Characterisation of glucosinolates using electrospray ion trap and electrospray quadrupole time-of-flight mass spectrometry.
Twelve naturally occurring glucosinolates displaying alkenyl, hydroxylated, methylsulphinyl, aromatic and indole side chains were investigated by both negative and positive ion electrospray ionisation-tandem mass spectrometry (ESI-MS/MS). In order to resolve the MS/MS spectra obtained from the anion and cation molecular ions of glucosinolates, the different fragments were investigated by MSn experiments using an ion trap spectrometer. The MS3 spectra obtained permitted possible fragmentation schemes to be proposed. These were supported by accurate mass measurements of some characteristic diagnostic ions with the help of a quadrupole time-of-flight instrument. The negative ion ESI-MS/MS behaviour of the different glucosinolates investigated in this study confirmed previously described patterns and revealed new interesting structural informative fragments. Some are common to all the glucosinolates and others are highly specific for a type of variable side chain. The positive ion ESI-MS/MS fragments obtained from the [MNa+Na]+ or [MK+K]+ molecular ions did not provide complementary specific diagnostic ions. Nevertheless, when compared with the negative ion mode, the daughter ions appeared more homogenous and with a better relative abundance for all of the 12 compounds studied. Moreover, the positive ion mode appeared to be more efficient than the negative mode for the study of methoxylated glucosinolates and should be useful to detect the glucosinolates present as organic salts in crude plant extracts.
Fabre
Nicolas
N
UMR 152 UPS/IRD, Pharmacochimie des Substances Naturelles et Pharmacophores Redox, Université Paul Sabatier Toulouse III, Faculté des Sciences Pharmaceutiques, 31062 Toulouse Cedex 09, France. nfabre@cict.fr
Poinsot
Véréna
V
Debrauwer
Laurent
L
Vigor
Claire
C
Tulliez
Jacques
J
Fourasté
Isabelle
I
Moulis
Claude
C
D005961:Glucosinolates / Q000032:analysis* / Q000737:chemistry*; D015394:Molecular Structure; D021241:Spectrometry, Mass, Electrospray Ionization
D005961:Glucosinolates