Effects of Ultrasound-Assisted Treatment on Physicochemical Properties and Biological Activities of Polysaccharides from Sargassum

The aim of this study was to investigate the effect of ultrasonic treatment on the physicochemical properties and bioactivities of polysaccharides from <i>Sargassum</i> samples (SPs) extracted with different solvents. The alkali-assisted extraction of polysaccharide (SPA), acid-assisted extraction of polysaccharides from (SPB), and hot water extraction of polysaccharides (SPCs) were perofrmed on <i>Sargassum</i>. Ultrasonic treatment was performed with the SPA, SPB, and SPC in turn, and named USPA, USPB, and UPSC, respectively. The results showed that SPs mainly consisted of mannose, glucose, xylose, rhamnose, galactose, fucose, glucuronic acid, mannuronic acid and guluronic acid. The molecular weight of SPA (434.590 kDa) was the lowest under different solvent extractions, and the molecular weights of SPA, SPB, and SPC were reduced after sonication. SPA had a high carbohydrate content of (52.59 ± 5.16)%, and SPC possessed a high sulfate content of (3.90 ± 0.33)%. After ultrasonic treatment, the biological activities of SPs were significantly increased. The <i>α</i>-glucosidase inhibition assay reflected that the IC50 values of the ultrasonic treatment SPs were significantly reduced, and USPA showed the best activity, with an IC50 of (0.058 ± 0.05) mg/mL. Antioxidant assays demonstrated that USPC exhibited greater DPPH- and ABTS-scavenging capacity. In the anti-glycosylation assay, SPs after sonication demonstrated excellent inhibition of glycosylation products and protein oxidation products, with USPA showing the highest inhibition rate. In conclusion, the biological activities of SPs were enhanced after ultrasonic treatment. This study provides a theoretical reference for their use in food and medicines.