Ultrasound-assisted enzyme extraction, primary structures and bioactivities of Selaginella uncinata polysaccharides

In this study, polysaccharides (SUP) were extracted from Selaginella uncinata using ultrasonic-assisted enzymatic extraction (UAEE) and decoction method extraction (DME). UAEE was optimized by response surface methodology, with optimal conditions of 40 min extraction time, a 40:1 liquid-to-material ratio, cellulase to pectinase ratio of 2:1, and pH 5.0. Under these conditions, the extraction rate (2.08 ± 0.26 %) and polysaccharide content (58.78 ± 0.31 %) of UAEE-SUP were significantly higher than DME-SUP (1.63 ± 0.30 % and 38.50 ± 0.22 %, respectively). Structural analysis revealed that UAEE-SUP primarily contained Man, Glc, Gal, Xyl, and Ara, with a molar ratio of 6.96:67.48:13.08:2.50:5.61, and a molecular weight of 55,897 Da, while DME-SUP was composed of Man, Rha, GalA, Glc, Gal, Xyl, and Ara, with a molar ratio of 11.93:4.98:11.21:13.47:26.71:5.15:22.89, and a molecular weight of 13,929 Da. Both polysaccharides exhibited α and β configurations. In vitro biological activity tests indicated that UAEE-SUP exhibited good lipid-lowering, nitrite scavenging, acetylcholinesterase inhibition, and anticancer activities. Notably, in terms of lipid-lowering effects, the pancreatic lipase inhibition rate of UAEE-SUP reached 70.34 ± 1.60 %, which was significantly higher than that of DME-SUP at 52.41 ± 1.12 %. This study provides a theoretical basis for the efficient extraction of SUP and its potential pharmaceutical applications.