Structure of an unprecedent glucuronoxylogalactoglucomannan from fruit bodies of Auricularia auricula-judae (black woody ear)

An unprecedent glucuronoxylogalactoglucomannan (GXG ' G '' M), ME-2 (Mw, 2.60 x 105 g/mol; O-acetyl % = 16.7 %), was isolated and purified from water extracts of Auricularia auricula-judae (black woody ear). Firstly, due to much higher O-acetyl contents, we prepared its fully deacetylated products (dME-2; Mw, 2.13 x 105 g/ mol) for convenient structure survey. The repeating structure-unit of dME-2 was readily proposed based on Mw determination, monosaccharide compositions, methylation analysis, free-radical degradation and 1/2D NMR spectroscopy. The dME-2 was identified as a highly branched polysaccharide with an average of 10 branches per 10 sugar backbone units. The backbone was only repeating -> 3)-alpha-Manp-(1 -> residues, substituted at the C-2, C-6 and C-2,6 positions. The side chains included beta-GlcAp-(1 ->, beta-Xylp-(1 ->, alpha-Manp-(1 ->, alpha-Galp-(1 -> and beta-Glcp(1 ->. Secondly, the complex substituted positions of O-acetyl groups in ME-2 were determined to be at C-2, C-4, C-6 and C-4,6 in the backbone and at C-2 and C-2,3 in some side chains. Finally, the anti-inflammatory activity of ME-2 was preliminarily explored on LPS-stimulated THP-1 cells. The above date not only provided the first example for structural studies of GXG ' G '' M type polysaccharides, but also facilitated development and application of black woody ear polysaccharides as medicinal agents or functional dietary supplements.

Automated summary

A previously unknown glucuronoxylogalactoglucomannan (GXG ' G '' M), named ME-2, was isolated and purified from water extracts of Auricularia auricula-judae. ME-2 is a highly branched polysaccharide with an average of 10 branches per 10 sugar backbone units. ME-2 also exhibited anti-inflammatory activity. These findings contribute to the development and application of black woody ear polysaccharides as medicinal agents or functional dietary supplements.