Resumo

Cyanobacteria produce numerous and structurally diverse secondary metabolites, in particular non-ribosomal peptides and polyketides that may prove useful for the development of novel drugs, which include bioactive compounds with cytotoxic, antifungal, antiviral, anticancer, antimitotic, antimicrobial, antitumor, specific enzyme inhibition and immunosuppressive activities. This study reports on the evaluation of cyanobacteria for their anticancer activity. Ten cyanobacterial strains were chosen for this screening, which include Nostoc sp. CENA67, CENA68, CENA69, Microcystis aeruginosa NPCD-1, NPLJ-4, SPC777, M. panniformis SPC702, Sphaerocavum brasiliense SPC484, Cylindrospermopsis raciborskii 339-T3 and Brasilonema terrestre CENA116. The extracts of these ten strains were prepared using dichloromethane and ethanol, successively, and screened for in vitro anticancer activity against a panel of seven human cancer cell lines (U251 glioma, central nervous system; NCI-ADR/RES, ovary, phenotype of the multidrug resistance; 786-0, kidney; NCI-H460, lung non-small cell type; PC-3, prostate; HT29, colon; K562, leukemia) and one non-tumoral cell line (3T3, murine embryonal fibroblast). The antiproliferative results were expressed as GI₅₀ (concentration that produced 50% of growth inhibition) and were classified into four categories according to the average activity as inactive (mean logGI₅₀ > 1.5 µg/mL), weak activity (1.5 ≤ mean logGI₅₀ < 1.10 µg/mL), moderate activity (1.1 < mean logGI₅₀ < 0 µg/mL) and potent activity (mean logGI₅₀ < 0 µg/mL). The dichloromethane extract of B. terrestre CENA116 and the ethanolic extract of Nostoc sp. CENA69 showed weak activity against a panel of seven human cancer cell lines, while the dichloromethane extract of Nostoc sp. CENA69 showed moderate activity. Mass spectrometry (MS) analysis was performed in order to verify the cyanopeptides profile. Most of compounds identified by MS analysis belong to protease inhibitors class. The results showed antiproliferative potential of cyanobacterial extracts.