The medicinal and catalytic potential of model complexesnof vanadate-dependent haloperoxidases

Vanadium(V) complexes predominantly of composition VO(O3N), modeling the active center of vanadate-dependent haloperoxidases, are investigated with respect to (i) their catalytic potential in enantio-selective oxidation by peroxide of prochiral sulfides, and (ii) their in vitro cytotoxicity and insulin-mimetic ability towards fibroblast cell cultures. The peroxidation of methyl-tolylsulfide with cumyl-hydroperoxide, which is related to the sulfideperoxidase activity of haloperoxidases, is catalyzed by (RRR)-[VO(OMe)L] [H2L=(R,R)-bis(2-phenylethanol)-(R)-1-phenylethylamine] as well as by a mixture of [VO(OiPr)3] and H2L to an enantiomeric excess (ee) of 25%. The crystal and molecular structures of (RRR)-[VO(OMe)L] · 1/2MeOH are reported. In the context of the phosphatase activity of the apo-haloperoxidases, possible modes of action of vanadium compounds in insulin-mimesis are addressed. In vitro results for seven oxovanadium(IV) and -(V) coordination compounds show that, at essentially non-toxic concentrations [c(V)<0.1 mM], the compounds trigger glucose intake into human and simian virus modified mice fibroblasts, in several cases at a higher level than insulin