桑叶多糖MLPⅡ的基本结构及对糖尿病模型大鼠的降血糖作用

The Preliminary Structure of Polysaccharide MLPⅡ from Mulberry Leaves and Its Hypoglycemic Effect on Rat Model of Diabetes

从桑叶中分离纯化获得一种具有降血糖活性的均一多糖组分MLPⅡ。高效液相色谱分析桑叶多糖MLPⅡ主要由甘露糖(man)、鼠李糖(rha)、葡萄糖(glc)、木糖(xyl)和阿拉伯糖(ara)等5种单糖组成,其摩尔比为n(man)∶n(rha)∶n(glc)∶n(xyl)∶n(ara)=8.73∶1.04∶6.53∶2.13∶1.00;红外光谱显示桑叶多糖MLPⅡ的主要连接键为β-糖苷键。桑叶多糖MLPⅡ对糖尿病模型大鼠的降血糖试验结果表明,150 mg/kg MLPⅡ治疗组糖尿病模型大鼠的体质量与对照组糖尿病模型大鼠相比提高了26.22%,而空腹血糖(FBG)浓度降低了52.89%,达到极显著水平,并且治疗组糖尿病模型大鼠的糖化血红蛋白(HbA1c)、空腹胰岛素(FINS)和C-肽(C-P)水平得到改善,损伤胰岛细胞得到修复,胰岛β细胞合成和胰岛素分泌的能力增强。研究结果提示,桑叶多糖MLPⅡ可有效控制糖尿病模型大鼠的体质量和空腹血糖水平,并改善糖耐量,而促进糖尿病模型大鼠胰岛β细胞合成及胰岛素分泌可能是桑叶多糖MLPⅡ降血糖作用机制之一。

MLPⅡ,the purified polysaccharide ingredient isolated from mulberry（Morus L.） leaves,possesses hypoglycemic activity.High performance liquid chromatography analysis showed that mulberry leaf polysaccharide MLPⅡ was mainly composed of mannose（man）,rhamnose（rha）,glucose（glc）,xylose（xyl） and arabinose（ara） with the molar proportion of 8.73 ∶1.04 ∶6.53 ∶2.13 ∶1.00.Infrared spectrometry analysis showed that polysaccharide MLPⅡ was mainly linked by β-glycosidic bond.The experimental results of hypoglycemic effect of polysaccharide MLPⅡ on diabetic rats indicated that,compared with the diabetic control group,body weight of diabetic rats in the 150 mg/kg MLPⅡ-treated group increased by 26.22%,while fasting blood glucose（FBG） decreased 52.89%,both of which reached extremely significant level.In addition,improvement on levels of glycosylated haemoglobin（HbA1c）,fasting insulin（FINS）,and C-peptide（C-P） were observed in the MLPⅡ-treated diabetic rats.The damage of pancreatic cells were repaired,and the insulin synthesis and secretion in pancreatic β-cells were enhanced following treatment with mulberry leaf polysaccharide MLPⅡ.These results suggest that mulberry leaf polysaccharide MLPⅡ could effectively control the levels of body weight and FBG levels,and ameliorate the glucose tolerance of diabetic rats.Moreover,mulberry leaf polysaccharide MLPⅡ exerts the antihypergly-cemic action at least in part by promoting insulin synthesis and secretion in diabetic rats.