<p>The objective of the study was to optimize the ultrasonic-assisted extraction of curdione, furanodienone, curcumol, and germacrone from <i>Curcuma phaeocaulis</i> <i>Valeton</i> (Val.) and investigate the antiproliferative activity of the extract. Under the suitable high-performance liquid chromatography condition, the calibration curves for these four tested compounds showed high levels of linearity and the recoveries of these four compounds were between 97.9 and 104.3%. Response surface methodology (RSM) combining central composite design and desirability function (DF) was used to define optimal extraction parameters. The results of RSM and DF revealed that the optimum conditions were obtained as 8 mL g<sup>−1</sup> for liquid–solid ratio, 70% ethanol concentration, and 20 min of ultrasonic time. It was found that the surface structures of the sonicated herbal materials were fluffy and irregular. The <i>C. phaeocaulis</i> Val. extract significantly inhibited the proliferation of RKO and HT-29 cells <i>in vitro</i>. The results reveal that the RSM can be effectively used for optimizing the ultrasonic-assisted extraction of bioactive components from <i>C. phaeocaulis</i> Val. for antiproliferative activity.</p
