Conformational properties and biological activities of α-D-mannan from Sanghuangporus sanghuang in liquid culture

Sanghuang is a well-known edible and medicinal fungus consumed in Asia for centuries. In the present study, a novel exopolysaccharide named as mannan (SSEPS2) was isolated from the liquid culture broth of Sanghuangporus sanghuang by using ethanol precipitation, anion-exchange chromatography, and size-exclusion chromatography, which was exclusively composed of D-mannose with the molecular weight 9.43 × 104 g/mol. The structural analysis suggested that SSEPS2 consisted of 1,3-linked and 1,2-linked α-D-mannopyranose (Manp), with substitution at O-6 of 1,2-linked α-D-Manp by 1,6-linked α-D-Manp residues and terminal α-D-Manp residues. The exponent of α (0.58) indicated that SSEPS2 existed in a flexible chain conformation, with a coil-like structure in 0.1 M NaNO3 at 25 °C, which was further confirmed by the atomic force microscopy images and a three-dimensional molecular model. It exhibited potential antitumor activity against the growth of HepG2 (human hepatoma) and MCF-7 cell lines in vitro. The IC50 values for inhibiting HepG-2 cells and MCF-7 cells proliferation were 365 and 340 μg/mL, which showed its potential application in the development of anticancer therapeutics.