Structural characterization and DPPH radical scavenging activity of a polysaccharide from Guara fruits

摘要

The crude polysaccharides were extracted from fruits of Psidiumguajava Linn, by hot water. After removal of proteins, isolation and purification by DEAE-52 Cellulose chromatography and Sephadex G-75 gel filtration, a polysaccharide (GP70-2) was obtained and structurally characterized. GP70-2 has a relative molecular weight of 74 kDa and was composed of D-galactose and L-arabinose in the ratio of 1:1, with a specific optical rotation of [a]_D~(25) = +101°. Structural characterization of this novel polysaccharide was carried out using infrared spectroscopy, methylation analyses, and NMR studies (~1H, ~(13)C,~1H-~1H-COSY, HMQC, and HMBC). Based on the above data, This polysaccharide showed a concentration dependent DPPH- radical scavenging activity.