Abstract

In recent decades, research into finding new sources of secondary metabolites from marine ecosystems has been important. This interest is due to the natural products of marine origin to be structurally very diverse and complex, in many cases serve as a model and / or scaffold to manufacture new synthetic compounds (Newman and Cragg 2004, Koehn & Carter. 2005, Cragg & Newman 2013) In this study the cytotoxic effect of ethanol extracts and ethyl acetate, from the cell-free culture of a marine strain, isolated from the Antarctic marine sediments was assessed. This strain is in process of sequenciation. The sample was obtained from Punta Suffield (62 ° 12' S, 58 ° 55 'W) at 30m deep, and the cytotoxic effect was evaluated against Staphylococcus aureus, Candida albicans and human cancer cell lines. On S. aureus and C. albicans the minimum inhibitory concentration (MIC) was determined. On human tumor lines the median effective concentration (EC₅₀) for cellular viability was analysed using sulforhodamine B assay. Cell lines used were MCF-7 (breast cancer), PC-3 (prostate cancer), HT-29 (colon cancer) and CON (human colon epithelial cells), as a non-tumoral cell line control. Finally the selectivity index of each extract, corresponding ratio of the EC50 of non-tumor line (CON) with EC₅₀ of tumor cell line (MCF-7 cells, PC-3, HT29) was calculated. If the ratio is equal to or greater than 3, the extract, fraction or compound is considered selective. The ethanol extract had no greater effect against human pathogens used, with the minimum inhibitory concentration greater than 2.5 mg ml-¹ for both microorganisms. The effect of ethyl acetate extract on C. albicans was similar because the MIC was greater than 2.5 mg ml-¹. However, on S. aureus, the MIC was 500 µg ml-¹. In the four human cell lines both extracts were cytotoxic. Ethyl acetate extract was shown to be more effective, since the EC₅₀ into cells CON, MCF-7, PC-3, HT-29 were 61.03 µg ml-¹, 20.65 µg ml-¹, 61.29 µg ml- ¹ and 24.67 µg ml-¹ respectively. The EC₅₀ of ethanol extracts in the cells CON, MCF-7, PC-3 and HT-29 were 230.09 µg ml-¹, 174.58 µg ml-¹, 107.09 µg ml-¹ and 187.01 µg ml-¹ respectively. Regarding the selectivity index, both extracts are not selective in their action against tumor cells. The ethyl acetate extract was more selective than the ethanol extract as in MCF-7 (2.96) and HT-29 (2.47) cells observed values close to 3. The ethanol extract presented a selectivity index less than 2 in the three tumor cell lines. In conclusion, interesting cytotoxicity values were obtained, however it is necessary to isolate and identify bioactive metabolites to know the potential cytotoxicity of compound present in the extracts of the strain isolated from marine sediment of Antarctica.