Theoretical Reaction Model Combined with Characteristic MS2 Information for Systematical Detection and Annotation of Novel Theaflavins in Yunnan Black Tea
In black tea,theaflavins (TFs) are one important class of substances that determine sensory quality and have significant medicinal activities. In addition to the four kinds of common TFs,there may be many other theaflavin analogues (TFAs) with similar chemical structures in tea,but the study on them is very limited. Based on the characteristic sub-structure,mass spectrometry (MS) and MS/MS information,a method for screening and annotation of TFAs from the complex ultra high performance liquid chromatography-high-resolution mass spectrometry (UPLC-HRMS) data was proposed in this work. By analyzing the oxidation and polymerization process of a few TFs,the theoretical reaction model of TFs were summarized,which was used to calculate the precursor ion values of potential TFAs. Meanwhile,the diagnostic fragmentation ions and neutral loss of TFAs according to the fragmentation pathways obtained from chemical standards or documented in literatures were summarized. As a result,36 kinds of compounds were successfully annotated based on the calculated precursor ion values and the MS fragmentation patterns,among which 6 kinds of compounds were reported for the first time in tea. In vitro synthesis experiments were carried out to verified the annotation results. Based on the results of quantitation of 36 kinds of TFAs,a partial least squares-discriminant analysis model was used to investigate the changes of these components during black tea manufacturing. The results indicated that these novel TFAs could be used to effectively distinguish the black tea samples before and after fermentation.
TheaflavinsOxidative condensationMass spectrometryNeutral lossFragmentation ion
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