<div><p>In this study, we found that two sesquiterpene lactones, isobutyroylplenolin and arnicolide D, from <i>Centipeda minima</i> L. (Compositae) exerted stronger cytotoxic activity than cisplatin on the human colon carcinoma HT-29 cell line. Furthermore, the cytotoxicity of these two compounds on normal cells was weaker than that of cisplatin. Treatment with isobutyroylplenolin and arnicolide D increased the levels of intracellular reactive oxygen species and decreased the levels of nuclear factor-κB protein, resulting in cell cycle arrest in G1 phase and apoptosis. We also discuss the difference in structure and activity between these two compounds.</p></div