Optimization of Microwave‐Assisted Extraction of <i>Curcuma zedoaria</i> Rhizome: A Comparative Study of Castor Oil and Sesame Oil

ABSTRACT Curcuma zedoaria (Christm.) Roscoe is a curcuminoid‐rich plant with potential applications in cosmetic products. This study aimed to optimize the microwave‐assisted extraction (MAE) conditions for C. zedoaria rhizomes using castor oil and sesame oil as solvents. A full factorial design was employed, investigating microwave power levels of 600 and 800 W, and microwave times of 30 and 90 s. The results showed that microwave time significantly affected extraction yield, and individual and total curcuminoid content while microwave power did not. The optimal conditions for maximizing extraction yield and total curcuminoid content were 600 W for 90 s with castor oil, and 600 W for 80 s with sesame oil. Stability testing revealed that curcuminoids were more stable in castor oil than in sesame oil when stored at 4°C, 30°C/75% relative humidity (RH), and 40°C/75% RH over 3 months. In conclusion, this study demonstrates that MAE is an effective method for extracting curcuminoids from C. zedoaria , with castor oil showing superior preservation of curcuminoid content. These findings suggest that castor oil could be a preferable solvent for the extraction and stabilization of curcuminoids in C. zedoaria for cosmetic applications.