银杏叶提取物对α-葡萄糖苷酶的抑制作用及其降血糖作用机制

Inhibitory effect of ginkgo biloba extract on alpha-glucosidase and its hypoglycemic mechanism

目的:通过体外药效学实验研究银杏叶提取物(GBE)对α-葡萄糖苷酶的抑制作用,探讨其降血糖的作用机制,为开发利用银杏叶资源提供实验依据。方法:提取大鼠小肠中的α-葡萄糖苷酶液,利用葡萄糖试剂盒测定酶活力;体外抑制实验分为正常对照组、阳性对照组及GBE高、中、低剂量组(10.0、5.0、2.5 g.L-1),对反应体系中的葡萄糖浓度进行测定,计算药物对蔗糖酶的抑制率;离体器官实验分为正常对照组、阴性对照组、阳性对照组和GBE高、中、低剂量组(10.0、5.0、2.5 g.L-1),对反应体系中的淀粉光密度值进行测定,计算药物对淀粉酶的抑制率;半数抑制率(IC50)实验将GBE分为7个剂量组,分别计算药物对α-糖苷酶的抑制率及IC50;抑制曲线实验分为正常对照组、阳性对照组及GBE组,计算反应速率,以底物浓度的倒数作为横坐标,以反应速率的倒数作为纵坐标,绘制抑制曲线。结果:大鼠小肠酶活力值为67.2活力单位。与正常对照组比较,GBE高、中、低剂量组蔗糖酶抑制率明显增加(P<0.001,P<0.001,P<0.01);与正常对照组比较,GBE高剂量组大鼠小肠中淀粉酶抑制率明显增加(P<0.01);GBE对蔗糖酶的IC50值为0.758 6 g.L-1,对淀粉酶的IC50值为0.910 1 g.L-1;GBE组趋势线与正常对照组斜率相近,且截距大于正常对照组趋势线。结论:GBE对α-糖苷酶具有良好的抑制作用,其作用机制为反竞争性抑制。

Objective To study the inhibitory effect of ginkgo biloba extract（GBE） on alpha-glucosidase by pharmacodynamic experiments in vitro,discuss the hypoglycemic mechanism,and provide experimental evidence for exploration and utilization of GBE.Methods The alpha-glucosidase was extracted from the small intestine of rats.The activity of α-glucosidase was determined by glucose kit.The inhibitory experiment in vitro was divided into normal control,positive control,and different doses of GBE（10.0,5.0,2.5 g·L-1） groups.The concentration of glucose in the reaction system was detected and the inhibitory rate of drugs was calculated.The ex vivo experiment was divided into normal control,negative control,positive control,and different doses of GBE（10.0,5.0,2.5 g·L-1） group.The optical density value of starch in the reaction system was determined and the inhibitory rate of drugs was detected.The 50% inhibitory concentration（IC50） experiment was divided into 7-dose groups.The inhibitory rate of drugs was calculated,and the IC50 was calculated.The inhibitory curve experiment was divided into normal control,positive control,and GBE group and the reaction rate was calculate.The reciprocal of concentration of substrate was used as abscissa,and the reciprocal of reaction rate as ordinate,and the inhibitory curves were drawn.Results The activity of α-glucosidase in rat small intestine was 67.2 μmol·L-1·min-1.The inhibitory experiment showed that high,moderate,low dose GBE inhibited the activity of alpha-glucosidase compared with normal control group（P0.001,P0.001,P0.01）;the ex vivo experiment results indicated that high dose GBE inhibited the hydrolytic effect of amylase from the segments of small intestine efficiently compared with normal control（P0.01）,the IC50 of GBE on sucrase was 0.758 6 g·L-1,and the IC50 of GBE on amylase was 0.910 1 g·L-1.Conclusion GBE has superior inhibition on α-glucosidase,and its mechanism is uncompetitive inhibition.