Isolation Of Glabridin And Factors Influencing Its Stability

Glabridin is one specific isoflavan in Glycyrrhiza glabra (GLAB), one kind of active compounds possessing various pharmacological activities such as antioxidant. Isolation of glabridin was much difficult because of the varieties of flavoniods in GLAB. Moreover, degradation was recorded during the preparation and preservation of glabridin for its poor chemical stability. Therefore, in order to avoid the influence of preservation and isolation conditions on the purity of glabridin, determination, preparation and factors influencing stability of glabridin were studied during our research. The radical scavenging activities of licorice extract with different polarities were carried out as well.Glabridin was determined through high performance liquid chromatography (HPLC) method. Mobile phase was made up by a mixture of methanol-water with 0.2% acetic acid (7/3, v/v). HPLC analysis was carried out at a flow rate of 1.0 mL/min, column temperature of 25℃and detection wavelength of 282 nm. The content of glabridin in GLAB was 8.83‰under our established method.D101 macroporous resin was used to isolate glabridin. The detailed experimental parameters for glabridin purification were studied to obtain an optimized preparation method. The purity of glabridin in licorice extract can reach 42.97% under optimized method with a recovery of 67.79%.Glabridin stability was studied at seven different factors (temperature, illumination, humidity, oxidant, pH, solvent and oxygen). Content changes were determined through our established HPLC method. Results indicated that oxygen had no significant effect on glabridin stability at room temperature. The remaining six factors were closely related with the stability of glabridin. Moreover, illumination was the main factor.Four kinds of licorice extract with different polarities were prepared (water extract, acetone extract, chloroform extraction and petroleum ether extract). The radical scavenging abilities of extracts above towards O2-,·OH, NO, HClO, ABTS and DPPH were evaluated through spectrophotometer method. It turned out that chloroform extract had the highest radical scavenging ability.