Isolation, purification, characterization, and antioxidant activity of low-molecular-weight polysaccharides from Sparassis latifolia

Six polysaccharides (SF-FB11, SF-HW21, SF-CA31, SF-HA41, SF-FF51, and SF-FR61) of similar molecular weights (MW) (30-50 kDa) were extracted from the fermentation liquor, mycelia, and basidiomata of Sparassis latifolia by different methods. Structural analyses of these purified polysaccharides indicated that they were all branched, with a degree of branching (DB) ranging from 0.2 to 0.4. The polysaccharides exhibited strong scavenging activities for 2,2‑diphenyl‑1‑picrylhydrazyl and hydroxyl radicals. Their antioxidant activities were correlated to some extent with their composition but significantly with the DB. The polysaccharides with a low 1,3‑d‑glucose content and glucose: galactose ratio, or a low DB (0.2-0.3) had higher antioxidant activities. Additionally, the correlation between the extraction yield and antioxidant activities of the polysaccharides was assessed. The low-MW polysaccharides extracted by alkali treatments had both high yield and antioxidant activities. Additionally, both the yield and antioxidant activities were found to be influenced by the size, extraction method, and source (fermentation liquor, mycelia, or basidiomata) of the polysaccharides. These results indicate that polysaccharides isolated from S. latifolia have strong antioxidant activities closely associated with the polysaccharide structure and extraction method, thus providing a scientific basis for further use of these polysaccharides.