Abstract:

Three different plants of licorice, G. inflata, G. glabra and G. uralensis, were used as the research objects to compare the differences in the composition and activities. The content of liquiritin, glycyrrhizic acid and glabridin was determined by HPLC-DAD; the difference in total flavonoid content was compared by UV spectrophotometry, and the inhibition of tyrosinase and hyaluronidase activities was compared. The target compounds were extracted with 70% ethanol, and separated on an Agilent Poroshell 120 EC-C₁₈ （150 mm×4.6 mm, 2.7 µm） in gradient elution program using methanol and 0.05% phosphoric acid as mobile phase, at a flow rate of 1 mL/min at 30 ℃, and using a detection wavelength of 270 nm. The validated HPLC method shows good linear relationship with correlation coefficients larger than 0.998 85. The relative standard deviation （RSD） values of precision, stability and repeatability are less than 0.89%. The average recoveries are in the range of 97.50%-99.60% with the RSD values less than 2.09%. The analysis results show that the content of glycyrrhizic acid and glabridin are the highest inG. glabra, and the content of liquiritin is the highest in G. uralensis; the total flavonoid content of licorice ranks in a sequence that G. glabra > G. uralensis > G. inflata; The sequence of inhibition rate of tyrosinase isG. glabra > G. uralensis > G. inflate, and their IC₅₀ values are 7.36, 8.38 and 11.13 mg/L, respectively; the sequence of inhibition rate of hyaluronidase is G. inflata > G. uralensis > G. glabra, and their IC₅₀ values are 8.70, 9.19 and 10.45 mg/mL, respectively. The three kinds of licorice may have good whitening and anti-allergy effects because of their good inhibition of tyrosinase and hyaluronidase. To achieve the best effect, they need to be used separately.

Key words: licorice, high performance liquid chromatography, content determination, total flavonoids, whitening, anti-allergy