Ionic liquid-based microwave-assisted extraction of chlorogenic acid from green coffee beans

Microwave-assisted extraction (MAE) utilizing a hydrophilic ionic liquid, 1-butyl-3-methylimidazolium tetrafluoroborate [BMIM)][BF₄], was employed to extract chlorogenic acid from green coffee beans using Box–Behnken response surface methodology (BRSM). The yield of chlorogenic acid was considered as a function of four independent variables, namely ionic liquid concentration (M), temperature (°C), wattage (W) and time (min). By analyzing a three-dimensional surface plot of the response surface and solving the regression model equation with Design Expert software, the optimal process conditions were determined. The result shows that an extraction temperature of 90 °C, microwave power of 800 W, ionic liquid concentration ([BMIM][BF₄]) of 1 M and extraction time of 3 min were the best conditions for the extraction of chlorogenic acid. Under these conditions (IL-MAE), the maximum observed yield of chlorogenic acid was found to be 7.31%, which was higher than the conventional method of chlorogenic acid extraction (6.0%) from green coffee beans. The isomers of chlorogenic acids were found to be similar in both the conventional and ionic liquid-based microwave-assisted extracts isolated from green coffee beans. Further confirmation of the method's reliability was provided by the study, indicating that (BMIM)(BF4)-based MAE is effective for extracting chlorogenic acid from green coffee.