Analysis on Fragmentation Patterns and Diagnostic Ions of Two Types of Euphorbia Diterpenoid by High-resolution Tandem Mass Spectrometry

KeyWord:Euphorbia diterpenoid  myrsinane-type  premyrsinane-type  fragmentation pattern  diagnostic ions

Abstract:

      Tandem mass spectrometry£¨MS/MS£© generates fragmentation ions from quasi-molecular ions£®Meanwhile£¬high-resolution mass spectrometry offers an accurate mass measurement£¬which is particularly suitable for the analysis of fragmentation pathways and structure identification of natural products£®In this paper£¬fifteen natural compounds of Euphorbia diterpenoid£¬classified as myrsinane-type£¨1£­9£© and pemyrsinane-type£¨10£­15£© possessing chemical structural features of 5/7/6/3 and 5/7/6 ring fused system£¬were selected to analyze the basis of characteristic MS/MS fragmentation patterns£®Experimental data indicated that diterpenoid backbone fragments were yielded by continuous acids£¬carboxylates elimination and dehydration upon higher-energy collision dissociation£¨HCD£©£®Compounds 1£­7 fragmented to yield backbone ions of m/z 311£¨ion A£© and m/z 293£¨ion B£©£¬compounds 8 and 9 gave at m/z 295£¨ion C£© and m/z 277£¨ion D£©£¬and similarly£¬compounds 10£­15 showed them at m/z 313£¨ion E£© and m/z 295£¨ion F£©£®A series of diagnostic ions including backbone ions in the low mass region of m/z 200£­320 were identified£¬which were associated with specific structural features£®The neutral losses of H2O£¬HCHO£¬CO£¬C3H4 and/or acetone were the characteristic eliminations from the backbone precursor ions due to the presence of hydroxyl£¬THF£¨tetrahydrofuran£© ring£¬carbonyl£¬isopropenyl and/or CH3C£¨OH£©CH3 units in the structures£®The occurrence of key diagnostic ions and their fragmentation patterns could potentially permit the chemical structure determination and the identification for unknowns.