Analysis of the monosaccharide composition of water-soluble polysaccharides from Sargassum fusiforme by high performance liquid chromatography/electrospray ionisation mass spectrometry

•A precolumn derivatization LC/ESI–MS method was established for the analysis of polysaccharides in Sargassum fusiforme.•The optimisation of the pre-column derivatization process was studied.•Six monosaccharides from S. fusiforme polysaccharide were tentatively identified. Sargassum fusiforme (hijiki) is the well-known edible algae, whose polysaccharides have been proved to possess interesting bioactivities like antitumor, antioxidant, antimicrobial and immunomodulatory activities. A facile and sensitive method based on high-performance liquid chromatography method of pre-column derivatization with 1-phenyl-3-methyl-5-pyrazolone (PMP) coupled with electrospray ionisation mass spectrometry (HPLC/ESI–MS) has been established for the analysis of the monosaccharide composition of polysaccharides in S. fusiforme. Monosaccharides have been converted into PMP-labelled derivatives with aqueous ammonia as a catalyst at 70°C for 30min. The optimisation of the pre-column derivatization process was studied. The LODs of the monosaccharides were in the range from 0.01 to 0.02nmol. PMP-labelled mixture of monosaccharides has been well separated by a reverse-phase HPLC and detected by on-line ESI–MS method under optimised conditions. The mobile phase of elution system was chosen as acetonitrile (solvent A) and 20mM aqueous ammonium acetate (solvent B) (pH 3.0) with Zorbax XDB-C18 column at 30°C for the separation of the monosaccharide derivatives. Identification of the monosaccharides composition was carried out by analysis with mass spectral behaviour and chromatography characteristics of 1-phenyl-3-methyl-5-pyrazolone (PMP) labelled monosaccharides. All PMP-labelled derivatives display high chemical stabilities, whose regular MS fragmentation is specific for reducing labelled sugars. The result showed that the S. fusiforme polysaccharide consisted of mannose, glucose, galactose, xylose, fucose and glucuronic acid or galacturonic acid, or both uronic acids.