Study On Isolation, Purification And Properties Of Rapeseed Polysaccharides

Crude polysaccharides (PRM) were extracted and purified from cold pressing rapeseed meal used as material. The technics that co-produced protein and polysaccharides from rapseseed meal mainly by ways of low alkali extraction and in series ultrafiltration was researched. Two fractions were separated from PRM with DEAE-cellulose and their chemical constitutes and molecular characteristics were also analyzed. The immune and in vivo antioxidant activities of PRM were also studied. The in vitro antioxidant activities and mechanisms of the two fractions were further investigated. It may provide theoretical guides for industrialization and application of rapeseed meal polysaccharides.The extraction of PRM, separations of single fractions of the polysaccharides, chemical constitutes and molecular characteristics of single fractions of the polysaccharides were studied. The defatted rapeseed meal was extracted with 0.3% NaOH aqueous solution. Then, the solution was filter through a metal sift to remove the big particles. The solution was added Sevage reagent (chloroform: 1-butanol, 4:1) to remove protein and the resultant supernatant was in turn dialyzed, concentrated and precipited with 95% EtOH. The precipitate collected by centrifugation was washed successively with absolute ethanol, acetone and ether, and crude polysaccharides, named as PRM, were obtained. PRM were further separated with a DEAE-Cellulose -52 column and the column was in turn eluted with water and 0.05M NaCl aqueous solution. Two fractions were got. After concentration, the two fractions were in turn dialyzed and lyophilized. Their in vitro antioxidantant capacities were also evaluated. Furthermore, their constitutes were analyzed. Neutral sugar, sulfate, protein and uronic acid contents, amino acid constitutions and molecular weights of the fractions were analysed. Monosaccharides that constituted the fractions were tested by GC-MS. Besides, their helix configures were analyzed in the Congo red test.Manufacturing crude polysaccharides from rapeseed meal on pilot scale was studied. The effects of extraction, grind and membrane separation conditions on yields and purities of the rapeseed meal polysaccharides were studied. The optimum extraction, grind and membrane separation conditions were chosen. The molecular weight ranges and distributions of the polysaccharides were also analyzed with HPLC.The immunostimulating properties of PRM were investigated using various in vivo and vitro tests. Mice used as trial animals were divided into normal group, low dosage group, middle dosage group and high dosage group. The crude polysaccharides were administered to test animals using vehicle solution (physiological saline) via a gastric gavage. Thirty days later, the immunostimulating indexes of the mice were evaluated. The results shows the hymic, splenetic and phagocytic indexes of the mice administered with PRM were increased. The delayed-type hypersensitivity(DTH) against SRBC, proliferation of spleen cell in mice and macrophage cellin mice's abdominal cavities and formulation of haemolytic plaque and serum haemolysin in the mice administered with PRM were remarkably promoted as compared with control group. Collectively, PRM showed good immunostimulating properties.In vivo antioxidant capacities of the crude polysaccharides from rapeseed meal (PRM) were also studied. The polysaccharides, vitamin C, and vitamin E (α-tocopherol) were respectively administered to test animals using vehicle solution (physiological saline) via a gastric gavage. Vitamins C and E were used as positive controls. Thirty days later, the in vivo antioxidative capacities of the mice were evaluated using different indexes, including glutathione peroxidase (GSH-Px), catalase (CAT) and superoxide dismutase (SOD), total antioxidant capacity (T-AOC) and malondialdehyde (MDA) in the serum, live, heart and small intestine. These antioxidant indexes were also compared with those of standard antioxidants (vitamin C andα-tocopherol). The results indicated that PRM markedly increased the activities of GSH-Px, CAT and SOD, and T-AOC levels and decreased MDA levels. The findings suggest that PRM have strong in vivo antioxidant capacities and may be recommended as health food in the future.In vitro antioxidant activities of the two fractions were determined, including scavenging activity toward superoxide anion radicals, hydroxyl radicals and nitric oxide radicals, reducing power and inhibitory effects against the microsomal lipid peroxidation, compared to that of ascorbic acid. The results indicated that the two fractions exhibited not only good reducing power and inhibitory effects on the microsomal lipid peroxidation, but also strong scavenging activity toward superoxide anion radicals, nitric oxide radicals and hydroxyl radicals. In addition, positive correlations were also observed between the superoxide anion radical-scavenging activity and the protein contents of the polysaccharides, and the reducing power and the sulfate contents. These findings thus clearly suggest the two fractions possess potent in vitro antioxidant activity.