Abstract: On the basis of single-factor experiments, three key process parameters including ethanol concentration, solid/liquid ratio and extraction number for the ultrasound-assisted extraction of total flavonoids from the stems and leaves of Gynura divaricata (L.) DC. were optimized by Box-Behnken experimental design coupled with response surface methodology. The inhibitory effects of crude total flavonoid extract and its different solvent fractions on α-glucosidase were investigated. The results showed that the optimal ultrasound-assisted extraction conditions were 55% ethanol as extraction solvent at a material/liquid ratio of 1:35 (g/mL) for 4 repeated extractions. Under these conditions, the actual extraction yield of total flavonoids was 3.071%, which was basically consistent with the predicted value, 3.095%. HPLC analysis revealed that the major components in crude extract had the absorption characteristics of flavonoids.

Key words: Gynura divaricata (L.) DC., flavonoids, ultrasound-assisted extraction, response surface methodology, inhibitory activity on α-glucosidase