Optimization and Kinetic Modeling of Rosmarinic Acid Extraction from Orthosiphon stamineus

The optimization and kinetic of rosmarinic acid extraction from Orthosiphon stamineus were investigated in this study. In the preliminary study, the extractions were carried out to identify the optimal ethanol concentration. Then, the optimal ethanol concentration was used to optimize the extraction variables (solventto- solid loading ratio, temperature and time) by central composite design. The optimum conditions for the rosmarinic acid extraction were at the concentration of ethanol, 70% v/v; solvent-to-solid loading ratio, 9.14; extraction temperature, 56.53°C; and extraction time, 3 hours. Subsequently, this study used six proposed models to describe the kinetic of the rosmarinic acid extraction. Two-site kinetic model gave the best fit for the experimental data with the highest coefficient of determination, R2 (0.976) and the smallest values of root mean square error (RMSE) (1.522). The goodness of fit is due to the presence of the rate constants of both fast and slow released fractions in the model. Hence, two-site kinetic model is the most appropriate model to describe the rosmarinic acid extraction from O. stamineus in a reflux extraction system.