Preparation of a hydroxypropyl Ganoderma lucidum polysaccharide and its physicochemical properties

A hydroxypropyl Ganoderma lucidum polysaccharide (H-GLP) was prepared from a low-value water-insoluble polysaccharide from G. lucidum (GLP) using propylene oxide under an alkaline condition. The H-GLP was characterised for its chemical structure with IR and 13C NMR spectra and analysed for its mono-sugar composition, molecular weight, and hydroxypropyl content. H-GLP contained mannose, glucose, and galactose in a mole ratio of 1.0:36.5:3.59, respectively, with an average molecular weight of 788 kDa and a hydroxypropyl content of 12.05%. H-GLP also had an excellent water solubility of more than 50 mg/mL, suggesting that hydroxypropylation might serve as an effective approach to enhance water solubility of GLP. H-GLP was also compared to the original GLP and ascorbic acid for antioxidant properties. H-GLP showed much stronger free radical scavenging capacity against hydroxyl and superoxide anion radicals and hydrogen peroxide than GLP. These results suggested the potential of hydroxypropylation in developing water-soluble antioxidative polysaccharides from GLP to enhance the profitability of G. lucidum production and processing industries.