NG,a novel PABA/NO-based derivative of oleanolic acid (OA),has been found to show potent antitumor activity both in vivo and in vitro.In the present study,NG could significantly reduce tumor volume and weight in the H22 solid tumor mouse model.Meanwhile,NG showed selective effects on the HepG2 cells including NO generation,cytotoxic effect and apoptosis,which were prevented by hemoglobin (NO scavenger).Moreover,NG-induced apoptosis of HepG2 cells was characteristic of intracellular reactive oxygen species (ROS) generation,loss of mitochondrial membrane potential (△ψm) and enhanced Bax-to-Bcl-2 ratio.The release of apoptotic inducing factor (AIF) and cytochrome c (Cyt c) from mitochondria and the activation of caspase-3,-9 were also detected,indicating that NG may induce apoptosis through a mitochondfial-mediated pathway.Taking together,these findings suggest that NO can be released from NG,which induces apoptosis through a ROS-mediated mitochondrial pathway.