Structural studies of immunomodulatory (1 → 3)-, (1 → 4)-α glucan from an edible mushroom Polyporus grammocephalus

A water soluble polysaccharide (PGPS) with molecular weight ~ 1.4 × 10⁵ Da was isolated by alkali treatment from an edible mushroom Polyporus grammocephalus and purified by gel chromatography using sepharose-6B column. Monosaccharide analysis revealed that PGPS was made up of glucose only. PGPS contained (1 → 3)-α-D-Glcp and (1 → 4)-α-D-Glcp moieties in a molar ratio of nearly 1:2. Through a series of chemical and spectroscopic (1D/2D NMR) investigations, the repeating unit of the glucan was established as: →3)-α-D-Glcp(1 → [4)-α-D-Glcp(1]₂→ This α-glucan was observed to stimulate some prime components of immune system, namely, macrophages, splenocytes, and thymocytes.