文摘
The present work was undertaken with an objective to investigate some biologically relevant attributes of peroxoniobium (pNb) derivatives, using a set of heteroleptic pNb compounds containing biogenic species as co-ligands. New peroxoniobium complexes corresponding to the general formula, Na2[Nb(O2)3L] (L = alanine or valine) were synthesized and comprehensively characterized by elemental analysis, IR, Raman, 13C NMR, 1H NMR, AAS and UV–Vis spectral studies, as well as thermogravimetric analysis. The structures of the compounds have been studied by density functional theory (DFT) method and their stability in solution at physiological pH has been ascertained. These compounds, along with our previously reported arginine and nicotinate complexes, Na2[Nb(O2)3(arg)]·2H2O and Na2[Nb(O2)3(nic)(H2O)]·H2O, respectively were screened for their activities with two different types of enzymes viz., catalase and acid phosphatase (ACP). Employing wheat thylakoid ACP as the model enzyme, it has been demonstrated for the first time that peroxoniobium derivatives serve as active inhibitors of phosphatase (IC50 values 2–9 μM). Enzyme kinetics data revealed that compounds exert mixed type of inhibition on ACP activity (Kii > Ki). Each of the tested pNb species exhibited significant resistance to degradation under the effect of catalase vis-a-vis the native substrate of the enzyme, H2O2.
