Cytotoxic Activity of Compounds from Lichens of the Cerrado Biome in Brazil

Lichens are sources of numerous biologically active compounds and many of these have demonstrated antitumor potential. The purposes of this study were to evaluate the antiproliferative activity and selectivity of the following compounds isolated from lichens: atranorin and diffractaic, divaricatic, perlatolic, psoromic, norstictic, and protocetraric acids. Cytotoxicity tests based on sulforhodamine B were performed on normal cells (NIH/3T3, fibroblast) and cancer cell lines 786-0 (renal), MCF7 (breast), HT-29 (colon), PC-3 (prostate), and HEp2 (laryngeal). Diffractaic acid exhibited GI(50) values in the 58.6-98.9 mu M range. Divaricatic and perlatolic acids were the most active compounds, with GI(50) values of 9.8 and 15.5 mu M for PC-3 and MCF7 cells, respectively. Protocetraric acid proved active only against HEp2 cells (GI(50) = 41.4 mu M). Atranorin, psoromic acid, and norstictic acids were inactive against all the cells tested. Chemometrics was used to evaluate the effect of the compounds against the cell lines tested. PCA (Principal Component Analysis) based on GI(50) values separated compounds into two groups compared to doxorubucin, while HCA (Hierarchical Cluster Analysis) separated them into three groups based on SI values.