Structural effects on the hesperidin properties obtained by chelation to magnesium complexes

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, 1H 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 ± 3.05 μg mL− 1) and liposoluble (log P = − 0.15 ± 0.01) than free hesperidin (S = 5.92 ± 0.49 μg mL− 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 = 68.3 μM at pH 7.8) than free hesperidin (IC50 = 116.68 μmol L− 1) and vitamin C (IC50 = 852 μmol L− 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.

Graphical abstractThis work demonstrates that chelation of hesperidin (hesp) to {Mg(phen)}2 +moiety, where phen is 1,10′-phenanthroline, results in the formation of the new luminescent complex [Mg(hesp)2(phen)], which presents structural features, which are essential to improve the physico-chemical and antioxidant activity of the hesperidin in the physiologic medium.Figure optionsDownload full-size imageDownload as PowerPoint slide