GLYCOSIDES IN Viola Tricolor L.

CHAPTER 2: INTRODUCTION
4-ketoand5-OHgroups,the4-ketoand3-OHgroups,andthe3’-OHand4’-OH
groups. Positionalflavonoidglycosideisomers,whichpossesstheabovechela-
tion sites could be differentiated based on the different fragmentation of their
Ca(II) or Mg(II) complexes [134]. Reportedly, the C-7 glycosylated isomer ex-
hibited the most pronounced fragmentation and 0,2 X + as distinctive fragment.
The C-4’ isomer implied characteristic loss of the aglycone portion, while the
C-3isomershowedonlythelossofasugarmoiety. Thisloss,however,wastyp-
icalfortheotherisomersaswell. Basedon thisapproach 6-and8-C-glycosides
could also be distinguished. Moreover, the formation of Co(II)complexes with
the use of 4,7-diphenyl-1,10-phenanthroline as a new auxiliary chelating lig-
and,providedmeansofdeterminationfortheglycosidiclinkagetype,sincethe
loss of the aglycone plusrhamnose unit wasobserved onlyfor the 1→2isomer
rhoifolin (apigenin-3-O-rhamnosyl(1→2)glucoside) [135]. Similarly, additional
diagnostic fragmentation paths were reported for the 1→2 isomers in the case
ofaluminum complexes [136].
2.4.3.6 MSanalysis of anthocyanins
According to the few mass spectrometric analysis reports in the literature, an-
thocyanidins (the aglycones) have similar fragmentation characteristics as the
above discussed flavonoid classes. Their positive ion MS/MS spectra show
fragments resulted from small molecule losses and C-ring cleavages reported
byOliveiraetal.[137]. Thispaperclearlyexplains,howthenumberandnature
of substituents, connected to the basic anthocyanidin skeleton, can be deter-
mined from the molecular masses of the characteristic 0,2 B + , 0,2 B + –CO, 0,3 A + ,
0,2 A +• fragments. Analysis of the anthocyanins (the glycosides) demonstrated
thattheyalsoproducedtheabovediscussed i,j X + andYi + fragments[137–141].
In addition, the loss of a 15 Da unit (CH3 • ) was reported to be distinctive for
methoxy group containing anthocyanidins [137, 140].
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