Structural characterisation of a novel bioactive polysaccharide from Ganoderma atrum

The structure of a novel bioactive polysaccharide fraction from Ganoderma atrum (PSG-1) was characterised by methylation analysis and 1D/2D nuclear magnetic resonance (NMR) spectroscopy. Sugar analysis revealed that PSG-1 was composed of glucose (Glc), mannose (Man), galactose (Gal) and galacturonic acid (GalA) in molar ratio of 4.91:1:1.28:0.71. Methylation and GC–MS analysis indicated that the main linkage type was 1,3-linked-Glcp (21.08%), followed by T-Glcp (18.68%), 1,3,6-Glcp (12.97%), 1,4-Galp (12.70%), 1,6-Glcp (12.33%), 1,2-Manp (8.06%), 1,4-GalpA (6.15%), 1,4-Manp (4.55%) and 1,4,6-Glcp (3.24%). Combined the methylation analysis results with 1D (1H, 13C) and 2D (DQF-COSY, TOCSY, HSQC and HMBC) NMR spectroscopy, a preliminary structure of PSG-1 was proposed as follows:Figure optionsDownload as PowerPoint slide

► A novel polysaccharide from Ganoderma atrum (PSG-1) was extracted and purified.
► Structure of PSG-1 was reported by using methylation and NMR spectroscopy.
► PSG-1 was mainly composed of Glc, Gal, Man and GalA (4.91:1:1.28:0.71).
► PSG-1 was a heteropolysaccharide comprised a backbone of 1,3- and 1,6-Glcp branched at O-3 and O-6 position.