Abstract

Folium eucommiae is a traditional Chinese medicinal herb. Ultrasonic-assisted extraction (UAE) technique was developed for the fast extraction of chlorogenic acid from F. eucommiae leaves. Several influential parameters of the UAE procedure (solvents, extraction cycles, extraction temperature, solvent to material ratio, irradiation time and solvent concentration) were investigated for the optimization of the chlorogenic acid extract using single factor and Box-Behnken experimental design. Response surface methodology analysis showed good correspondence between experimental and predicted values. It was found that the most effective parameter was solvent to material ratio, which was in good agreement with the experimental value. The adjusted coefficient of determination (R_adj²) for the model was 96.1%. Probability value (P < 0.001) demonstrated a very high significance for the regression model. The maximum yield of chlorogenic acid of 0.77 mg/g with UAE was obtained by dual extraction with ethanol to material ratio of 17/1 v/m, irradiation time of 25 min, ethanol concentration of 52%, extraction temperature of 50°C and ultrasonic frequency of 5 kHz. The optimal yield with UAE was slightly lower than that of Soxhlet extraction and higher than that of heat reflux extraction. The extracts exhibited high scavenging effects on DPPH radical with increasing concentration from 0.1 to 0.9 mg/ml. The extracts also exhibited a quite strong concentration-dependent inhibition of hydroxyl radical.

Key words: Folium eucommiae, chlorogenic acid, ultrasonic-assisted extraction, response surface methodology.