Abstract: In this paper, orthogonal array design L9(34) was employed to optimize the extraction conditions of total flavonoids from Radix Puerariae residue left after pueraria root powder extraction. The effects of extraction temperature, ethanol concentration, extraction time and material-to-liquid ratio on extraction rate of total flavonoids were probed. Meanwhile, a HPLC method to determine puerarin content in Radix Puerariae was presented based on optimized extraction process. The optimal extraction conditions were determined as follows: ethanol concentration 70%, reflux time 150 min, reflux temperature 80 ℃, and material-to-liquid ratio 1:40, under which, the contents of total flavonoids in Radix Puerariae, Radix Puerariae residue and pueraria root powder were 46.11, 32.41 mg/g and 11.23 mg/g, and of puerarin 40.63, 21.24 mg/g and 4.71 mg/g, respectively. From these results, we drew the conclusion that Radix Puerariae residue is rich in total flavonoids and puerarin and that the optimized extraction process can be used for the extraction of total flavonoids and puerarin from Radix Puerariae residue.

Key words: Radix Puerariae residue, total flavonoids, puerarin, high performance liquid chromatography, orthogonal array design