Cytotoxic activity of halogenated sesquiterpenes from Laurencia dendroidea

Red algae of the genus Laurencia J. V. Lamouroux are found in tropical and subtropical regions throughout the world and are an extremely rich source of active secondary metabolites with diverse structural features. In the present study, 6 sesquiterpenes (obtusol, (-)-elatol, dendoidiol, debrome-elatol, triquinane, and obtusane) isolated from Laurencia dendroidea were investigated for their cytotoxicity, using 4 cancer cell lines (U937, Jurkat, B16F10, and Colo-205). Among all sesquiterpenes tested, obtusol and (-)-elatol showed a promising activity in the treatment of Colo-205 strain, with IC₅₀ of 1.2 ± 1.4 and 2.5 ± 1.3 μg/ml, respectively. In addition, fluorescence microscopy results indicated that, at 100 μg/ml, obtusol induced apoptosis at 79% and (-)-elatol at 95%. Activation of Caspases 2, 4, 6, and 8 showed to be involved in (-)-elatol activity and only Caspase 6 in obtusol activity. These data demonstrated the effective apoptosis-inducing activity of the sesquiterpene (-)-elatol and obtusol in the treatment of Colo-205 strain. Therefore, more studies should be done so that the sesquiterpenes (-)-elatol and obtusol might become promising chemotherapy.