Structure characterization of one polysaccharide from Lepidium meyenii Walp., and its antioxidant activity and protective effect against H2O2-induced injury RAW264.7 cells

The structural characterization, antioxidant activity and protective effect against H2O2-induced injury RAW264.7 cells of a new polysaccharide (MP1) isolated from Lepidium meyenii Walp. were investigated. The molecular weight was estimated to be 4.67 × 105 Da by HPLC-ELSD analysis. Monosaccharide composition was determined to be arabinose and galactose in a molar ratio of 2:1 by GC-MS and PMP-HPLC-UV analysis. Methylation combined with 1D and 2D NMR spectrum analysis revealed that MP1 was an arabinogalactan. MP1 possessed a moderate antioxidant activity in vitro in DPPH, ABTS, superoxide and hydroxyl radicals scavenging, Fe2+ chelating, lipid peroxidation inhibition and reducing power assays. MP1 could also effectively protect RAW264.7 cells from H2O2-induced injury by maintaining stable cell viability, decreasing ROS, MDA and LDH level and enhancing SOD, GSH-Px and CAT activity. These results suggested the potential utilization of MP1 as a natural antioxidant for food and pharmaceutical applications.