Exopolysaccharide produced by Pleurotus sajor-caju: its chemical structure and anti-inflammatory activity

Edible mushrooms are high nutritional value foods, which contain proteins, fibers, minerals, vitamins, and carbohydrates. Among their carbohydrates are some polysaccharides with recognized therapeutic effects. It was reported in this manuscript the structural characterization and antinociceptive and anti-inflammatory activities of an exopolysaccharide (EPS) produced by Pleurotus sajor-caju. The purified EPS was a mannogalactan (PEIsR), which was composed by mannose (37.0%), galactose (39.7%), and 3-O-methyl-galactose (23.3%). The polysaccharide was purified by freeze-thawing and dialysis, and it was characterized by GC-MS analysis and NMR spectroscopy. The mannogalactan is constituted by a main chain of (1 → 6)-linked α-D-Galp and 3-O-methyl-α-D-Galp units. Some of the α-D-Galp units were substituted at O-2 by non-reducing end units of β-D-Manp. According to the literature review conducted, this is the first time that a methylated polysaccharide was observed on EPS of P. sajor-caju. The mannogalactan was able to reduce the nociception, in vivo, in the writhing and formalin tests and also reduced the carrageenan-induced paw edema, which indicates that it could be an effective antinociceptive and anti-inflammatory agent.