Abstract:The crude polysaccharide of Ostericum sieboldii (WOSP) was extracted, separated and purified to obtain acidic polysaccharide (WOSP-A) and neutral polysaccharide (WOSP-N). The basic chemical properties, basic structural characteristics of the sugar chains, and in vitro antioxidant activities of different polysaccharide components were analyzed. Results showed that the yield of WOSP obtained by water extraction and alcohol precipitation was 6.78%, and the yields of WOSP-A and WOSP-N obtained via separation by ion exchange chromatography were 51.34% and 2.55%, respectively. Monosaccharide composition analysis showed that WOSP was a heteropolysaccharide mainly composed of GalA (11.36%), Gal (41.50%) and Ara (38.08%). Based on both the infrared spectroscopy results and enzymatic hydrolysis results, it was speculated that WOSP-A was a pectin composed of homogalacturonan (HG) and type I arabic galactans (AG-I) domains containing mainly GalA (46.99%), Gal (26.56%) and Ara (19.94%), whilst WOSP-N was a pectin composed of type II arabic galactans (AG-II) domains containing mainly Gal (55.32%) and Ara (30.69%). The comparison of the antioxidant activities of the three polysaccharides from O. sieboldii revealed that the antioxidant activity of WOSP was higher than those of WOSP-A and WOSP-N, and WOSP had higher scavenging abilities for DPPH· and O2-·, (which could reach 96.42% and 86.70% at a polysaccharide concentration of 10 mg/mL). In conclusion, WOSP, WOSP-A and WOSP-N from O. sieboldii all had O-H and C-H functional groups, and possessed certain in vitro antioxidant activities. This study will provide a theoretical reference for the development and utilization of wild vegetables in the Northeast China.