Structural elucidation, anti-radical and immunomodulatory activities of polysaccharides from the roots of Glehnia littoralis

This study investigated the structural elucidation, anti-radical and immunomodulatory activities of polysaccharides from the roots of Glehnia littoralis. A crude polysaccharide was extracted from the roots of G. littoralis through the ultrasonic-assisted extraction and further purified by DEAE-52 cellulose and Sephadex G-100 gel column, a major polysaccharide fraction named GLP80-1 was obtained. The chemical properties and structure of GLP and GLP80-1 were characterized by acid hydrolysis, methylation analysis, along with high performance gel permeation chromatography, Fourier transform infrared, nuclear magnetic resonance, scanning electron microscope, thermogravimetric analysis and X-ray diffraction. The molecular weight distributions of GLP were determined as 1.89 x 10(6) and 1.26 x 10(4) Da. The monosaccharide composition of GLP was glucose, glucuronic acid, galactose and arabinose with molar ratios of 0.91:0.04:0.03:0.02, respectively. The average molecular weight of GLP80-1 was determined as 1.63 x 10(4) Da. The structure of GLP80-1 was deduced to be a homogenous glucan, comprised a main chain of (1 -> 4)-linked-alpha-D-Glcp with a single alpha-D-Glcp branch substituted at C-6. The results of biological activities in vitro showed that GLP and GLP80-1 exhibited free radical scavenging effects, and displayed promotion for the proliferation of mouse spleen lymphocytes and RAW264.7 cells. The data indicated that GLP and GLP80-1 had the potential to be explored as novel natural antioxidant and immunomodulator for application in functional food.