Abstract:

Abstract: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 (IC₅₀) experiment was divided into 7-dose groups. The inhibitory rate of drugs was calculated,and the IC₅₀ 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(P<0.001,P<0.001,P<0.01);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(P<0.01),the IC₅₀ of GBE on sucrase was 0.758 6 g·L^-1,and the IC₅₀ 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.

Key words: ginkgo biloba extract;α-glucosidase;extrasomatic inhibition;blood glucose reduction