A liquid chromatography-electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS)-based dereplication method has been developed for identifying oplopane- and bisabolane-type sesquiterpenoids from Tussilago farfara L. [1-3]. This method used sequential MS scanning modes to identify fragmentation patterns of common skeletons and their derivatives. In the positive ion mode, product ion scanning for ions with m/z 215, 217, 229, or 231 yield same fragmentation pattern, respectively, indicating that ions with m/z 215 and 217 were diagnostic cation of oplopane sesquiterpnoids, and m/z 229 and 231 were those of bisabolane sesquiterpenoids. The difference of two cations (m/z 215 versus 217 or m/z 229 versus 231) is the number of the ester-linkages. Since the cleavage of ester linkage dominantly undergoes a double bone reduction, the cations with m/z 217 (oplopane) and 231 (bisabolane) were caused from two cleavages of ester bond and the cations with m/z 215 (oplopane) and 229 (bisabolane) were derived from three cleavages. Secondly, precursor ion and neutral loss scanning for the cation with m/z 215, 217, 229, and 231 yield diagnostic fragmentation patterns and identified which moieties is linked to the common skeletons. The fragmentation patterns suggest parental and intermediate cations with specific m/z values.
References
[1] Kikuchi M, Suzuki N. Chem Pharm Bull 1992; 40(10): 2753-2755
[2] Yaoita Y, Suzuki N, Kikuchi M. Chem Pharm Bull 2001; 49(5): 645-648
[3] Li W, Huang X, Yang XW. Fitoterapia 2012; 83: 318-322