Anti-inflammatory and analgesic properties in a rodent model of a (1→3),(1→6)-linked β-glucan isolated from Pleurotus pulmonarius

A glucan was extracted with hot water from the basidiomycete Pleurotus pulmonarius and shown to have a (1→3)-linked β-d-glucopyranosyl main-chain substituted at O-6 of every third unit by single β-d-glucopyranosyl non-reducing end units. This was shown by mono- and bidimensional nuclear magnetic resonance (NMR) spectroscopy, methylation analysis, and a controlled Smith degradation. The glucan was tested for its effects on the acetic acid-induced writhing reaction in mice, a typical model for quantifying inflammatory pain. It caused a marked and dose-dependent anti-inflammatory response, demonstrated by the inhibition of leukocyte migration to injured tissues (82 ± 6%) with an ID50 of 1.19 (0.74–1.92) mg/kg. Furthermore, animals previously treated with the glucan (3 mg/kg i.p.), showed a reduction of 85 ± 5% of writhes, after receiving the acetic acid injection. Furthermore, in the formalin test, the glucan (3–30 mg/kg, i.p.) also caused significant inhibition of both the early (neurogenic pain) and the late phases (inflammatory pain) of formalin-induced licking. However, it was more potent and effective in relation to the late phase of the formalin test, with mean ID50 values for the neurogenic and the inflammatory phases of > 30 and 12.9 (6.7–24.6) mg/kg and the inhibitions observed were 43 ± 5% and 96 ± 4%, respectively. These data showed that the glucan had potent anti-inflammatory and analgesic (antinociceptive) activities, possibly by the inhibition of pro-inflammatory cytokines.