本实验通过高速逆流色谱从紫甘薯茎叶中制备分离得到绿原酸（1）、4,5-O-咖啡酰基奎宁酸（2，异绿原酸C）、3，5-O-咖啡酰基奎宁酸（3，异绿原酸A）及3,4-O-咖啡酰基奎宁酸（4，异绿原酸B）等四个高纯度天然化合物，并以4-硝基酚-α-D-吡喃葡萄糖苷（PNPG）为底物分别测定了四个化合物及紫甘薯茎叶提取物对α-葡萄糖苷酶的抑制作用。结果显示上述4个化合物及紫甘薯茎叶粗提物抑制α-葡萄糖苷酶的IC50值分别为：7.556 μg/mL、1.419 μg/mL、0.209 μg/mL、9.339 μg/mL和5.371 μg/mL，均远远低于阳性对照阿卡波糖的IC50（355.4 μg/mL），而进一步的酶抑制反应动力学分析结果显示化合物及提取物对α-葡萄糖苷酶表现为竞争性抑制类型。试验表明紫甘薯茎叶提取物具有显著的α-葡萄糖苷酶抑制作用，为甘薯茎叶资源作为降糖保健品或药品开发提供理论依据。

Chlorogenic acid (1), 4,5-O-caffeoylquinic acid (2), 3,5-O-caffeoylquinic acid (3) and 3,4-O-caffeoylquinic acid (4) were isolated and prepared from purple sweet potato leaves by high speed counter-current chromatography (HSCCC). Then the inhibitory effect of these compounds and crude extract of sweet potato leaves on α-glucosidase were examined by using PNPG as substrate. The results indicated that four compounds and crude extract of sweet potato leaves exhibited certain inhibitory effects on α-glucosidase, with IC50 value of 7.556 μg/mL, 1.419 μg/mL, 0.209 μg/mL, 9.339 μg/mL and 5.371 μg/mL, respectively, which were far less than the positive control acarbose (IC50 355.4 μg/mL). In addition, the kinetic analysis showed the inhibitory effects of the four compounds on α-glucosidase were competitive, and the Ki were 27.18 μg/mL, 2.06 μg/mL, 8.42 μg/mL and 19.58 μg/mL, respectively. Therefore, sweet potato leaf extract has significant α-glucosidase inhibition, and could provide a theoretical basis for sweet potato leaves as a resource of hypoglycemic drug development or health care.

湖南省科技厅资助（2012NK3088）