Rapid identification of gallotannins from Chinese galls by matrix‐assisted laser desorption/ionization time‐of‐flight quadrupole ion trap mass spectrometry

Chinese gall, a conventional traditional Chinese medicine, contains high levels of gallotannins. A rapid method for direct analysis of the gallotannins without using any troublesome sample pretreatments was developed using matrix‐assisted laser desorption/ionization time‐of‐flight quadrupole ion trap mass spectrometry (MALDI‐QIT‐TOF MS) to successfully identify the gallotannin components in the crude extract of Chinese galls within several minutes. The high quality of the MS and MS² spectra acquired clearly showed that hydrolysable tannins in Chinese galls were identified as a series of the gallotannins with degrees of polymerization (DP) of 4–11 galloyl units. The MS² data indicated that the identified gallotannins with DP of 4–7 galloyl units had clear fragmentation with loss of 1–5 galloyl units which were further deprived of 1–3 water moieties. This technique may be used for rapid evaluation and screening of hydrolysable tannins in medicinal plants. Copyright © 2009 John Wiley & Sons, Ltd.