Studies On Quality Control And Anti-diabetic Activities Of Polysaccharides From Liriope Spicata Var. Prolifera

Liriope spicata var. prolifera, which is regarded as both functional food and medicine by the Chinese Ministry of Public Health, is massive cultivated in China’s Hubei province. It was recorded as ’SuizhouMaimendong’ in ’Zhenglei Bencao’, a medical classic in the Song Dynasty, and has been used in traditional Chinese medicine to treat diabetes for centuries. The hypoglycemic activity test showed that the crude polysaccharides derived from Liriope spicata var. prolifera could improve hyperglycemia and insulin resistance in low-dose-streptozotocin-induced diabetic mice. In a phytochemical investigation, we found that the total polysaccharides from Liriope spicata var. prolifera (TLSP) were mainly comprised of two fractions (LSP1and LSP2), which both have a backbone structure of-(1→2)-fructosyl residues that branch at O-6with fructosyl residues and terminate with a glucosyl residue and a fructosyl residue, and also have remarkable hypoglycemic activities. Hypoglycemic activities showed no differences among LSP1, LSP2and TLSP in a KKAy mouse model. Therefore, this article selected only TLSP as the research object.This study was consisted of four parts. The first part was about quality control of TLSP. The second part, we chose a rat model of diabetes to examine the hypoglycemic effects. In the third part, we explored the more clear mechanisms of TLSP. The last part was review on quality control and anti-diabetic activities of polysaccharides.The first part::In this study, the following five aspects were considered to ensure the quality of TLSP.(1) When the monosaccharide composition of TLSP was analyzed by TLC, TLSP should show same position and color spots with fructose and glucose standard.(2) HPGPC/ELSD method was used to detected the molecular weight of TLSP, which must be between3000and5000Da.(3) To determine the content of total sugar in TLSP, The content of total sugar in TLSP was determined by anthrone-sulfuric acid colorimetry method using fructose as standard sample. The content of total sugar in TLSP must be greater than or equal to95%.(4) Two HPLC methods were optimized and validated for quantification of monosaccharide composition in TLSP. The results shown the RP-HPLC/UVD method was a rapid, accurate and economic alternative for the qualitative and quantitative of monosaccharide composition in TLSP with high sensitivity and wide linear range. Fructose content of TLSP must be between98%and104%, and glucose content of TLSP must be between4%and6%.(5) HPGPC was used to examine small molecular weight impurity in TLSP, and UV scanning spectrum was used to examine proteins, peptides or amino acid impurity in TLSP.The second part:We used high-fat-fed and low-dose STZ-treated diabetic rats as a animal model to investigate the effects of TLSP on glucose metabolism. We found the HbAlc values and FBG levels of diabetic rats administered with TLSP were dramatically reduced. TLSP treatment showed a marked improvement in the oral glucose tolerance of diabetic rats, further demonstrated the hypoglycemic effects of TLSP. At the same time, we found that TLSP could reduce serum lipid and improve renal function parameters. The results of histological morphological analysis showed that TLSP could effectively inhibit the damage to liver and pancreas tissue in diabetic rats. These meant TLSP had preventive effect on complications of diabetes.The third part:(1) TLSP could inhibit GSK-30expression, while increasing InsR/IRS-1/PI3K/Akt/Glut4expression in liver tissue. These results indicate that TLSP had a positive effect on liver insulin-signaling transduction.(2) Administration of TLSP to diabetic rats resulted in significantly promoting the activity and mRNA levels of GK and GS, while depressing G6Pase and GP activity and mRNA levels in diabetic rats. In short, TLSP could improve liver glucose metabolism.(3) TLSP increased the enzyme activities (SOD, CAT and GSH-px), which are important antioxidant enzyme and scavenger of free radicals, and decreased the contents of MDA, which can reflect the degrees of the lipid peroxide of organism. All of these might be the reasons for the hypoglycemic effects of TLSP on diabetic rats.(4) Down-regulation the system of AGE-RAGE was included amongst the mechanisms of the preventive effects of TLSP on diabetes complications.The fourth part:This part summarized the quality control methods of polysaccharides and the reports on the anti-diabetic activity of polysaccharides between2009and2014. I hope there some help for research and development of anti-diabetic polysaccharides.