茶多糖降糖活性中心AN蛋白组分的制备筛选及体内外降血糖实验研究

Identification and preparation of a glycol-protein fraction AN from tea extracts and its in vivo and in vitro anti-hyperglycosemia activity

该文比较了不同种类茶叶有效成分活性，筛选了最优茶叶种类及其降血糖活性中心组分，并研究其降血糖活性和可能的作用机制。对茶叶进行提取，用超滤技术将茶叶提取物E进行不同相对分子质量截留并富集；用α-葡萄糖苷酶体外实验模型对提取物进行筛选，用大鼠离体小肠囊翻转模型进一步验证有效组分活性。用四氧嘧啶诱导的sD大鼠糖尿病模型和高脂饮食合并链脲佐菌素诱导的大鼠糖尿病模型，研究上述活性组分对糖尿病大鼠血糖、体质量、胰岛素等的影响。实验结果表明，不同种类的茶叶提取物对α-前萄糖苷酶的抑制作用差异较大，茶叶提取物E对α-葡萄糖苷酶的抑制作用较强，茶叶提取物E的不同组分对α-葡萄糖苷酶的抑制作用也差异较大，其中FractionAN蛋白组分对α-葡萄糖苷酶的抑制作用较其他组分强，并且FraCtionAN蛋白组分对大鼠小肠囊葡萄糖转运有较强的抑制作用，能降低糖尿病大鼠的血糖值、保护胰岛素细胞。结果提示，AN蛋白组分为茶多糖的降血糖活性中心，对α-葡萄糖苷酶和小肠囊葡萄糖转运具有较强的抑制作用，对糖尿病大鼠有保护作用。

The present study compared active ingredients of tea from different sources to select tea type and the fraction of tea ex- tracts for the highest anti-hyperglycemic activity, and to verify anti-hyperglycemic activity of the selected tea extract. Tea extracts were separated and enriched by molecular weight using ultra-filtration technology. The extracts were first screened by α-glucosidase inhibi- tion assay, followed by using a rat inverted intestine sac system to measure the effect on glucose transport. Both alloxan-indueed diabet- ic rat model and high-fat diet combined with streptozotocin-induced rat diabetes mellitus model were used to study the effects of active components on blood glucose, body weight, insulin resistance. The experimental results showed that the different kinds of tea extracts had different inhibitory effects on α-glucosidase, and the inhibitory effect of tea extract E on α-glucosidase was stronger. The effects of different components of tea extract E also varied greatly, of which Fraction AN protein had stronger inhibitory effect on α-glucosidase than other fragments, and Fraction AN＇protein had a strong inhibitory effect on glucose transport, reduced blood sugar and normalized insulin secretion in diabetic rats. The results shggest that a glycol-protein fraction （AN） from the extracts might be responsible for the anti,hyperglycemic activity of tea polysaccharides. The AN glycol-protein fraction has strong inhibitory effects on both azglucosidase ac- tivity and glucose transport by the small intestine. It also reduced blood glucose level and normalized insulin secretion in diabetic rats, and has a protective effect on diabetic rats.