Plants of the Solanum genus contain steroid saponins and steroid alkaloid glycosides of which members with
spirostan skeleton predominate i.a. in the species of S. dulcamara and S. villosum. Due to variations in their sugar chain and aglycon modifications, these compounds
can occur in large numbers and cover a wide range of molecular weights, which impedes
the planning of MS/MS scans in metabolic profiling of these species using HPLC-qTOF-ESIMS.
In addition, protonated or ammoniated molecules of steroid saponins often show low
relative abundancies and are therefore frequently ignored by data-dependent MS/MS
procedures, whereas the very abundant protonated molecules of steroid alkaloid glycosides
have proven themselves surprisingly stable and give only poor product ion yields.
Using the steroid saponin degalactotigonin and the steroid alkaloid glycoside α-tomatine,
we studied high resolution mass and product ion spectra of different precursor ions
which for their abundance are likely to be selected by data-dependent MS/MS procedures.
The spectra were analyzed for their informative value towards characterizing sugar
chains and aglycons. Problems and pitfalls in the interpretation of the spectra are
highlighted and include biased isotope patterns, isobaric product ions, and internal
residue loss in the dissociation of the sugar chain. The presented results are intended
to aid the metabolic profiling of Solanum samples by HPLC-MS.
