Chromium(III)-isocinchomeronato and quinolinato complexes: kinetic studies in NaOH solutions and effect on 3T3 fibroblast proliferation

Abstract

The aquation of chromium(III)-isocinchomeronato and quinolinato complexes, mer-[Cr(icaH) 3 ] 0 and mer-[Cr(quinH) 3 ] 0 (where icaH -and quinH -are N,Obonded isocinchomeronic and quinolinic acid anion, respectively) was studied in NaOH solutions. The process leads to successive ligand liberation in the fully deprotonated species. The kinetics of the first ligand liberation were studied spectrophotometrically in the visible region. A mechanism is proposed in which the rate of the chelatering opening at the Cr-N bond is much faster than the rate of the Cr-O bond breaking. The rate-determining step is described by the rate law:where k OH(1) and k O are rate constants of the first ligand liberation from the hydroxo-and oxo-forms of the intermediate, respectively, and Q 2 is an equilibrium constant between these two protolytic forms. The first pseudo-firstorder rate constants (k obs1 ) were calculated using SPECFIT software for an A ? B ? C reaction pattern. The results are compared with those determined in acidic medium. Kinetics of the second and third ligand liberation were also studied and values of successive pseudo-first-order rate constants (k obs2 , k obs3 ) are [OH -] independent. Effect of chromium(III)-quinolinato and isocinchomeronato complexes on 3T3 fibroblast proliferation was evaluated. Cytotoxicity of these complexes is low, suggesting they may be promising candidates as novel dietary supplements.

Chromium(III) complexes with lutidinic acid: kinetic studies in HClO4 and NaOH solutions

“…C reaction pattern. However, only the first ligand dissociation is well characterized because the second reaction step is obscured by the further processes [7,25]. For that reason, the k obs2 values can serve only as qualitative data.…”

“…C, where A = tris-, B = bis-, C = mono-lut complex. However, due to the ageing process of chromates(III) [7,25] only the first reaction step is well characterized by the k obs1 values.…”

“…It seems that pyridinedicarboxylic acids, able to form picolinato-type complexes, could be better chromium transporters. Recently, chromium(III) complexes with quinolinic and isocinchomeronic acids were characterized in acidic and alkaline media [5][6][7] and their cytotoxicity towards 3T3 fibroblast cells was established [7]. The results demonstrated that these complexes are promising candidates as novel dietary supplements.…”

Kinetic studies on chromium-glycinato complexes in acidic and alkaline media

“…Previously, series of complexes with pyridinemonocarboxylato and pyridinedicarboxylato ligands were obtained and kinetic studies on their acid-and base-catalysed aquation were performed [e.g. [6][7][8][9][10]. Additional studies on their effect toward 3T3 fibroblasts revealed that they are not toxic and may be good candidates as biochromium sources [6,10].…”

“…[6][7][8][9][10]. Additional studies on their effect toward 3T3 fibroblasts revealed that they are not toxic and may be good candidates as biochromium sources [6,10]. On the other hand, it is likely that a higher bioavailability characterizes chromium(III) complexes with amino acids, as naturally existing biomolecules.…”