Structure and Chain Conformation of Bioactive β-D-glucan Purified from Water Extracts of Ganoderma Lucidum Unbroken Spores

Two polysaccharide fractions (GLSB50 and GLSB70) with total sugar content of 82.07 wt% and 53.79 wt%, respectively, were obtained from the water extracts of unbroken Ganoderma lucidum spores by sequential ethanol precipitation treatment. Compared with GLSB70, GLSB50 exhibited better activity on stimulation of humoral immune responses in immunosuppressed mice. A novel β-D-glucan (GLSB50A-III-1) with weight average molecular weight (M) of 1.93 × 10 g/mol was purified from GLSB50 through chromatography separation. The exponent α value of Mark-Houwink-Sakurada equation was calculated to be 0.13, indicating that GLSB50A-III-1 presented globular spheres conformation in aqueous solution. Structural analysis showed that GLSB50A-III-1 mainly consisted of (1 → 3), (1 → 4), (1 → 6)-linked β-d-glucose residues in the backbone, with two single β-D-Glcp attached at O-6 of β-(1 → 3) and β-(1 → 4)-linked residues separately as side chains. The repeat unit of GLSB50A-III-1 was deduced as follows.