Preparation of a novel glucuronomannan from Auricularia auricala and its immunological activity

A glucuronomannan (AA-4-H, Mw around 4 KDa) was prepared from the fruit bodies of Auricularia auricala by extraction with hot water, deproteination by Sevag reagent, stepwise precipitation with ethanol and partial acid hydrolysis. Monosaccharides analysis revealed that AA-4-H consisted of 91% mannose (Man) and 9% glucuronic acid (GlcA). FT-IR, NMR and methylation analyses indicated that AA-4-H is a branched glucuronomannan. Its main chains are composed of 1, 3-linked alpha-Manp, side chains are single a-Manp or alpha-GlcA residues attached to the O-2 and O-6 of Man residues of the main chains. Bioassay indicated that AA-4-H remarkably enhanced B lymphocyte proliferation and increased the production of nitric oxide of macrophages in vitro. Thus, glucuronomannan AA-4-H could be explored as a potential immunostimulation agent.