Cytotoxicity and Modes of Action of the Methanol Extracts of Six Cameroonian Medicinal Plants against Multidrug-Resistant Tumor Cells

. The present study aims at evaluating the cytotoxicity of twelve parts from six Cameroonian medicinal plants on sensitive and drug-resistant cancer cell lines. We also studied the mode of action of the most active plants, Gladiolus quartinianus , Vepris soyauxii , and Anonidium mannii . Methods . The cytotoxicity of the extracts was determined using a resazurin assay. Flow cytometry was used for cell-cycle analysis and detection of apoptosis, analysis of mitochondrial membrane potential (MMP), and measurement of reactive oxygen species (ROS). Results . At 40 g/mL, three extracts showed a growth of CCRF-CEM leukemia cells by less than 50%. This includes the extracts from G. quartinianus (GQW; 25.69%), Vepris soyauxii leaves (VSL; 29.82%), and Anonidium mannii leaves (AML; 31.58%). The lowest IC 50 values below 30  μ g/mL were obtained with GQW, AML and VSL against 7/9, 8/9, and 9/9 tested cancer cell lines, respectively. The lowest IC 50 values for each plant were 4.09  μ g/mL, and 9.14  μ g/mL (against U87MG.Δ EGFR cells), respectively, for VSL and AML and 10.57  μ g/mL (against CCRF-CEM cells) for GQW. GQW induced cell cycle arrest between G0/G1 and S phases, whilst VSL and AML induced arrest in G0/G1. All three extracts induced apoptosis in CCRF-CEM cells by loss of MMP, whilst AML also enhanced production of ROS. Conclusion . The three active plants may be a source for the development of new anticancer drugs.