Study On The Extraction, Content Determination And Antioxidant Activity Of Flavonoids From Licorice

The saponins and flavonoids are the main active ingredients in licorice. As two importantcompounds contained in flavonoids, isoliquiritigenin and liquiritigenin have diversepharmacological effects such as anti-inflammatory, anti-HIV, anti-tumor. Therefore they willhave broad development and application prospects. In this paper, the method for contentdetermination of isoliquiritigenin and liquiritigenin was established through the enrichment oftotal flavonoids in licorice, combining with the method for the content determination ofglycyrrhizin in licorice from Pharmacopoeia2010. And further determination was made forthe antioxidant activity of isoliquiritigenin and liquiritigenin.1. On the base of single factor investigation, uniform Design was used to optimize theeffects of the ultrasound-assisted processing parameters for extraction of total flavonoids fromlicorice. There independent variables including methanol concentration (%), extraction time(min) and solid-liquid ratio (g/mL) were studied. Relevant parameters of theultrasound-assisted extract of the highest concentration of total flavonoids are as follows:methanol concentration of70%, extraction time of30min, the solid-liquid ratio of1:20(g/mL). Under optimized conditions the total flavonoids yield was3.28%.2. The method for determination the content of isoliquiritigenin and liquiritigenin fromlicorice was established by isocratic elution and time table detection wavelength by HPLC.The chromatographic separation was performed on Hyporsil ODS2(4.6mm×250mm,5μm)column eluted with detection wavelength time series of276nm (0~25min)and360mn (25~70min), the mobile phase of CH3O:H2O=45:55, the flow rate of0.8mL/min, the injectionvolume of10μL. At the chromatographic conditions, isoliquiritigenin (R2=0.9996) andliquiritigenin (R2=0.9991) has a good linear relationship,and the average recoveries are97.9%and98.3%respectively, RSD are1.3%and1.64%respectively. 3. Response surface methodology was employed using a Box-Behnken design ofexperiments to optimize the ultrasound-assisted processing parameters for extraction ofisoliquiritigenin from licorice. The following independent parameters were investigated:methanol concentration (%), extraction time (min) and solid-liquid ratio (g/mL). The optimalconditions for obtain the highest isoliquiritigenin were70%as methanol concentration,35minas extraction time and1:18(g/mL) as solid-liquid ratio. In conclusion, the yield ofisoliquiritigenin was0.3%. In addition, the quadratic polynomial model for this technologywas obtained. A correlation coefficient was estimated to be0.9446, which demonstrates theeffectiveness of the model. The P-value of the regression model was less than0.0001, whichmean the model was notable.4. By Vc and BHT as the the reference antioxidant radical scavenger compounds, theantioxidant activity of isoliquiritigenin and liquiritigeninwas evaluated using three establishedmethods such as hydroxyl radical, superoxide anion and DPPH in vitro radical scavenging.The result of the free radicals scavenging activeities was detected by UV detector. There wasobserved a correlation between samples concentration and antioxidant potency. The resultshow the scavenging capacity on the three radicals follows in descending order of Vc,isoliquiritigenin, liquiritigenin, BHT.