Diterpenes from Plectranthus spp.: a ROS-induced cytotoxicity study

Plants from the Plectranthus genus are commonly known for their medicinal properties, and their applications are vast in traditional medicine. Often accountable for these properties, bioactive secondary metabolites such as diterpenes are present in these plants, and some possess cytotoxic properties. Abietane diterpenes 7α-acetoxy-6β-hydroxyroyleanone, 7β,6β-dihydroxyroyleanone, 6,7- dehydroroyleanone, and parvifloron D are examples of such class of bioactive diterpenes. These abietanes are obtained from Plectranthus genus plants as their major compounds. In this work, the cytotoxic properties of these abietanes have been studied. This property was evaluated through MTT assays on A549 cells and CCRF-CEM cells. In addition, the level of intracellular Reactive Oxygen Species (ROS) in these cells was also measured. Our study has revealed that on CCRF-CEM cells, there is a slight increase of the ROS levels after exposure to all compounds. Nevertheless, on A549 cells the levels of ROS increase approximately 10-fold, with notorious increase after exposure to 7β,6β-dihydroxyroyleanone, which can induce cytotoxicity due to ROS accumulation on cells. In conclusion, this study proves the therapeutic potential of Plectranthus-derived diterpenes and validates its use in traditional medicine.