Abstract
The good chelating properties of hydroxypyrone (HPO) derivatives towards oxidovanadium(IV) cation, VIVO2+, constitute the precondition for the development of new insulin-mimetic and anticancer compounds. In the present work, we examined the VIVO2+ complex formation equilibria of two kojic acid (KA) derivatives, L4 and L9, structurally constituted by two kojic acid units linked in position 6 through methylene diamine and diethyl-ethylenediamine, respectively. These chemical systems have been characterized in solution by the combined use of various complementary techniques, as UV-vis spectrophotometry, potentiometry, NMR and EPR spectroscopy, ESI-MS spectrometry, and DFT calculations. The thermodynamic approach allowed proposing a chemical coordination model and the calculation of the complex formation constants. Both ligands L4 and L9 form 1:1 binuclear complexes at acidic and physiological pHs, with various protonation degrees in which two KA units coordinate each VIVO2+ ion. The joined use of different techniques allowed reaching a coherent vision of the complexation models of the two ligands toward oxidovanadium(IV) ion in aqueous solution. The high stability of the formed species and the binuclear structure may favor their biological action, and represent a good starting point toward the design of new pharmacologically active vanadium species.
Highlights
A number of studies have shown that vanadium compounds favor glucose intake into cells, lowering the level of glucose in blood; vanadium compounds, with respect to insulin, present the advantage of being orally active [8,9,10,11]
KAas a ligand of kojic acid (KA), a natural, non-toxic and low-cost product of large use in food derivatives, in which two KA units are linked in position 2 by diamines of different length; IV O2+ and the simple and cosmetic industries, their good chelating properties towards these ligands, depending on the length of the linker, form VIVO2+ complexes with various synthesis and constitute furtherdegree advantages
The complex formation equilibria were studied at 25 ◦ C and 0.1 M NaCl ionic strength by combined potentiometric-spectrophotometric titrations at 1:1, 1:2 and 1:4 VIV O2+ :ligand molar ratios with a constant ligand concentration of 3.0 × 10−4 M
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Vanadium compounds have emerged as useful anticancer agents because of desirable properties for chemotherapeutic reagents, displaying higher selectivity, low toxicity, greater reactivity, as well as anti-metastatic activity [16,17,18]. KAas a ligand of kojic acid (KA), a natural, non-toxic and low-cost product of large use in food derivatives, in which two KA units are linked in position 2 by diamines of different length; IV O2+ and the simple and cosmetic industries, their good chelating properties towards these ligands, depending on the length of the linker, form VIVO2+ complexes with various synthesis and constitute furtherdegree advantages. After the characterization of the systems in aqueous solution, biologicalmetal tests ions to 3+ , Al3+ , Cu2+ and Zn2+ ) has been already studied; in the case of the hard Fe3+ metal After the characterization of the systems in aqueous solution, biological tests to evaluate the antidiabetic and cytotoxic potential of these vanadium complexes will be carried out in a research step
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