Iso-caryophyllene, a sesquiterpene, is present in several essential oils from vegetable species. In previous work, iso-caryophyllene was found cytotoxic against in vitro culture cell lines but its mechanism of action is still unknown. Reactive oxygen species (ROS) and lipid oxidation induced by iso-caryophyllene were assessed using DCFH-DA and BODIPY-C11, respectively. The results show that iso-caryophyllene induces significant overproduction of ROS by about 187 % at 100 µM and lipid oxidation, which are both partially inhibited by a-tocopherol. The effect of isocaryophyllene on membrane permeabilization was evaluated using calcein-AM assay that show that iso-caryophyllene causes membrane permeabilization and cell shrinking. a-Tocopherol significantly prevents membrane permeabilization, cell shrinking and cell death, suggesting that lipid oxidation is in part implied in the cytotoxicity. Electrochemical experiments indicate that the superoxide anion reacts with iso-caryophyllene and possibly form oxidized derivatives which could initiate lipid oxidation. Interestingly, superoxide anion reacts more readily with a-tocopherol in comparison with iso-caryophyllene which could explain its protective effect on cellular membrane
