Novos complexos de Ru(II) e Mg(II) com flavonóides : atividade tóxica, sítios ativos e mecanismos de ação
Oliveira, Regina Maria Mendes
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The use of pesticides in agriculture, in order to enhance and ensure food production for a growing population has led to many concerns about risks to human health and the environment. Therefore, search for new strategies which seek a safer alternative is very important. With this aim, herein we describe new ruthenium(II) and magnesium(II) complexes containing phenanthroline and flavonoids (hesperidin, hesperetin, naringin or naringenin) ligand, These complexes were synthesized and characterized by elemental analysis (C,H,N), atomic absorption and ESI-MS(+). The structures were investigated by computational calculation and 1H, 13C NMR spectroscopic techniques. The complexes are stable in solid state, in most of the organic solvents tested and at various pH values. They are more hydrosoluble and liposoluble than the free flavonoides. The insecticidal activity bioassay against the leafcutting ants Atta sexdens rubropilosa demonstrated that the complexes show a delayed kill action. The activity of the Electrophorus electricus AChE enzyme was moderately inhibited by the Ru2+ complexes whereas the Mg2+ complexes were powerfull inhibitors only against AChE of Atta sexdens rubropilosa, indicating their high selectivity to insects. Further, the complexes are essentially non-toxic to the aquatic bacterium Vibrio fischeri and to human HeLa cells. The Mg2+ complexes presented unique properties: (i) in the electrochemical experiments in aqueous solution was observed the formation of a cyclic mechanism stable involving neutral, ionic and radical species; (ii) are better scavenger superoxide radical than the free flavonóides; (iii) presents a strong blue fluorescence. They act as an on/off fluorescent switch through the changing of the medium, solvents and pH. The fluorescence observed by confocal microscopy allowed to detect the high absorption of the magnesium complexes in the HeLa cells. Overall, the physicochemical and biological properties observed for Ru2+ and Mg2+ complexes opens new frontiers of application for these compounds in various areas of science such as agriculture, medicine, and optical materials.