title: Behavior of the potential antitumor V(IV)O complexes formed by flavonoid ligands. 1. Coordination modes and geometry in solution and at the physiological pH.
abstract: The coordination modes and geometry assumed in solution by the potent antitumor oxidovanadium(IV) complexes formed by different flavonoids were studied by spectroscopic (Electron Paramagnetic Resonance, EPR) and computational (Density Functional Theory, DFT) methods. A series of bidentate flavonoid ligands (L) with increasing structural complexity was examined, which can involve (CO, O(-)) donors and formation of five- and six-membered chelate rings, or (O(-), O(-)) donors and five-membered chelate rings. The geometry corresponding to these coordination modes can be penta-coordinated, [VOL2], or cis-octahedral, cis-[VOL2(H2O)]. The results show that, at physiological pH, ligands provided with (CO, O(-)) donor set yield cis-octahedral species with "maltol-like" coordination when five-membered chelate rings are formed (as with 3-hydroxyflavone), while penta-coordinated structures with "acetylacetone-like" coordination are preferred when the chelate rings are six-membered (as with chrysin). When both the binding modes are possible, as with morin, the "acetylacetone-like" coordination is observed. For the ligands containing a catecholic donor set, such as 7,8-dihydroxyflavone, baicalein, fisetin, quercetin and rutin, the formation of square pyramidal complexes with (O(-), O(-)) "catechol-like" coordination and five-membered chelate rings is preferred at physiological pH. The determination of the different coordination modes and geometry is important to define the biotransformation in the blood and the interaction of these complexes with the biological membranes.
authors.affiliation: Istituto CNR di Chimica Biomolecolare, Trav. La Crucca 3, I-07040 Sassari, Italy.
authors.forename: Daniele
authors.initials: D
authors.lastname: Sanna
authors.affiliation: Dipartimento di Chimica e Farmacia, Università di Sassari, Via Vienna 2, I-07100 Sassari, Italy.
authors.forename: Valeria
authors.initials: V
authors.lastname: Ugone
authors.affiliation: Dipartimento di Chimica e Farmacia, Università di Sassari, Via Vienna 2, I-07100 Sassari, Italy.
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Lubinu
authors.affiliation: Dipartimento di Chimica e Farmacia, and Centro Interdisciplinare per lo Sviluppo della Ricerca Biotecnologica e per lo Studio della Biodiversità della Sardegna, Università di Sassari, Via Vienna 2, I-07100 Sassari, Italy.
authors.forename: Giovanni
authors.initials: G
authors.lastname: Micera
authors.affiliation: Dipartimento di Chimica e Farmacia, and Centro Interdisciplinare per lo Sviluppo della Ricerca Biotecnologica e per lo Studio della Biodiversità della Sardegna, Università di Sassari, Via Vienna 2, I-07100 Sassari, Italy. Electronic address: garribba@uniss.it.
authors.forename: Eugenio
authors.initials: E
authors.lastname: Garribba
mesh_terms: D000970:Antineoplastic Agents / Q000737:chemistry*; D004578:Electron Spin Resonance Spectroscopy; D005419:Flavonoids / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D008024:Ligands; D010087:Oxides / Q000737:chemistry; D012996:Solutions; D017968:Vanadium Compounds / Q000737:chemistry*
chemical_list: D000970:Antineoplastic Agents; D005419:Flavonoids; D008024:Ligands; D010087:Oxides; D012996:Solutions; D017968:Vanadium Compounds
keywords: Density functional theory calculations; EPR spectroscopy; Vanadium