Rapid profiling and identification of triterpenoid saponins in crude extracts from Albizia julibrissin Durazz. by ultra high-performance liquid chromatography coupled with electrospray ionization quadrupole time-of-flight tandem mass spectrometry

Ultra high-performance liquid chromatography coupled with electrospray ionization quadrupole time-of-flight tandem mass spectrometry (UHPLC/ESI-Q-TOF-MS/MS) was applied to separate and identify triterpenoid saponins in crude extract from the stem bark of Albizia julibrissin Durazz. The molecular weights were determined by comparing quasi-molecular ions [M+NH4]+ in positive mode and [M−H]− and [M−2H]2− ions in negative mode. The MS/MS spectra of the [M−H]− ions for saponins provided a wealth of structural information related to aglycone skeletons, sugar types and linked sequence. On the basis of the fragmentation behavior of known saponins isolated before, saponins from this plant were identified, even though references were not available. As a result, a total of twenty-eight saponins in the crude extract were identified, which all had a common basic skeleton of the triterpene oleanolic acid and eight of them were new compounds.