Glucose-lowering properties of vanadium compounds: Comparison of coordination complexes with maltol or kojic acid as ligands

Bis(kojato)oxovanadium(IV) [abbreviated VO(ka)(2)], a close chemical analog of the insulin-mimetic lead compound bis(maltolato) oxovanadium (IV) - abbreviated BMOV or VO(ma)(2) - is reported and its reaction chemistry and insulin-mimetic properties are presented. VO(ka)(2) [log K-1 = 7.61(10), log K-2 = 6.89(6), log beta(2) = 14.50(16)] has a reaction chemistry which directly parallels that of VO(ma)(2). In aqueous solution it is more slowly oxidized by molecular oxygen to [VO2(ka)(2)](-) than is VO(ma)(2) to [VO2(ma)(2)](-). Variable pH electrochemistry and variable pH V-51 NMR of solutions of VO(Ka)(2) are presented and contrasted with the corresponding results for VO(ma)(2). Time course studies (24 hr) in Sn-diabetic rats following the oral or ip administration of VO(ka)(2), VO(ma)(2), VO2+ (vanadyl) as vanadyl sulfate (VOSO4), and [VO2(ma)(2)](-) as its [NH4](+) salt have been performed, as have chronic oral studies comparing VO(ka)(2) and VO(ma)(2) over a six week period. lit all studies, the most potent form of vanadium was the neutrally charged water soluble, complex VO(ma)(2). (C) 1997 Elsevier Science Inc.