Fungal β-glucans have received a lot of interest due to their proinflammatory activity towards cells of the innate immune system. Although commonly described as (1➔3)-β-glucans with varying degree of (1➔6)-branching, the fungal β-glucans constitute a diverse polysaccharide class. In this study, the alkali-soluble β-glucans from the edible mushroom Pleurotus eryngii were extracted and characterized by GC, GC-MS and 2D NMR analyses. The extracts contain several structurally different polysaccharides, including a (1➔3)-β-d-glucan with single glucose units attached at O-6, and a (1➔6)-β-d-glucan, possibly branched at O-3. The immunomodulatory activities of the P. eryngii extracts were assessed by investigating their ability to bind to the receptor dectin-1, and their ability to induce production of the proinflammatory cytokines TNF-α, IL-6 and IL-1β in LPS-differentiated THP-1 cells. Although the samples were able to bind to the dectin-1a receptor, they did not induce production of significant levels of cytokines in the THP-1 cells. Positive controls of yeast-derived (1➔3)-β-d-glucans with branches at O-6 induced cytokine production in the cells. Thus, it appears that the P. eryngii β-glucans are unable to induce production of proinflammatory cytokines in LPS-differentiated THP-1 cells, despite being able to activate the human dectin-1a receptor.

NMR, THP-1, Dectin-1, dispersion, mushroom glucans

13C NMR data:
Linkage	Residue	C1	C2	C3	C4	C5	C6
	bDGlcp	103.3	73.4	76.4	70.0	75.5	68.6


1H NMR data:
Linkage	Residue	H1	H2	H3	H4	H5	H6
	bDGlcp	4.26	3.02	3.19	3.14	3.31	3.59-3.99


1H/13C HSQC data:
Linkage	Residue	C1/H1	C2/H2	C3/H3	C4/H4	C5/H5	C6/H6
	bDGlcp	103.3/4.26	73.4/3.02	76.4/3.19	70.0/3.14	75.5/3.31	68.6/3.59-3.99

There is only one chemically distinct structure:

SVGMWSMILES3D molIonize

 

*OC[C@H]1O[C@@H](*)[C@H](O)[C@@H](O)[C@@H]1O

162.141 g/mol (C₆H₁₀R₂O₅, R = next and previous repeats, not counted in mol weight)