Determination of solanidine- and tomatidine-type glycoalkaloid aglycons by gas chromatography/mass spectrometry

A combined derivatization method for gas chromatographic/mass spectrometric (GC/MS) analysis of steroidal glycoalkaloid (SGA) aglycons was developed using both trimethylsilylation and pentafluoropropionylation. In comparison with underivatized or only silylated aglycons, the new technique produces more specific and abundant fragmentation for compounds with a tomatidine-type structure. For example, the difference between solasodine and tomatidine, the former containing a double bond at position 5,6 in the steroidal skeleton, can be observed by their base peak fragments at m/z 417 (C24H41O2Si2) and m/z 419 (C24H43O2Si2). The method is well suited for the simultaneous determination of both solanidane- and spirosolane-type SGA aglycons from Solanum species and hybrids. The reproducibility of the method, including SGA extraction, hydrolysis, derivatization, and quantitative GC/MS analysis, was <6% (CV) for the principal aglycons determined from a hybrid between a wild potato species, Solanum brevidens Phil., and a cultivated potato, S. tuberosum L. A single ion monitoring technique using specific fragments m/z 419 and 417 could be applied for the determination of minor stereoisomers, which are often overlapped by large amounts of tomatidine.