesis of thearubigin formation and provide for the first time experimental evidence on oxidative oligomer-ization of flavan-3-ols and their dimers to form oligomeric flavan-3-ols.