Structural elucidation and immuno-stimulatory activity of a novel polysaccharide containing glucuronic acid from the fungus Echinodontium tinctorium

An immuno-stimulatory polysaccharide (EtISPFa) was purified from water extract of the fungus Echinodontium tinctorium. EtISPFa has an estimated weight average molecular weight (M-w) of 1354 kDa and is composed of glucose (66.2 %), glucuronic acid (10.1 %), mannose (6.7 %), galactose (6.4 %), xylose (5.6 %), rhamnose (3.1 %), fucose (1.8 %), and arabinose (0.2 %). It has multiple glycosidic linkages, with 3-Glcp (19.8 %), 4-GlcpA (10.8 %), 6-Glcp (10.7 %), and 3,6-Glcp (8.7 %) being the most prominent. NMR analysis showed that EtISPFa has a backbone containing mostly of 3-substituted beta-glucopyranose with 4-substituted glucopyranosyluronic acid. Short side chains consisting of an average of two beta-glycopyranose residues, connected through 1 -> 6 linkages, are attached to the 6-position of about every 4th or 5th backbone glucose residue. EtISPFa is a novel glucuronic acid-containing beta-glucan capable of significantly inducing the production of cytokines IL-17, IL-16, MIP-2, G-CSF,GM-CSF, LIF, MIP-1 alpha, mip-1 beta, and RANTES in vitro. EtISPFa should be further explored for its immuno-stimulatory activity in vivo.

Automated summary

EtISPFa, an immuno-stimulatory polysaccharide isolated from the fungus Echinodontium tinctorium, exhibits a unique structure and significant inducement of cytokine production in vitro, thus warranting further exploration of its in vivo immuno-stimulatory activity.