Study On Extraction, Purification And Lipid-lowering Related Activity Of Old Stem Polysaccharide From Asparagus Officinalis L.

Asparagus officinalis L. is a kind of valuable vegetable, which is widely planted in China. A large number of old stems are discarded during the commercialization process, which is not only a waste of the resource, reducing economic benefit, but also pollutes the environment. In order to achieve sustainable development and depth use of the old stems, which contain large amount of polysaccharides. Orthogonal test L9(34) was applied to investigate the factors of extraction temperature, time, material-water ratio and extraction time on the polysaccharides from residue of Asparagus (PRA). The PRA was then purified with three kinds of enzymes to explore the optimal conditions and effectiveness of removing proteins. Results showed that the optimum conditions for extraction were:100℃,3h of extraction time, solid/liquid ratio of1:20and1time of extraction. The yield of polysaccharides was (8.50±1.07)%and purity reached to (52.40±0.47)%after purification by Alkali Protease at the condition of50℃,1.5h of extraction time and0.5mg/mL of enzyme concentration.PRA’s mono-saccharide composition was analyzed by capillary zone electrophoresis, PRA consists of Galactose, Arabinose, Xylose, Glucose and Rhamnose mainly. PRA was then purified by column chromatography on DEAE-Cellulose52, resulting one component. PRA’s structure was primarily studied by UV-Vis Spectrum, IR, periodic acid oxidation and Smith degration, enzymolysis and so on. The results showed that there existed glycosidic bond, their linkage ways were1â†'6,1â†'2or1â†'4, and PRA is a kind of P-D-Pyranoid polysaccharide.The acute toxicity test was conducted to evaluate the safety of PRA. Four groups of mice were administrated with PRA one or several times within12hours and the doses were8.575g/kg,12.25g/kg,17.5g/kg and25g/kg respectively. Their survival status had been observed for2weeks. There were no obvious abnormal activities and symptoms of poisoning except the decreasing activities and food intake of mice on day1after administration. All mice were survived until the end of test. The mice were dissected after the test and no obvious lesions and anomalies were found, indicating that the safety dose of PRA is above25g/kg. The biological activities of polysaccharides to scavenge free radical, inhibit erythrocyte hemolysis and swelling of liver mitochondrion were also studied. The experiments of antioxidant proved that PRA could decrease the free radical of DPPH,·OH and O2·when its concentration is between0.125mg/mL and16mg/mL. It also had inhibitory effect on erythrocyte hemolysis and swelling of liver mitochondrion. The carbon particle clearance experiment found that compared with HFD control group, the clearance index and phagocytic index of low, medium and high dose group were significantly higher, while the thymus index and spleen index were not significant.For making clear mechanism of the results, we made in-depth studies. This research also investigated the effect of PRA on the lipid metabolism in high-fat diet (HFD)-induced hyperlipidemic mice.PRA group mice were administrated orally with PRA at dose of200mg/kg,400mg/kg and800mg/kg per day for8weeks. Positive control group was given20mg/kg of Simvastatin. The results showed that PRA could cause significant reduction in body weight increase. It was also appeared that PRA could decrease serum cholesterol and low density lipoprotein cholesterol(LDL-C) level, which further lower the Atherosclerosis Index(AI).These results indicated that PRA had a good regulation on lipid metabolism of high fat diet mice. PRA of400mg/kg and800mg/kg could decrease the AST, ALT and ALP level significantly, showing a protective effect on hepatic function. PRA of400mg/kg could significantly increased hepatic SOD activity. PRA of200mg/kg could significantly increased hepatic T-AOC, GSH and GSH-PX activities, suggesting that PRA maybe enhance the activities of antioxidant protective enzymes to alleviate the oxidative damage of hyperlipidemia mice. Semi-quantitative RT-PCR showed that PRA increased the mRNA expressions of PPAR-a, which further regulate fatty acid uptake genes, transport and metabolism genes, and other target genes during the process of lipid metabolism.Due to the above results, PRA has strong effects on free radical scavenging, relieving the red blood cell hemolysis and mitochondrial swelling. It also has the role of enhancing immune function and therapeutic effect on hyperlipidemic mice.