Cytotoxic activity of some lichen extracts on murine and human cancer cell lines

Eight lichens were extracted successively with n-hexane, diethyl ether and methanol using a Soxhlet process. The cytotoxic activity of the 24 lichen extracts was evaluated in vitro using two murine (the L1210: lymphocytic leukaemia, and the 3LL: Lewis lung carcinoma) and four human (the K-562: chronic myelogenous leukaemia, the U251: glioblastoma, the DU145: prostate carcinoma, and the MCF7: breast adenocarcinoma) cancer cell lines and non-cancerous cells, the Vero cell line (African green monkey kidney cell line). The MTT assay revealed significant cytotoxicity (IC50 < or = 20 microg/ml) on one of the tested cancer cell lines for at least one extract of each lichen species. Some extracts of Cladonia convoluta, Cladonia rangiformis, Parmelia caperata, Platismatia glauca and Ramalina cuspidata demonstrated interesting activities particularly on human cancer cell lines as good selectivity indices were recorded (SI > 3).