Background: Eugenol is a major component of the essential oil isolated from Eugenia caryophyllata (Myrtaceae), and has been widely used as a traditional medicine. In this study, the effects of eugenol on the cytotoxicity, induction of apoptosis and putative pathways of its actions were investigated in human promyelocytic leukemia cells (HL-60).
Methods: After applying eugenol to cultured HL-60, the changes in the mitochondrial membrane potential of the cells were monitored after double staining with propidium iodide and rhodamine 123, with 2', 7'-dicholorofluorescin diacetate was used to measure of levels of reactive oxygen species (ROS)
Results: Eugenol was shown to be a potent inducer of apoptosis; transducing the apoptotic signal via ROS generation; thereby, inducing mitochondrial permeability transition (MPT) and cytochrome c release to the cytosol. The production of ROS, mitochondrial alteration and subsequent apoptotic cell death in eugenol-treated cells were blocked by the antioxidant, N-acetylcystein (NAC).
Conclusion: Taken together, the present study has demonstrated that eugenol induces ROS-mediated mitochondrial permeability transition and resultant cytochrome c release.

Keywords: Eugenol, HL-60 cells, Apoptosis, Reactive oxygen species, Cytochrome c