Chemical structure and antioxidant activity of a neutral polysaccharide from Asteris Radix et Rhizoma

Asteris Radix et Rhizoma (AR) has been widely used as a herbal medicine for treating various symptoms and possesses a number of bioactivities. A neutral polysaccharide ARP-1 was isolated from AR with weight-average molecular weight of 214 kDa. The heteropolysaccharide ARP-1 was composed of fucose, arabinose, galactose, glucose and mannose with a molar ratio of 0.40:14.25:10.22:1.06:0.41. Linkage and NMR analysis showed that ARP-1 had a backbone containing →3,6)-β-d-Galp-(1→ and →6)-β-d-Galp-(1 → residues, and oligosaccharide side chains containing Araf and Galp units were attached to the backbone at C-3 of →3,6)-β-d-Galp-(1 → residues. Antioxidant activity assays showed that ARP-1 exhibited potent antioxidant activities, including ABTS, hydroxy and DPPH radicals scavenging and reducing power. Besides, ARP-1 decreased the production of ROS and MDA, and improved the activities of SOD, which resulted in the protection of PC12 cells against H₂O₂-induced oxidative stress. The findings indicated that ARP-1 might be used as a potential natural antioxidant.