Polysaccharides from Basidiocarps of the Polypore Fungus Ganoderma resinaceum: Isolation and Structure

In this study, we focused on the isolation and structural characterization of polysaccharides from a basidiocarp of polypore fungus Ganoderma resinaceum. Polysaccharide fractions were obtained by successive extractions with cold water at room temperature (20 degrees C), hot water under reflux (100 degrees C), and a solution of 1 mol L-1 sodium hydroxide. The purity of all fractions was controlled mainly by Fourier transform infrared (FTIR) spectroscopy, and their composition and structure were characterized by organic elemental analysis; neutral sugar and methylation analyses by gas chromatography equipped with flame ionization detector (GC/FID) and mass spectrometry detector (GC/MS), respectively; and by correlation nuclear magnetic resonance (NMR) spectroscopy. The aqueous extracts contained two main polysaccharides identified as a branched O-2-beta-d-mannosyl-(1 -> 6)-alpha-d-galactan and a highly branched (1 -> 3)(1 -> 4)(1 -> 6)-beta-d-glucan. Mannogalactan predominated in the cold water extract, and beta-d-glucan was the main product of the hot water extract. The hot water soluble fraction was further separated by preparative anion exchange chromatography into three sub-fractions; two of them were identified as branched beta-d-glucans with a structure similar to the corresponding polysaccharide of the original fraction. The alkaline extract contained a linear (1 -> 3)-alpha-d-glucan and a weakly branched (1 -> 3)-beta-d-glucan having terminal beta-d-glucosyl residues attached to O-6 of the backbone. The insoluble part after all extractions was identified as a polysaccharide complex containing chitin and beta-d-glucans.

Automated summary

This study focused on the isolation and structural characterization of polysaccharides from a basidiocarp of polypore fungus Ganoderma resinaceum. Different extraction methods were used to obtain polysaccharide fractions, and their purity, composition, and structure were characterized using various analysis techniques. The main polysaccharides identified were branched O-2-beta-d-mannosyl-(1 -> 6)-alpha-d-galactan and highly branched (1 -> 3)(1 -> 4)(1 -> 6)-beta-d-glucan in the cold water and hot water extracts, respectively.