Members of the family Anacardiaceae are known to contain a number of biologically active substances, such as phenolic lipids, alkyl-catechols and alkyl-resorcinols. In the present study, human cancer cell lines, DU-145 cells (androgen-insensitive prostate cancer cells), KB cells (human epidermoid cells), and human melanoma cell line, M14, were treated for 72 h with 0.59-9.5 microM litreol (3-[pentadecyl-10-enyl-catechol]), a alkyl-catechol isolated from Lithraea caustica (Molina) Hook. & Arn. The results showed, for the first time, that litreol inhibited cancer cell viability in a dose-dependent manner. In addition, the treatment with this compound at 0.59-1.18 microM concentrations induced apoptotic cell death, demonstrated by the fragmentation of genomic DNA and by a significant increase of caspase-3 activity. The significant production of reactive oxygen species (ROS) evidenced in these experimental conditions could trigger the apoptosis cascades. Taken together, these results demonstrate that litreol attenuate the growth of human cancer cells, at least in part, triggering an apoptotic process, and they may offer a further impulse to the development of its analogues with more potent efficacy against human cancer cells.