Optimization of extraction process from Anemarrhena asphodeloides Bge. polysaccharide and its purification, structural characterization, and immunomodulatory activity

• The models of RSM and ANN were established. • A novel polysaccharide (AABPs-1-SG) was obtained from Anemarrhena asphodeloides Bge. • The structure of the new AABPs-1-SG was analyzed and deduced. • AABPs-1-SG showed good immunomodulatory activity. . The microwave-assisted aqueous two-phase extraction (MATPE) process of polysaccharides from Anemarrhena asphodeloides Bge. polysaccharides (AABPs) was optimized by genetic algorithm coupled with artificial neural network. A major polysaccharide fraction (AABPs-1-SG) was purified from the crude AABPs via DEAE-52 and Sephadex-G100 column chromatography, and AABPs-1-SG was investigated based on physicochemical properties, monosaccharide composition, molecular weight, structures characteristics, and immunomodulatory activity. The results show that the optimum extraction conditions to achieve the highest AABPs yield (9.42 ± 0.26)% was obtained at the microwave power of 333 W, ammonium sulfate mass fraction of 20%, ethanol concentration of 34%, and liquid-to-solid ratio of 15 mL/g. AABPs-1-SG with Mw of 5.39 kDa consisted of Fuc (0.98%), Fru (69.65%), Rha (0.84%), Ara (4.70%), Gal (6.33%), Glc (12.52%), Xyl (0.18%), and Man (1.37%), and Methylation analysis indicate that AABPs-1-SG was mainly composed of ten types of glycosidic linkages (T-Araf, 2,6-Fruf, 1,2-Araf, T-Glcp, 1,2,5-Araf, 1,2-Manp, 1,4-Galp, 1,4-Glcp, 1,6-Glcp, 1,3-Galp, 1,3,6-Glcp, and 1,3,6-Galp). Moreover, AABPs-1-SG has a triple helix structure, exhibited sheet-like, rod-like, and porous structures, and showed good thermal stability. Furthermore, AABPs-1-SG exhibited a strong immunomodulatory activity. The results provide important references for the development and utilization of AABPs.