Avaliação da atividade anticancerígena de óleos essenciais de cinco espécies de Lippia (Verbenaceae)

Abstract

Despite the great progress in the treatment and progressive control of cancer, significant gaps still remain. Terpenoids which were found in the essential oils of several species from the genus Lippia were reported as potential anticancer compounds for some types of tumors. Consequently, this study aimed to investigate the possible pharmacological property as anticancer agent against tumor cell lines of compounds present in the essential oil of five Lippia species. The results showed, through the MTT assay, cytotoxic effect on mouse colon carcinoma cell lines CT26.WT and human skin melanoma MeWo with IC50 and effect on the cell viability above 50% under the use of essential oils of L. alba chemotypes geraniol and carvone, L.sidoides, L. salviifolia, L. rotundifolia and L. lacunosa. The cell cycle was arrested in G0/G1 phase after 24 h treatment of of MeWo with the oils of L. alba chemotypes geraniol (50 μg/ml) and carvone (100 and 150 μg/mL) and L. rotundifolia (200 μg/mL). Additionally, the oils of L. alba geraniol (200 μg/mL for 24 h) and L. lacunosa (10, 50, 100 and 200 μg/mL) resulted in cell death of MeWo, characterized by high DNA fragmentation, and it was confirmed as apoptosis for the L. alba geraniol oil by TUNEL assay. As far as the CT26.WT cell line is concerned, the oil of L. alba geraniol caused cell cycle arrest in G0/G1 (10 μg/ml for 12 h, 10 and 200 μg/ml for 24 h) and G2/M (50 to 100 μg/ml for 12 and 24 h; 87 μg/ml for 72 h) phases. The L. sidoides also caused an arrest in G0/G1 with 100 μg/ml during 24 h and an arrest in G2/M with 100 and 150 μg/ml for 12 h and 150 μg/ml for 24 h. The L. salviifolia oil only induced stops in G2/M at a concentration of 150 μg/ml for 24 h, the oil of L. rotundifolia only stops in G0/G1 with 50, 100 and 200 μg/ml for 12 h and 50 μg/ml for 24 h. L. lacunose (50 μg/ml with 72 h of exposure) caused an arrest in G2/M. The L. alba geraniol and L. Lacunosa oils, in the 72h assay, caused an increase in fragmented DNA, but this did not reach levels as high as those observed for the MeWo cell line. Treatment of L. alba geraniol (200 μg/ml for 12 h) on MeWo and L. alba geraniol, L. lacunosa, L. rotundifolia and L. sidoides (100 μg/ml for 12 hours) on CT26.WT were subjected to analysis of differential expression of microRNAs by real-time PCR with a panel of 95 cancer-related microRNAs. All MeWo microRNAs showed downregulation compared to the negative control, which may have been due to the apoptotic effect of L. alba geraniol against this cell line. About CT26.WT 26 microRNAs for L. alba geraniol and L. lacunosa oils and 35 for L. rotundifolia and L. sidoides were found significantly desregulated (p<0.05) compared to control. The essential oils of tested Lippia species thus affected cell viability of MeWo and CT26.WT cell lines, indicating they might be good candidates as source of new anticancer biomolecules.