The complexes Diaqua-bis(5-nitroimidazole)-copper(II)-dinitrate (1); Tetrakis(4-phenylimidazole)-copper(II)-dinitrate, ethanol solvate (2); Bis(4-phenylimidazole)-bis(acetate)-copper(II) (3); Hexakis(4-phenylimidazole)-cobalt(II)-acetate (4) and Bis(2-phenylimidazole)-bis(acetate)-cobalt(II) (5), have been synthesized. Their structures were determined by X-ray analysis.The antimicrobial activities of these complexes have been screened in vitro against the microorganisms Escherichia coli, Klebsiella pneumoniae, Shigella flexneri, Salmonella typhi, Salmonella enteritidis, Salmonella enterica, Staphylococcus aureus, Listeria monocytogenes. Complexes (1) and (3) showed antimicrobial activity over Gram positive and negative bacteria by a bacteriostatic effect. On the other hand, complexes (4) and (5) showed antibacterial activity with a bacteriolytic effect over Gram positive and negative bacteria.The cytotoxicity of complexes (3) and (4) was tested in vitro. These complexes presented cytotoxic effect to values near the MIC.

The preparation, magnetic characterization and antimicrobial properties of the complexes [Fe 3 O) (2), where MeImid is 2-methyl-imidazolium and BPA is 2,2´-bipyridine, are described.The variable temperature susceptibilities of these complexes were investigated in the temperature range 2-300K. The data have been modeled on the assumption of "butterfly" arranged for (2) and equilateral triangle of ferric ions for (1).The antimicrobial activities of these complexes have been screened in vitro against different bacterial strains. The complexes (1) and (2) display activity over Gram negative bacteria and these compounds not present activity over Gram positive strains. These complexes have bacteriostatic effect over bacterial target. The toxicity analyses of iron complexes showed these have cytotoxicity effect to values around the MIC on human cell.

RESUMEN:Las bacteriocinas son péptidos antimicrobianos de síntesis ribosomal secretadas por bacterias. Dentro de estas destaca nisina que posee potenciales usos en terapias antibióticas, como biopreservante de alimentos y probióticos. También se ha descrito que nisina posee citotoxicidad sobre líneas celulares neoplásicas, pero existe poca información de su efecto sobre células tumorales sanguíneas. Debido al potencial uso que presenta nisina, es relevante determinar la toxicidad que presenta sobre líneas celulares tumorales del tipo sanguíneo. Para esto, se realizaron ensayos de actividad hemolítica sobre eritrocitos humanos y de toxicidad sobre células mononucleares de sangre periférica humanas, determinándose que nisina no posee efecto citotóxico sobre este tipo de células normales humanas sanguíneas. Se realizaron también, ensayos de citotoxicidad con líneas celulares tumorales (K562 y U937), con el fin de determinar dosis, tiempo de exposición y selectividad en el efecto tóxico de nisina sobre las células tumorales humanas. Estos ensayos muestran que nisina presenta actividad citotóxica sobre líneas celulares K562 y U937 a las 72 h de exposición, a una concentración de 40 µg/mL, que corresponde a 100 veces la concentración mínima inhibitoria (MIC) usada para su acción sobre bacterias. Al comparar el efecto de nisina sobre células mononucleares de sangre periférica humanas con las líneas tumorales linfoides y mieloides (K562 y U937 respectivamente), se observa un efecto selectivo de nisina sobre las células tumorales sanguíneas.

Cancer is the second leading cause of death in the world and colorectal cancer is the only cancer that has shown a sustained increase in mortality in the last decade. In the search for new chemotherapeutic agents against cancer, extremophilic microorganisms have shown to be a potential source to obtain molecules of natural origin and with selective cytotoxic action towards cancer cells. In this work we analyzed the ability of a collection of Antarctic soil bacteria, isolated on Collins Glacier from the rhizosphere of Deschampsia antarctica Desv plant, to secrete molecules capable of inhibiting cell proliferation of a colorectal cancer tumor line. Our results demonstrated that culture supernatants from the Antarctic bacteria K2I17 and MI12 decreased the viability of LoVo cells, a colorectal adenocarcinoma cell line. Phenotypic and genotypic characterization of the Antarctic bacteria showed that they were taxonomically related and nucleotide identity analysis based on the 16S rRNA gene sequence identified the bacterium K2I17 as a species belonging to the genus Bacillus.