Theoretical/experimental investigation and antimutagenic effect of the oxidovanadium(IV) baicalin coordination complex

Abstract

Vanadium is a transition metal with several oxidation states and some of these are represented in its biochemistry. The vanadium(IV) metal ion generally exists as oxidovanadium(IV) ion (VIVO2+) and forms stable complexes with a wide range of ligands. Flavonoids are a large group of polyphenolic compounds ubiquitouslypresent in plants that can coordinate and chelate metal ions due to the presence of oxo and hydroxyl groups. Baicalin is one of the main single active constituents isolated from the dried roots of S. baicalensis. We havepreviously synthesized and characterized the baicalin coordination complex with the oxidovanadium(IV) cation, Na4[VO(baic)2].6H2O (VIVO(baic)2). Unfortunately, suitable single crystals for X-ray diffraction determinationscould not be obtained. In the present work, we carried out a complete study of the geometrical, vibrational and electronic properties of this complex, and the knowledge of its biological properties was also extended. The penta-coordinated VIVO(baic)2 complex has a square pyramidal geometry. The theoretical IR spectrum showed reasonable agreement with the experimental FTIR spectrum. The frontier molecular orbitals (FMO) of the VIVO(baic)2 and [VO(apigenin)(H2O)2]Cl (VIVO(api)) complexes show significant differences. Nevertheless, the FMOon each complex show the same spatial arrangements than those of the free ligands. The VIVO(baic)2 complex shows no alkaline phosphatase inhibitory activity due to the low positive charge on the V]O group. Thiscomplex shows not only an adequate safety profile (without mutagenic action), but also an enhanced antimutagenic effect (protective effect) compared with the parental flavonoid.