Estudo do potencial antineoplásico da biflorina, о- naftoquinona isolada das raízes de Capraria biflora L

• Ano de defesa: 2007
• Autor(a) principal: Vasconcellos, Marne Carvalho de
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: por
• Palavras-chave em Português: Farmacologia; Ensaios de Seleção de Medicamentos Antitumorais
• Link de acesso: http://www.repositorio.ufc.br/handle/riufc/3726

Biflorin is a 1,4 - o-naftoquinone isolated from the roots of Capraria biflora, which has an ample distribution among North and South América. The goal of this study was to evaluate the antitneoplastic potential of biflorine in vitro and in vivo models. Genotoxic effects in human peripheral lymphocytes and other cell models, such as V79, bacteria and yeasts, as well as in mice bone marrow. Was also accessed biflorin was highly cytotoxic against 15 human tumor cell lines and 1 murine cell line, with IC50 ranging from 0.43 to 14.61 µg/mL. Cell selectivity was was not observed, since in was equally toxic to normal human lymphocytes stimulated with phytoheamaglutinin. No inhibitory effect on see-urchin egg development or lysis of mouse erythrocyte was observed following biflorin treatment. Mode of action studies and antitumor potential was evaluated on the B16 melanoma cell line, which enables in vitro and in vivo studies. The in vitro data suggests that biflorin induces cell death by apoptosis, as treated cells showed a decrease in nucleus size, chromatin condensation and formation of apoptotic bodies. Flow cytometry confirmed DNA fragmentation and a significant mitochondrial depolarization on the highest concentration tested. Membrane integrity disruption was not observed when analyzed by flow cytometry and no increase in non viable cells was registered. The later result was also seen on the trypan blue exclusion cell count. In vivo antitumor activity was evaluated in three tumor models: Sarcoma 180, Erlich´s Carcinoma and Melanoma B16. Biflorin inhibited tumor growth in S-180 and Erlich transplanted animals and increased the antitumor effect of 5-FU where decreasing its toxicity. On B16 transplanted animals, survival span of biflorin-treated animals increased significantly. It was demonstrated that biflorin possess immune-adjuvant proprieties, increasing the production of anti-albumin antibodies, which can be related to its antitumor activity. Interaction of biflorin with single and double stranded DNA was confirmed, but was shown that it does not inhibit topoisomerase I, suggesting that a different mechanism is associated with this interaction, probably DNA damage induction. Biflorin showed genotocicity only on the comet assay, in which frequency and damage index towards human lymphocytes were significantly increased, without, however, inducing clastogenic effect on chromosome aberration assessment. On the other hand, due to its antioxidant effect, possibly associated to removal of hydroxi groups, biflorin, in lower concentrations, showed antimutagenic activity towards V79 cells and Saccharomyces cereviseae treated with H2O2. Moreover, it does not induce lipidic peroxidation, thus reducing this effect in V79 cells, as seen by assessment of TBARS levels. To discard any doubts on biflorin´s non-mutagenic proprieties; the Ames test in Salmonella thyphimurium and the micronucleus assay on mouse bone marrow was carried out, both presenting a negative result. Taken together, these results suggest that biflorin is a strong cytotoxic compound against neoplastic cells as possess antitumor, immune-adjuvant and antioxidant potential, interacts directly with single and double stranded DNA, but not topoisomerase I, has a genotoxic but not mutagenic effect and increases survival rate in treated mice