IC50 values ranging from 10.13 μg/mL (towards CEM/ADR5000 cells) to 72.01 μg/mL [towards resistant colon carcinoma HCT116 (p53−/−) cells] for Pachypodanthium staudtii roots and from 0.11 μg/mL (towards CCRF–CEM cells) to 108 μg/mL (towards P-glycoprotein-over-expressing CEM/ADR5000 cells) for doxorubicin were obtained in the eight other cancer cell lines studied. This evidence concerns the gene ABCB1 and colon carcinoma.