Differentiation between 3,4-and 4,15-Epoxyeudesmanolides by Electrospray Ionization Tandem Mass Spectrometry

We investigated the fragmentation of the eudesmanolide-type sesquiterpene lactones 1α-(4-hydroxymethacryloyloxy)-3α,4α-epoxy-8α-hydroxyeudesm-11(13)-6α,12-olide (1) and 1α-(2,3-epoxyangeloyloxy)-4α,15-epoxy-8α-hydroxyeudesm-11(13)-6α,12-olide (2) by electrospray ionization tandem mass spectrometry (esi-ms/ms). the elimination of the different ester substituent at c(1) directly from protonated 1 and 2 (a) led to the formation of two regioisomer product ions b (a-rco2h). further fragmentation of b resulted from consecutive eliminations of h2o and co molecules. however,we identified four product ions that allowed for the differentiation between 3,4-and 4,15-epoxyeudesmanolides. the formation of these diagnostic ions was associated with the c(3)-o bond of compound 1,which propitiates the participation of the lone pair of the oxygen epoxide in the formation of b through a grob-wharton-type fragmentation,then resulting in an alternative fragmentation pathway. these data can be useful for the fast differentiation between epoxyeudesmanolide regioisomers directly from dimerostemma extracts by liquid chromatography-tandem mass spectrometry (lc-ms/ms),as an alternative to nmr,or even for quantitation studies of these compounds using multiple reaction monitoring (mrm) scan. © 2017 herbert júnior dias et al.