A HPLC-ESI-Q-ToF-MS method for the analysis of monomer constituents in PHGG, gum arabic and psyllium husk prebiotic dietary fibre supplements

“Soluble” type dietary fibre contains polysaccharides with monomer constituents that play a major role in lowering the glycemic index of food (“low-GI”) and improving colonic health through gut microbiome fermentation. Soluble fibres such as partially hydrolysed guar gum (PHGG), gum Arabic and psyllium husk are of particular interest in gastrointestinal research, exploring their effects in motility disorders such as gastroparesis, constipation, diarrhea and irritable bowel syndrome (IBS) is important. The primary aim of this research was to develop a rapid pre-column derivatized HPLC-ESI-Q-ToF-MS method for the identification and quantification of monomer sugar constituents in commercial dietary fibre supplements of PHGG, gum Arabic and psyllium husk. Polysaccharides in the samples were hydrolysed and derivatized using 1-phenyl-3-methyl-5-pyrazolone (PMP). A rapid 21 min HPLC-ESI-Q-ToF-MS method separated nine different PMP-labelled monomer sugars. Five different sugars (i.e., Galactose, Arabinose, Rhamnose, Mannose and Xylose) were identified and quantified. Standard curve linearity was excellent (R2 > 0.999), with good intra-laboratory precision (< ±5% SD for concentrations, ≤ ±0.02 min peak shifting for retention times). The average three-level (50%, 75% and 100%) spiking recoveries for the analytes was acceptable (96.22–109.49%). Positive scanning mode ESI-MS/MS was used to generate [M + H]+ precursor ions and three (m/z) product ion fragments to provide identity confirmation. The concentrations of monomer sugars in gum Arabic and psyllium husk dietary fibres were consistent with literature reports. In PHGG, the concentration of galactose was unexpectedly higher than mannose, indicating that the commercial hydrolysis process of guar gum during PHGG manufacturing affected monomer composition. The method presented here provides the basis for the standardisation and labelling of commercial PHGG, gum Arabic and psyllium husk supplements. Future research will need to explore the monomer variability in other prebiotic soluble fibres and their efficacy in the production of beneficial short-chain fatty acids (SCFA) in the colonic environment.