Novel analysis procedure for red ginseng polysaccharides by matrix-assisted laser desorption/ionization time-of-flight/time-of-flight mass spectrometry

BACKGROUND: Red ginseng polysaccharides (RGPs) have been acknowledged for their outstanding immunomodulation and anti-tumor activities. However, their studies are still limited by the complexity of their structural features, the absence of purification and enrichment methods, and the rarity of the analytical instruments that apply to the analysis of such macromolecules. Thus, this study is an attempt to establish a new mass spectrometry (MS)-based analysis procedure for RGPs. METHODS: Saponin pre-excluded powder of RG (RG-SPEP, 10 mg) was treated with 200 μL of distilled water and centrifuged for 5 h at 1000 rpm and 85 °C. Ethanol-based precipitation and centrifugation were applied to obtain RGPs from the heated extracts. Further, endo-carbohydrase treatments were performed to produce specific saccharide fragments. Solid-phase extraction (SPE) processes were implemented to purify and enrich the enzyme-treated RGPs, while matrix-assisted laser desorption/ionization time-of-flight/time-of-flight (MALDI-TOF/TOF) MS was employed for the partial structural analysis of the obtained RGPs. RESULTS: Utilizing cellulase, porous graphitized carbon (PGC), hydrophilic interaction chromatography (HILIC), and MALDI-TOF/TOF MS, the neutral and acidic RGPs were qualitatively analyzed. Hex(n) and Hex(n)−18 (cellulose analogs) were determined to be novel neutral RGPs. Additionally, the [Unknown + Hex(n)] species were also determined as new acidic RGPs. Furthermore, HexA(n) (H) was determined as another form of the acidic RGPs. CONCLUSION: Compared to the previous methods of analysis, these unprecedented applications of HILIC-SPE and MALDI-TOF/TOF MS to analyze RGPs proved to be fairly effective for fractionating and detecting neutral and acidic components. This new procedure exhibits great potential as a specific tool for searching and determining various polysaccharides in many herbal medicines.