Physiochemical properties and antitumor activities of two α-glucans isolated from hot water and alkaline extracts of Cordyceps (Cs-HK1) fungal mycelia

Two novel polysaccharides, WIPS and AIPS, were isolated and fractionated respectively from hot water and alkaline extracts of the mycelial biomass of a medicinal fungus Cordyceps sinensis (strain Cs-HK1). Through analytical and degradation experiments, WIPS and AIPS were characterized as α-d-glucans with a backbone of (1 → 4)-linked α-d-Glcp (>60%) and very similar molecular weights (Mw: WIPS 1180 kDa; AIPS 1150 kDa). WIPS had a short branch of (1 → 6)-linked α-d-Glcp (∼14%), but AIPS was a linear glucan, distinctive from the branched structures of most glucans from medicinal fungi. In aqueous alkaline solutions, both AIPS and WIPS exhibited a random coil structure with the similar conformational parameters but significantly different polydispersity indexes, 0.19 versus 0.37. AIPS exhibited much more significant antitumor and immuno-stimulatory effects than WIPS in animal tests on melanoma tumor-bearing mice.