Ultrasound-assisted extraction and purification of polysaccharides from Selaginella tamariscina: Structural...

In this study, ultrasonic-assisted extraction was employed to obtain polysaccharides from Selaginella tamariscina, and the extraction process was systematically optimized. The optimal conditions were determined to be a liquid-to-solid ratio of 23:1 mL/g, ultrasonic power of 280 W, extraction temperature of 60 °C, and an extraction time of 40 min, resulting in a polysaccharide yield of 2.02 %. Following purification, a novel neutral polysaccharide (STNP) was isolated, exhibiting a polysaccharide content of 87.47 % and a molecular weight of 35.324 kDa. The monosaccharide composition of STNP comprises galactose, glucose, mannose, arabinose, xylose, rhamnose, and trehalose in molar ratios of 30.62:24.49:17.75:12.45:5.38:4.93:4.37, respectively. STNP is a porous, amorphous polymer with a complex branched and cross-linked structure. Its main chain predominantly consists of 1,6-Gal(p), 1,3-Gal(p), 1,4-Gal(p), 1,4-Man(p), 1,6-Man(p), 1,3-Glc(p), 1,2-Glc(p), and 1,4-Glc(p), featuring multiple branches at the O-3 and O-4 positions. STNP exhibits diverse biological activities. In vitro antioxidant assays demonstrate a 96.60 % scavenging rate against ABTS radicals, a 74.22 % inhibition rate of nitrosamine synthesis, and significant protective effects against H₂O₂-induced oxidative damage in HepG2 cells. In terms of antihyperlipidemic activity, STNP inhibits porcine pancreatic lipase by 51.03 % and binds sodium glycocholate and sodium taurocholate at rates of 48.32 % and 40.98 %, respectively. Regarding antihyperglycemic effects, STNP inhibits α-glucosidase and α-amylase by 53.7 % and 52.39 %, respectively. Furthermore, in vitro antitumor experiments reveal that STNP exhibits notable inhibitory effects on A549 cells. These findings highlight the potential of STNP for applications in healthcare and drug development.