| a-Glucosidase inhibitors can retard the absorption of glucose to improve postprandial hyperglycemia effectively. They are applied for the treatment of diabetes extensively. In addition, a-glucosidase inhibitors are vital for the processing of glycoproteins and glycolipids, so these inhibitors might exhibit antiviral, antimetastatic and immunostimulatory activities through interference with the normal processing of glycoproteins and glycolipids.Radix glycyrrhizae is the dried root and rhizome of Glycyrrhiza uralensis Fisch., Glycyrrhiza inflata Bat. or Glycyrrhiza glabra L.. It was reported that radix glycyrrhizae has many types of pharmacological action, such as antivirus, anti-ulcer, antibiosis, antioxidation, antitumor, detoxication, liver-protecting. In recent studies, the aqueous extract of radix glycyrrhizae was found to have a-glucosidase inhibitory activity. It is significant to extract and isolate a-glucosidase inhibitors from radix glycyrrhizae.In this study, the aqueous extract of Glycyrrhiza uralensis Fisch. was extracted by petroleum ether, ethyl acetate and n-butanol according to the polarity, successively. The inhibitory ratio of enzymatic activity (IRE) of every fraction was determined. The results suggested that the IREs of four fractions were 68.93%, 83.2%, 32.17% and 10.79%, respectively. Compared with the IRE of aqueous extract 69.77%, the IRE of ethyl acetate fraction was higher and it was shown to be a fast-binding, dose-dependent and competitive model with a Ki value of 34μg-mL-1.Secondly, glycyrrhizic acid, glycyrrhetinic acid, flavonoids of glycyrrhiza, alkaloids of glycyrrhiza and glycyrrhiza polysaccharides were extracted and isolatedfrom Glycyrrhiza uralensis Fisch., and their IREs were -2.88%, 85.4%, 87.89%, 40.72% and 0.97%, respectively. Flavonoids of glycyrrhiza and glycyrrhetinic acid lowered plasma glucose level after sucrose being loaded onto all rats.The above results suggested that a-glucosidase inhibitors were located in flavonoids of glycyrrhiza. Guided by the a-glucosidase inhibitory test in vitro, we further isolated and identified glycyrol, liquiritin and B-sitosterol from the flavonoids by means of physicochemical constants and spectral analysis. Among them glycyrol had the strongest a-glucosidase inhibitory activity and was a fast-bindging, reversible, noncompetitive a-glucosidase inhibitor with al￡ value of 26.8xlO"3yagmL"1.In the second part of this study, the dispersible tablets of flavonoids of glycyrrhiza was studied. We optimized prescription and preparation technology through preliminary optimization and orthogonal experiment by using disintegration time as valuable indicator. The disintegration time, dispersal homogeneity and dissolution of the dispersible tablets met the demands of quality, and the stability was also met.The results of this study provide a reference for the further study on Glycyrrhiza uralensis Fisch. about mechanism of lowering plasma glucose and application of new preparation. |
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