Optimization of extraction method and antioxidant activity of total flavonoids from stems and leaves of Fagopyrum dibotrys

In this study, ultrasonic-assisted aqueous two-phase extraction technology was used to optimize the extraction method of flavonoids from Fagopyrum dibotrys, and the antioxidant properties of the extracted active substances were studied. To optimize the extraction process, a multi-factor response surface test was conducted using ammonium sulfate mass fraction, liquid-to-solids ratio, and ultrasonic time as independent variables. The total flavonoid content in the extract served as the evaluating parameter. The antioxidant capacity of F. dibotrys extract was evaluated by DPPH, OH⁻, O₂⁻ free radical scavenging rate. The results showed that the optimal preparation conditions of total flavonoids from F. dibotrys were as follows: ammonium sulfate mass fraction 15%, liquid-solid ratio 38 ꞉ 1, ultrasonic time 47 min, and the total flavonoids content was 78.52 mg·g⁻¹. The IC₅₀ values of DPPH, OH⁻, O₂⁻ free radical scavenging rate of F. dibotrys extract were 0.118 2, 4.071 0, 25.380 0 mg·mL⁻¹, respectively.