Chromatography and mass spectrometry-based approaches for perception of polysaccharides in wild and cultured fruit bodies of Auricularia auricular-judae.

Auricularia auricular-judae polysaccharides (AAPs) have been accepted as one important biological constituent. Quality analysis of A. auricular-judae is generally difficult due to technical issues in separating and detecting AAPs. Here, we describe a stepped chromatographic and mass spectrometric approach for discrimination and characterization of AAPs. HPSEC-MALLS-RID and GC-MS techniques have earlier been shown to be ineffective in evaluating wild and cultured AAPs based on molecular weight distributions and monosaccharide compositions. Nevertheless, direct ESI--MS oligosaccharide fingerprints coupled with PCA have the remarkable ability to discriminate wild and cultured ones. HILIC-UPLC-ESI--MS has indicated that wild and cultured AAPs have distinct peak number and intensities in mild acid hydrolysates. HILIC-UPLC-ESI--HCD-MS/MS was further applied in deducing interglycosidic linkages and sequence of monosaccharide residues in oligosaccharides. We demonstrate that linear GlcAw → Hexm → GlcAx → Hexn → GlcAy → Hexp → GlcAz → Hexq → (w, x, y, z = 0, 1; m, n, p, q ≥ 0; Hex1 → 6Hex, GlcA1 → 4Hex, Hex1 → 4GlcA) was constructed as the general skeleton of AAPs based on C- and B-type ions as well as cross-ring cleavage A-type series ions. The established workflow has been confirmed to be a feasible approach for comprehensive characterization of polysaccharides in foods and plants.