A cytotoxic alkaloid; inhibits the growth of K562 leukemia and SW1116 colon cancer cells (IC50s = 20 and 28 nM, respectively); induces apoptosis of K562 cells via upregulation of the Bax/Bcl-2 ratio, decreasing mitochondrial membrane potential, inducing cytochrome C release, and activation of caspase-3 and caspase-9; decreases MRP1-mediated doxorubicin efflux and restores sensitivity to doxorubicin in resistant K562 cells