Screening Of α-glucosidase Inhibitoring Chinese Herbals And The Evaluation Of Their Hypoglycemic Effect

ObjectiveTo screen the Chinese herbal medicine which has strongest inhibitory effect on a-glycosidase and to explore its extraction technology, inhibit types, hypoglycemic effect and mechanism of action.Methods1. Twenty kinds of Chinese herbal medicines were selected according to the long-term practice reports about Chinese herbal medicine therapy for diabetes and the lists of Chinese medicine science and healthcare products. Then, the water extraction and the alcohol extraction were used to prepare extratcts. The inhibitory effect of twenty kinds of Chinese herbs on a-glycosidase was observed by the glucose oxidase method with maltose as substrate and acarbose as positive control.2. The single factor experiment method and the orthogonal design L9(34)were used to select the optimum technology to the Chinese herbal medicine (Cortex Mori) which had the strongest inhibitory effect on a-glycosidase.3. The enzyme concentration-reaction velocity graphical method was used to determine if the inhibition reaction type was reversible or not. The inhibitory type was detected by the Lineweaver-Burk wave according to the data.4. Mice were randomly divided into different groups. Mice were intragastrically administered for seven days, once a day, and after the last day, oral maltose tolerance test was determined. Blood glucose levels were detected by blood glucose meter.5. Diabetic mice model was induced by streptozotocin. The methods of grouping, administering and blood glucose levels detecting were the same to normal mice and diabetic mice.6. Weighing the amount of food intake and water drinking before administration in mice of each group every day and weight every other day in the experiment.Results1. All of the twenty kinds of Chinese herbs could inhibit the activity of a-glucosidase, and the water extracts of Folium Mori, Cortex Mori, Fructus Corni, Rhizoma Polygonati Odorati and Cortex Lycii all showed stronger inhibitory activity, the inhibition rates were 97.56%,95.89%,72.73%,80.22% and 59.06% respectively at the concentration of 1000 mg/ml, and the ethanol extracts of Cortex Mori, Folium Mori, Cortex Lycii, Fructus Corni and Radix Puerariae all showed stronger inhibitory activity, the inhibition rates were 98.94%,94.97%,94.78%,84.27% and 81.00% respectively at the concentration of 1000 mg/ml. The extracts of these Chinese herbs which had stronger inhibitory activity all showed certain concentration-effect relationship, and the inhibitory effect of Cortex Mori was the most similar to acarbose.2. The study showed that the best extraction technology of Cortex Mori water extraction was:solid-liquid ratio 1:10, three times extraction, One and a half hours each time, and the best extraction technology of Cortex Mori ethanol extraction was: 45% ethanol, solid-liquid ratio 1:8, extract twelve hours.3. Both the water extracts and the ethanol extracts from Cortex Mori showed non-competitive inhibition effects on a-glycosidase.4. Compared with the control group, Cortex Mori extracts and acarbose all can decrease postprandial blood glucose level in normal mice that have been disposable gastric perfused malt sugar after half an hour and one hour(P<0.05). There were not statistical significance between Cortex Mori extracts group, acarbose group and the control group in weight, food intake and water drinking of normal mice(P>0.05).5. The study showed that the high dosage Cortex Mori water extracts and the high dosage Cortex Mori ethanol extracts can significantly decrease postprandial blood glucose level of STZ-induced diabetic mice that have been disposable gastric perfused malt sugar after half an hour, one hour, one and a half hours and two hours(P<0.05), and there was similar to acarbose(P>0.05). Compared with the control group, the low dosage Cortex Mori water extracts can decrease blood glucose level after half an hour(P<0.05) and the low dosage Cortex Mori ethanol extracts can decrease blood glucose level after half an hour, one hour and one and a half hours(P<0.05). Compared with the control group, Cortex Mori extracts and acarbose all can remarkably influence the weight, food intake and water drinking of STZ-induced diabetic mice(P<0.05). ConclusionsThe study indicated that the twenty kinds of Chinese herbs all showed some inhibitory activities. The inhibitory activity of Cortex Mori was the strongest among them, which was similar to the effect of acarbose. Both Cortex Mori water extracts and Cortex Mori ethanol extracts showed non-competitive inhibition effects onα-glycosidase. All the Cortex Mori water extracts and the Cortex Mori ethanol extracts can decrease the postprandial blood glucose peak after maltose load in normal mice and STZ-induced diabetic mice. These extracts can reduce food intake and water drinking and increase weight of STZ-induced diabetic mice. It may be one of the hypoglycemiac mechanisms to inhibit the intestinal assimilation of malt sugar.