Optimization of Modified Supercritical CO2 Extraction of Chlorogenic Acid from the Flower Buds of Lonicera japonica Thunb and Determination of Antioxidant Activity of the Extracts

Chlorogenic acid from the flower buds of Lonicera japonica Thunb was extracted by modified supercritical CO2 with subsequent analysis by HPLC. Response surface methodology was utilized to optimize process parameters. The effects of pressure range from 100 to 300bar, temperature range from 50 degrees C to 80 degrees C, and various concentration of ethanol used as co-solvent range from 20% to 60% (ethanol:water, v/v) on the yield of chlorogenic acid were studied in supercritical CO2 extraction. The free radical-scavenging activity of the extracts was evaluated with 2,2-diphenyl-1-picrylhydrazyl assay. Two quadratic models were used to fit the effects of the variables on chlorogenic acid yield and the free radical-scavenging activity of the extracts, respectively. The optimized extraction conditions were 32% ethanol (v/v), temperature of 74 degrees C, and pressure of 289bar, producing a maximum yield of 5.51% with IE50 0.286mg/mL inside the experimental domain.