Chemical compounds from skin secretions from toads of Bufonidae family have been long-studied. In the search for new molecules with pharmacological action, the 3β-OH groups of bufadienolides are ...commonly derivatised using acetyl groups. This work described the isolation and/or structural elucidation of isolated and derivatised compounds from the venom of the Brazilian anuran Rhinella marina, and their evaluation in in vitro assays. In the methanolic extract of the R. marina venom, compound cholesterol (1) was isolated from the CRV-52 fraction by classic column chromatography, dehydrobufotenine (2) by Sephadex LH-20 from the CRV-28 fraction, and a mix of suberoyl arginine (3) and compound 2 was obtained from the CRV-6-33 fraction. The compounds marinobufagin (4), telocionbufagin (5) and bufalin (6) were isolated by classic column chromatography, followed by separation via HPLC in the CRV-70 fraction, and the compound marinobufotoxin (9) was isolated by classic column chromatography in the CRV-6 fraction, here being isolated for the first time in R. marina specimens. Compounds 4 and 5 were submitted for acetylation with acetic anhydride, in the presence of pyridine and 4-dimethyilaminopiridine (DMAP), in order to obtain the compounds 3-acetyl-marinobufagin (7) and 3-acetyl-telocinobufogin (8). The isolated and derivatised compounds were identified by 1H and 13C NMR, and their molecular mass confirmed by mass spectrometry. All compounds (except 1 and 3) were tested in cytotoxic assays by the MTT method and presented cytotoxic potential against human cancer cell lines, as well as against non-tumoral human embryonic kidney HEK-293 cells. With the exception of compound 2, all molecules presented IC50 values < 4 μM, and none caused hemolysis of human erythrocytes, demonstrating a promising cytotoxic potential of natural and chemically-modified bufadienolides. This study presents a detailed contribution of bioactive chemicals from Brazilian Amazon Rhinella species, and indicates promising areas for further studies and pharmaceutical investments.
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•Seven compounds were identified in the extract from Rhinella marina venom.•Compounds 4 and 5 were acetylated resulting in the compounds 7 and 8.•Marinobufotoxin (9) was isolated for the first time in Rhinella marina.•The tested compounds demonstrated potent activity against tumour cell lines.
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•Marinobufagin has high antiproliferative activity on human tumor lines only.•HL-60 cells displayed binucleation, cellular and nuclear condensation and cytoplasmic ...vacuoles.•Marinobufagin increased the apoptotic status, caused DNA fragmentation and phosphatidylserine externalization in HL-60 cells.•Marinobufagin caused mitotic index reduction, cell cycle arrest and chromosomal alterations in divinding Allium cepa meristems.
Skin toad secretion present physiologically active molecules to protect them against microorganisms, predators and infections. This work detailed the antiproliferative action of marinobufagin on tumor and normal lines, investigate its mechanism on HL-60 leukemia cells and its toxic effects on Allium cepa meristematic cells. Initially, cytotoxic action was assessed by colorimetric assays. Next, HL-60 cells were analyzed by morphological and flow cytometry techniques and growing A. cepa roots were examined after 72 h exposure. Marinobufagin presented high antiproliferative action against all human tumor lines IC50 values ranging from 0.15 (leukemia) to 7.35 (larynx) μM and it failed against human erythrocytes and murine lines. Human normal peripheral blood mononuclear cells (PBMC) were up to 72.5-fold less sensitive IC50: 10.88 μM to marinobufagin than HL-60 line, but DNA strand breaks were no detected. Leukemia treaded cells exhibited cell viability reduction, DNA fragmentation, phosphatidylserine externalization, binucleation, nuclear condensation and cytoplasmic vacuoles. Marinobufagin also reduced the growth of A. cepa roots (EC50: 7.5 μM) and mitotic index, caused cell cycle arrest and chromosomal alterations (micronuclei, delays and C-metaphases) in meristematic cells. So, to find out partially targeted natural molecules on human leukemia cells, like marinobufagin, is an amazing and stimulating way to continue the battle against cancer.
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•A novel series of nine quinoxalinyl-hydrazones was synthesized and characterized.•(E)-2-2-(2-Pyridin-2-ylmethylene)hydrazinylquinoxaline (PJOV56) showed strong cytotoxic activity ...against a panel of human tumor-derived cancer cell lines.•PJOV56 exhibited antiproliferative activity against HCT116 cells suppressing cell growth in the time- and dose-dependent manner.•Low concentrations (1.5 and 3.0 µmol.L−1) of PJOV56 induced cell cycle arrest in S-phase without apparent cell death in HCT116 cells.•High concentration (6.0 µmol.L−1) of PJOV56 led to a cell cycle arrest in G0/G1-phase and to a significant level of apoptotic cell death in HCT116 cells.•PJOV56 induced intense vacuolization in HCT116 cells that ressemble autophagic process induction.
Quinoxaline derivatives are reported as antineoplastic agents against a variety of human cancer cell lines, with some compounds being submitted to clinical trials. In this work, we report the synthesis, characterization and cytotoxicity potential of a new series of quinoxalinyl-hydrazones. The most cytotoxic compound was (E)-2-2-(2-pyridin-2-ylmethylene)hydrazinylquinoxaline (PJOV56) that presented a time-dependent effect against HCT-116 cells. After 48 h of incubation, PJOV56 was able to induce autophagy and apoptosis of HCT-116 cells, mediated by upregulation of Beclin 1, upregulation of LC3A/B II and activation of caspase 7. Apoptosis was induced along with G0/G1 cell cycle arrest at the highest concentration of PJOV56 (6.0 µM). Thus, PJOV56 showed a dose-dependent mode of action related to induction of autophagy and apoptosis in HCT-116 cells.
