Biospeciation of antidiabetic VO(IV) complexes

The possible transformations of antidiabetic vanadium(IV) complexes in the organism are discussed. These reactions involve absorption processes in the gastrointestinal tract, transport in the blood stream and interactions with endogenous binding molecules in the glucose-metabolizing cells. Modeling studies were mostly used to determine the actual chemical form of VO(IV) complexes in various biological environments. The results suggest that decomposition and subsequent ternary complex formation with endogenous or exogenous ligands in the organism affects the absorption efficacy of the originally neutral VO(IV) compounds considerably. During transport in the blood stream, transferrin displaces the carrier ligands from the VO(IV) compounds and plays an important role in transporting VO(IV) to the cell. In the cell, vanadium undergoes redox interaction with glutathione and complexation with adenosine 5'-triphosphate (the two important cell components present in mM concentration). In vitro and in vivo biological results confirmed some of the basic findings obtained from the modeling. (C) 2007 Elsevier B.V. All rights reserved.