Ultrasonic disruption extraction, characterization and bioactivities of polysaccharides from wild Armillaria mellea

An efficient ultrasonic disruption extraction (UDE) of polysaccharides from Armillaria mellea (AM) were optimized by response surface methodology (RSM). Under optimum conditions: ultrasonic power 915.00 W, temperature 69.27 °C and time 39.13 min, the crude polysaccharides (AMPs) yield was 19.5%. Two purified fractions AMPs-1-1 and AMPs-2-1 were obtained through anion-exchange and gel chromatography. AMPs-1-1 was a heteropolysaccharide with average molecular weights of 1.23 × 105 Da, and composed of Glc, Gal and GlcA with mole percentages of 89.06%, 9.59% and 1.34%, respectively, owning a backbone structure of (1→)-β-d-Glcp, (1 → 3,6)-α-d-Glcp and (1 → 3)-β-d-Glcp residues. AMPs-2-1 was a heteropolysaccharide with average molecular weights of 6.76 × 104 Da, and composed of Glc, Gal, GlcA and Man with mole percentages of 65.28%, 22.87%, 2.87% and 8.98%, containing a main backbone chain of (1 → 3,6)-α-d-Glcp and (1 → 6)-β-d-Glcp residues. AMPs-2-1 possessed obviously antioxidant activities in terms of stronger scavenging activity against DPPH· and ABTS+⋅, higher FRAP and ORAC value than AMPs-1-1. AMPs-2-1 could promote splenocyte lymphocytes and RAW264.7 macrophages proliferation and enhanced the phagocytosis of macrophages, exhibited significant immunomodulatory activities. These results suggested that UDE is an effective extract technology, and AMPs-2-1 could be explored as potential natural antioxidants and immunomodulatory agents.