Abstract: In order to study the aqueous two-phase extraction of total flavonoids in fruit of Rosa davurica Pall., both single factor and orthogonal test methods were applied to optimize the extraction conditions. The antioxidant ability of total flavonoids was evaluated according to the clearance ratio and reducing power to superoxide anion free radicals, DPPH free radical, hydroxyl free radical, sodium nitrite and ABTS radical cations. The results showed that the optimum extraction conditions were the volume fraction of absolute ethyl alcohol 27%, mass concentration of ammonium sulfate 0.21 g/mL, volume fraction of extraction solution 22%, and addition of sodium hydroxide 2.0 g, respectively. The average extraction ratio could reach 91.81% under the optimum extraction conditions. The extraction solution showed significant clearance ability to ABTS radical cations, hydroxyl free radical, superoxide anion free radicals with the clearance rates of 90.27%, 89.60% and 96.73% as the mass concentrations of total flavonoids 0.12, 0.30 and 0.60 g/L, respectively. They were stronger than those of Vc. The clearance ability of extraction solution to DPPH free radical and nitrite was weaker than that of Vc. The extraction solution also had some reducing power.

Key words: fruit of Rosa davurica Pall., total flavonoids, aqueous two-phase, antioxidant ability