Abstract: Supercritical CO2 fluid extraction technique  was explored to extract total flavonoids from praecox leaves in northern areas of China. Single-factor design was used to determine main variables that influence extraction rate of total flavonoids. The optimal extraction conditions were achieved to be extraction temperature of 36 ℃, ethanol concentration of 50%, extraction pressure of 35 MPa, entrainer (absolute ethanol) amount of 1:15, entrainer amount 9% and extraction time of 40 min. Under the optimal extraction conditions, the extraction rate of total flavonoids was 23.24 mg/g. The supercritical fluid CO2 extraction can be used for the extraction of total flavonoids from praecox leaves with high extraction efficiency.

Key words: praecox leaves, supercritical fluid CO2 extraction, total flavonoids, extraction