An alkali-extracted polysaccharide from Pleurotus eous and exploration of its antioxidant and immunomodulatory activities

The Pleurotus eous fruiting body was used to prepare an alkali-extracted polysaccharide (PEAP). The goal was to characterize PEAP’s physicochemical characteristics, structural characteristics, antioxidant capabilities, and immunological functions. PEAP had an average molecular weight of 156 kDa and was composed of glucose, galactose, rhamnose, xylose, and mannose. Both the FTIR and NMR spectra of PEAP showed distinctive polysaccharide bands. In addition to demonstrating significant scavenging activity against 2,2-azino-bis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS) (EC₅₀ = 16.06 mg/mL), superoxide radicals (EC₅₀ = 9.77 mg/mL), and 1,1-diphenyl-2-picrylhydrazyl radicals (DPPH) (EC₅₀ = 16.21 mg/mL), PEAP also exhibited reducing power (EC₅₀ = 9.71 mg/mL), chelating ability (EC₅₀ = 7.89 mg/mL), and inhibition of β-carotene bleaching (EC₅₀ = 2.06 mg/mL). PEAP was revealed to have an immunomodulatory effect as it increased the proliferative and phagocytic activity of RAW264.7 cells and caused concentration-dependent releases of nitric oxide (NO), interleukin 4 (IL-4), interleukin 12 (IL-12), interleukin 17 (IL-17), tumor necrosis factor (TNF-α), and interferon-gamma (IFN-γ) by macrophages. The results showed that PEAP might be a natural immunostimulant and antioxidant in functional foods or medicine.