To prepare non-starch polysaccharides from Yangshan Dioscorea opposita Thunb. by ultrasonic-assisted water extraction, and investigate their antioxidant activities.

Hot-water extraction and ultrasonic-assisted hot-water extraction combined with glucoamylase were adopted to obtain Dioscorea opposita Thunb.non-starch polysaccharides, designated as CYP-H and CYP-U, respectively. The content of total sugar, uronic acid and protein of the 2 kinds of polysaccharides were determined by chemical assays. Size-exclusion chromatography coupled with multi-angle laser light scattering, Fourier-transform infrared spectroscopy and ion chromatography were used to characterize their structural features including molecular-weight distribution, infrared absorption and monosaccharide composition. The antioxidant activities of the 2 kinds of polysaccharides were compared via multiple chemical models including 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical, hydroxyl radical, 2,2’-azinobis-(3-ethylbenzthiazoline-6-sulphonate) (ABTS) cation radical and Fe³⁺ reduction assay, as well as the zebrafish oxidative-stress model induced by 2,2’-azobis(2-amidinopropane) dihydrochloride (AAPH).

The yields of CYP-H and CYP-U were 17.72% and 19.53%, respectively, with the total sugar, uronic acid and protein content of 77.56%, 19.51%, 2.29%, and 82.56%, 20.67%, 4.46%, respectively. Their weight-average molecular weights were 5.263 kDa and 6.645 kDa, respectively, and both exhibited typical infrared absorption spectra characteristics of polysaccharides. Ion chromatography analysis revealed that both CYP-H and CYP-U contained arabinose, galactose, glucose and mannose. The molar ratios were 1.0:6.8:93.5:11.1 for CYP-H and 1.0:4.8:185.2:13.1 for CYP-U. These results demonstrated the differences in the chemical composition and molecular structural characteristics of the 2 kinds of non-starch polysaccharides. Moreover, within the range of 2–10 mg/mL, both polysaccharides exhibited scavenging activity against DPPH radicals, hydroxyl radicals and ABTS⁺ radicals, as well as Fe³⁺ reduction capacity. However, CYP-H and CYP-U exhibited differences in their ability to scavenge different free radicals. Moreover, both CYP-H and CYP-U reduced reactive oxygen species (ROS) and malondialdehyde (MDA)levels while enhancing superoxide dismutase (SOD) activities in the AAPH-induced oxidative stress zebrafish model, with CYP-U demonstrating superior efficacy compared to CYP-H and exhibiting a favorable dose-response relationship.

Ultrasonic assistance enhances the yield of non-starch polysaccharides from Yangjiang Dioscorea opposita Thunb. and modestly increases their antioxidant activity in vivo. These findings provide scientific support for the applications of Yangjiang Dioscorea opposita Thunb. in functional foods with antioxidant potential.