Discrimination of raffinose and planteose based on porous graphitic carbon chromatography in combination with mass spectrometry

Raffinose and planteose are non-reducing, isomeric trisaccharides present in many higher plants. Structurally,
they differ in the linkage of α-D-galactopyranosyl to either glucose C(6) or to C (6′ ) of fructose, respectively and
thus differentiating each other is very challenging. The negative ion mode mass spectrometric analysis is shown
to distinguish planteose and raffinose. However, to facilitate the robust identification of planteose in complex
mixtures, herein, we have demonstrated the use of porous graphitic carbon (PGC) chromatography combined
with QTOF-MS2 analysis. The separation of planteose and raffinose was achieved on PGC, wherein both have
recorded different retention time. Detection through MS2 analysis revealed the specific fragmentation patterns
for planteose and raffinose that are distinctive to each other. The applicability of this method on oligosaccharides
pool extracted from different seeds showed clear separation of planteose that allowed unambiguous identifica-
tion from complex mixtures. Therefore, we propose PGC-LC-MS/MS can be employed for sensitive, throughput
screening of planteose from wider plant sources.