Structural characteristics and antioxidant activities of a novel polysaccharide from Euphorbia himalayensis root

Euphorbia himalayensis Boiss. is an alpine member of the Euphorbiaceae family. Its dried roots have been used to treat digestive problems and chest congestion in traditional Tibetan and Mongolian medicine. Despite thousands of years of use in medicine, the bioactive compounds of the root remain unknown. Herein, we isolated a novel aqueous-soluble polysaccharide (EHP2) from the E. himalayensis root and determined its structural characteristics via high-performance gel permeation chromatography, Fourier-transform infrared spectroscopy, gas chromatography-mass spectrometry, and nuclear magnetic resonance spectrometry. The homogeneous molecular weight of EHP2 was 23.6 kDa with narrow polydisperity (Mw/Mn = 1.4), and EHP2 mainly comprised of glucose (86.4%), galactose (11.9%) and mannose (1.7%). The major backbone of EHP2 was →4)-α-D-GalAp-(1 → 4)-α-D-Glcp-(1 → and the branch chain was α-D-Glcp-(1→. The antioxidant activity of the EHP2 was evaluated by 1,1-diphenyl-2-picrylhydrazyl (DPPH) and superoxide anion radical scavenging assays, and antioxidant enzyme activity (SOD, GSH and MDA) was determined in human umbilical vein endothelial cells (HUVECs). The EHP2 demonstrated lower potential scavenging effects on DPPH and superoxide free radical scavenger than ascorbic acid, and in HUVECs, it led to increased SOD and GSH activities and decreased MDA levels. This study is the first to describe an E. himalayensis polysaccharide compound with potential antioxidant activity.