Extraction, structural analysis and antioxidant activity of aloe polysaccharide

Using fresh aloe as a raw material, aloe polysaccharide was prepared by the water extraction. After protein removal by sevage method, the aloe polysaccharide was refined by dialysis. The aloe polysaccharide was separated by diethylaminoethyl-52 (DEAE-52) cellulose column and Sephadex G-100 to obtain a single component of aloe polysaccharide. The molecular weight and monosaccharide components were determined by size exclusion chromatography-multi-angle laser light scatterer-differential refractive index detector (SEC-MALLS-RI) and high performance liquid chromatography (HPLC), respectively, and the structure was confirmed by nuclear magnetic resonance (NMR) spectrum. The molecular weight of aloe polysaccharide was 1.32 × 106 Da. The monosaccharide components were fucose (Fuc), arabinose (Ara), rhamnose (Rha), galactose (Gal), glucose (Glc), xylose (Xyl), mannose (Man), galacturonic acid (Gal-UA) and glucuronic acid (Gul-UA), and the proportions of each component were 0.37%, 7.52%, 3.46%, 10.23%, 26.99%, 1.61%, 35.02%, 14.25% and 0.55%, respectively. In order to obtain the structure-activity relationship (SAR) of aloe polysaccharide, the derivatives, including acetylated aloe polysaccharides (AAP), phosphorylated aloe polysaccharides (PAP) and carboxylated aloe polysaccharides (CAP) were synthesized. Results of antioxidant test in vitro showed that aloe polysaccharide and its derivatives had a good activity.