Fragmentation pathways of five characteristic diterpenoid compounds in Isodon coetsa / 中草药

ABSTRACT

Objective To study the fragmentation pathways of five 7,20-cyclo-ent-kaurane diterpenoid compounds (rabdocoetsin B, megathyrin B, rabdocoetsin A, enanderianin N, and megathyrin A) in Isodon coetsa. Methods The samples were analyzed by ultra-high performance liquid chromatography-tandem quadrupole time-of-flight mass spectrometry (UHPLC-Q-TOF-MS2). According to the fragment in MS2 of five compounds, the possible fragmentation pathways of these diterpenoid compounds were inducted. Results In negative mode, the typical fragmentation pathways of these compounds in high-quality areas were mainly loss of substituents on C-1, C-7, and the oxygen bridge on C-20. The fragmentation pathways were different as a result of the difference of the substituents on C-1. The fragment, which in medium and low quality areas, suggested that fracture order of these compounds were A ring to B and then to C ring. Conclusion The study on fragmentation pathways contributed to the structural identification of 7,20-cyclo-ent-kaurane diterpenoid compounds.