Objective: To optimize preparation technology of Glycyrrhizae Radix et Rhizoma flavonoids microsponges and investigate its in vitro release. Method: Glycyrrhizae Radix et Rhizoma flavonoids microsponges were prepared by quasi-emulsion solvent diffusion method

taking yield of microsponges

encapsulation efficiency and dispersion coefficient as indexes

central composite design-response surface methodology was adopted to investigate effect of dosage of polyvinyl alcohol(PVA)

ratio of drug and ethyl-cellulose

stirring speed on preparation procedure of the microsponges.Encapsulation efficiency of the microsponges was determined by UV spectrophotometry.The content of six major ingredients in Glycyrrhizae Radix et Rhizoma flavonoids were investigated simultaneously by HPLC

detection wavelength was 300 nm

mobile phase was acetonitrile-methanol-0.2% phosphoric acid aqueous solution for gradient elution.Difference of in vitro release between Glycyrrhizae Radix et Rhizoma flavonoids and the microsponges was compared by dialysis method. Result: Optimum preparation technology of the microsponges were as follows: PVA amount of 2.69%

drug-ethyl-cellulose(6:1)

stirring speed of 1 100 r·min-1

stirring time of 4 h.Within 8 h

cumulative release rates of liquiritin

isoliquiritin

liquiritigenin

isoliquiritigenin

licochalcone A and glabridin in Glycyrrhizae Radix et Rhizoma flavonoids were 87.47%

86.83%

76.98%

78.48%

86.58% and 56.58%;within 24 h

cumulative release rates of these components were 91.45%

89.74%

77.57%

82.64%

87.74% and 67.74%

respectively. Conclusion: Glycyrrhizae Radix et Rhizoma flavonoids microsponges are homogeneous with an obvious sustained release property

and the optimum preparation technology is stable and simple.