Influence of the Extraction Solvent and of the Altitude on the Anticancer Activity of Lebanese Eucalyptus camaldulensis Extract Alone or in Combination with Low Dose of Cisplatin in A549 Human Lung Adenocarcinoma Cells

Background: Lung cancer is the second most common cancer worldwide. Eucalyptus plant extract has been shown to have anti-neoplastic effects. We investigated the antitumor effect of ethanolic and aqueous extracts of Eucalyptus camaldulensis collected at different altitudes on A549. In addition, we evaluated the additive effect of its combination with low-dose cisplatin (CDDP). Methods: Qualitative and quantitative analyses of secondary metabolites present in the plants were carried out. The antioxidant and cytotoxic activities of the different extracts on A549 were evaluated using the 2.2-diphenyl-1-picrylhydrazyl radical scavenging activity and neutral red assay, respectively. The cytotoxic effect of the combination of certain extract concentrations with low-dose CDDP on A549 cells was studied. Results: In the Ethanoic extract, a higher number of active substances and antioxidant activities were observed. The four E. camaldulensis extracts showed cytotoxic activity on A549 cells, with a higher cytotoxicity for the Ethanoic extract and the sea-level altitude species. Moreover, the dual exposure of cells to both E. camaldulensis extracts and a low dose of Cisplatin showed an additional cytotoxic effect on A549 cells in certain concentrations. Conclusions: This study opens novel therapeutic options in combinational therapies of Eucalyptus camaldulensis with low-dose CDDP for the treatment of adenocarcinoma cells of human lungs.