Structural characterisation and antioxidant activity of Angelicae dahuricae radix polysaccharides

A refined polysaccharide component (ADP-0.1-1) was isolated and purified from Angelicae dahuricae radix. Structural analysis revealed that ADP-0.1-1 had a molecular weight of 1.32 × 10⁷ Da and was primarily composed of galactose (Gal), arabinose (Ara), galacturonic acid (GalA), rhamnose (Rha), mannose (Man), and glucose (Glc). Methylation analysis, along with nuclear magnetic resonance (NMR) spectroscopy, indicated that the main chain of ADP-0.1-1 was →3,5)-α-Araf-(1→ and →4,6)-β-D-Galp-(1→, the side chains were →4)-β-D-Glcp-(1→, →4)-α-GalAp-(1→, →5)-α-Araf-(1→, and terminal units were α-Araf-(1→ residues. In an H₂O₂-induced oxidative stress model using RAW264.7 macrophages, ADP-0.1-1 not only reduced malondialdehyde (MDA) content but also enhanced the activities of key antioxidant enzymes including superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), and catalase (CAT). Furthermore, it up-regulated the mRNA expression of antioxidant-related genes such as HO-1, NQO1, SOD2, GPX1, and CAT. The mechanism underlying these effects is closely associated with the activation of the Nrf2/HO-1 signalling pathway.