title: Structural effects on the hesperidin properties obtained by chelation to magnesium complexes.
abstract: The magnesium complex [Mg(hesp)2(phen)] (1), where hesp=hesperidin and phen=1,10'-phenanthroline, was synthesized and characterized by Elemental Analysis (C,H,N), atomic absorption and spectroscopic (FTIR, UV-visible, (1)H NMR) techniques. The congested structure facilitates the tilting and contact of the two hesperidin ligands by hydrogen bonding interactions having a stabilizer effect on the hesperidin. The hydrogen bonds are strongly affected by the solvent used which can lead to changes in the physical-chemical, luminescence and biologic properties of complex 1. Complex 1 is more hydrosoluble (S=472±3.05μgmL(-1)) and liposoluble (log P=-0.15±0.01) than free hesperidin (S=5.92±0.49μgmL(-1), log P=0.30). Oxidation of the complex in an aqueous solution and room temperature investigated by cyclic voltammetry resulted in a very stable two-electron cyclic process to form the phenoxonium neutral, cation and dication radicals. The stability of the voltammetric process indicates that the species produced are never exhausted and does not lead to changes in the coordination sphere composition. The complex was found to be a better radical scavenger for superoxide radical (IC50=68.3μM at pH7.8) than free hesperidin (IC50=116.68μmolL(-1)) and vitamin C (IC50=852μmolL(-1)). The strong blue fluorescence of complex 1 switches through loss of luminescence in pure water/protic organic solvents or when protected from water (in octanol for example as a model of phospholipid membranes). These features provide an opportunity to map the reactivity of hesperidin in the physiologic medium. In this context, a high uptake of complex into HeLa cells was detected by fluorescence microscopy. The blue fluorescence was uniformly distributed mainly in per nucleic region.
authors.affiliation: Departamento de Química, Universidade Federal de São Carlos, Rodovia Washington Luís, Km 235 CP 676, CEP 13565-905 São Carlos, SP, Brazil.
authors.forename: Regina M M
authors.initials: RM
authors.lastname: Oliveira
authors.forename: Juliana F
authors.initials: JF
authors.lastname: de Souza Daniel
authors.forename: Inara
authors.initials: I
authors.lastname: de Aguiar
authors.forename: Maria Fátima
authors.initials: MF
authors.lastname: das Graças Fernandes Silva
authors.forename: João
authors.initials: J
authors.lastname: Batista Fernandes
authors.forename: Rose M
authors.initials: RM
authors.lastname: Carlos
mesh_terms: D002467:Cell Nucleus / Q000378:metabolism; D016166:Free Radical Scavengers / Q000138:chemical synthesis* / Q000737:chemistry* / Q000494:pharmacology; D006367:HeLa Cells; D006569:Hesperidin / Q000138:chemical synthesis* / Q000737:chemistry* / Q000494:pharmacology; D006801:Humans; D008274:Magnesium / Q000737:chemistry*; D013481:Superoxides / Q000737:chemistry* / Q000378:metabolism
chemical_list: D016166:Free Radical Scavengers; D013481:Superoxides; D006569:Hesperidin; D008274:Magnesium
keywords: Antioxidant activity; Biologic properties; Flavonoids; Luminescence; Magnesium(II) complex