Obtenção e avaliação da atividade tripanocida de novos complexos quadrático-planares de metais divalentes do grupo 10

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2020-05-26
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<span style="font-weight: 400;">Neste trabalho, três novos complexos de níquel (II), paládio (II) e platina (II) contendo os ligantes 5-hidroxi-3-metil-5-fenilpirazolina-1-(4-metil-3-tiosemicarbazona) (H<span style="font-weight: 400;">2<span style="font-weight: 400;">bmt) e trifenilfosfina (PPh<span style="font-weight: 400;">3<span style="font-weight: 400;">) foram sintetizados, com rendimentos satisfatórios, e caracterizados. As caracterizações dos complexos [Ni(bmt)PPh<span style="font-weight: 400;">3<span style="font-weight: 400;">] (1<span style="font-weight: 400;">), [Pd(bmt)PPh<span style="font-weight: 400;">3<span style="font-weight: 400;">] (2<span style="font-weight: 400;">) e [Pt(bmt)PPh<span style="font-weight: 400;">3<span style="font-weight: 400;">] (3<span style="font-weight: 400;">) foram feitas por meio de análise elementar, espectroscopia vibracional na região do infravermelho, espectroscopia de absorção na região do UV-Visível, RMN – <span style="font-weight: 400;">1<span style="font-weight: 400;">H, RMN – <span style="font-weight: 400;">13<span style="font-weight: 400;">C{<span style="font-weight: 400;">1<span style="font-weight: 400;">H}, RMN – <span style="font-weight: 400;">31<span style="font-weight: 400;">P{<span style="font-weight: 400;">1<span style="font-weight: 400;">H}, espectrometria de massas de alta resolução e difração de raios X por monocristal. As técnicas de caracterização confirmam que os complexos possuem as estruturas propostas, apresentando, portanto, geometria quadrática-planar, em que os centros metálicos estão coordenados pelos sítios doadores O, N<span style="font-weight: 400;">imina<span style="font-weight: 400;"> e S do ligante H<span style="font-weight: 400;">2<span style="font-weight: 400;">bmt, formando dois anéis quelatos, e pelo átomo de fósfofo do ligante PPh<span style="font-weight: 400;">3<span style="font-weight: 400;">. Os ensaios de atividade antiparasitária <span style="font-weight: 400;">in vitro<span style="font-weight: 400;"> contra a forma tripomastigota do protozoário <span style="font-weight: 400;">Trypanosoma cruzi<span style="font-weight: 400;"> (<span style="font-weight: 400;">T. cruzi<span style="font-weight: 400;">) mostraram que o complexo 1<span style="font-weight: 400;"> possui ação tripanocida e que a atividade biológica da tiossemicarbazona H<span style="font-weight: 400;">2<span style="font-weight: 400;">bmt é potencializada quando complexada com o Ni<span style="font-weight: 400;">II<span style="font-weight: 400;">. A complexação com o Pd<span style="font-weight: 400;">II<span style="font-weight: 400;"> e a Pt<span style="font-weight: 400;">II<span style="font-weight: 400;"> não provocou uma melhora na atividade tripanocida da H<span style="font-weight: 400;">2<span style="font-weight: 400;">bmt. Os ensaios de citotoxicidade dos complexos frente a macrófagos indicaram que os compostos possuem seletividade pela forma tripomastigota do <span style="font-weight: 400;">T. cruzi<span style="font-weight: 400;">. Ao se analisar os resultados dos ensaios biológicos, é possível verificar que a reatividade do centro metálico, possivelmente associada com a geometria molecular que o complexo apresenta, é um fator que modula a atividade tripanocida dos compostos descritos neste trabalho.  


<span style="font-weight: 400;">In this work, three novel nickel (II), palladium (II), and platinum (II) complexes containing the ligands 5-hydroxi-3-methyl-5-phenylpyrazoline-1-(4-methyl-3-thiosemicarbazone) (H<span style="font-weight: 400;">2<span style="font-weight: 400;">bmt) and triphenylphosphine (PPh<span style="font-weight: 400;">3<span style="font-weight: 400;">) were synthesized with satisfactory yields and characterized. The complexes [Ni(bmt)PPh<span style="font-weight: 400;">3<span style="font-weight: 400;">] (1<span style="font-weight: 400;">), [Pd(bmt)PPh<span style="font-weight: 400;">3<span style="font-weight: 400;">] (2<span style="font-weight: 400;">), and [Pt(bmt)PPh<span style="font-weight: 400;">3<span style="font-weight: 400;">] (3<span style="font-weight: 400;">) were characterized by elemental analysis, vibrational spectroscopy in the infrared region, absorption spectroscopy in the UV-Visible region, <span style="font-weight: 400;">1<span style="font-weight: 400;">H – NMR, <span style="font-weight: 400;">13<span style="font-weight: 400;">C{<span style="font-weight: 400;">1<span style="font-weight: 400;">H} – NMR, <span style="font-weight: 400;">31<span style="font-weight: 400;">P{<span style="font-weight: 400;">1<span style="font-weight: 400;">H} – NMR, high resolution mass spectrometry, and single crystal X ray diffraction. The characterization techniques confirmed the complexes have square-planar geometry, in which the metallic centers are coordinated by the O, N<span style="font-weight: 400;">imine<span style="font-weight: 400;">, and S donor sites of ligand H<span style="font-weight: 400;">2<span style="font-weight: 400;">bmt, forming two chelate rings, and by the phosphorus atom of ligand PPh<span style="font-weight: 400;">3<span style="font-weight: 400;">. The <span style="font-weight: 400;">in vitro<span style="font-weight: 400;"> biological assays with the trypomastigote form of the protozoa <span style="font-weight: 400;">Trypanosoma cruzi<span style="font-weight: 400;"> (<span style="font-weight: 400;">T. cruzi<span style="font-weight: 400;">) showed that complex 1<span style="font-weight: 400;"> exhibits trypanocidal activity and the complexation of H<span style="font-weight: 400;">2<span style="font-weight: 400;">bmt with Ni<span style="font-weight: 400;">II<span style="font-weight: 400;"> potentializes the thiosemicarbazone biological activity. The complexation with Pd<span style="font-weight: 400;">II<span style="font-weight: 400;"> and Pt<span style="font-weight: 400;">II<span style="font-weight: 400;"> resulted in no trypanocidal activity improvement for H<span style="font-weight: 400;">2<span style="font-weight: 400;">bmt. The cytotoxicity assays with macrophages indicated that the compounds are selective towards the trypomastigote form of <span style="font-weight: 400;">T. cruzi<span style="font-weight: 400;">. By analyzing the biological results, it is observed that the metallic center reactivity, possibly associated with the molecular geometry of the complex, modulates the trypanocidal activity of the compounds described in this work. 

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tiossemicarbazona, doença de Chagas, níquel (II), paládio (II), platina (II), thiosemicarbazone, platinum (II), palladium (II), nickel (II), Chagas disease
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