Electrospray tandem mass spectrometric analysis of duboscic acid, exploring the structural features of a new class of triterpenoids, dubosane

Duboscic acid belongs to a new class of triterpenoids dubosane, isolated from Duboscia macrocarpa. Gas-phase fragmentation of duboscic acid was studied using positive ion electrospray ionization quadropole time-of-flight mass spectrometry (ESI-QqTOF-MS/MS) hybrid instrument. ESI-QqTOF-MS (positive ion mode) showed the presence of the protonated molecule [M+H]+ which under low-energy collision-induced dissociation tandem mass spectrometric (CID-MS/MS) analysis showed the characteristic losses of methoxy, hydroxyl and carboxylic groups. Our results demonstrated the characteristic fragments of this new class of triterpenoids which are formed due to the cleavage of seven membered unsaturated ring C. The fragmentation pathways of characteristic fragments were proposed with the aid of HRMS and computational studies. The knowledge of the fragmentation pattern and key fragment ions of duboscic acid, i.e. gas phase fragmentation behavior of unique dubosane structure, will be useful for further exploration of the related species of the same genera for the characterization of novel members of this class of compounds.

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► First report on CID-MS/MS analysis of dubosane triterpenoid, duboscic acid.
► Identification of key fragments and proposal of logical fragmentation pathways.
► Characteristic fragments are formed due to the cleavage of seven membered ring C.