A glutathione peroxidase mimic 6,6′-ditellurobis (6-deoxy-β- cyclodextrin) with high substrate specificity

Glutathione peroxidase (GPx) is one of the most important antioxidative selenoenzymes in living organisms. The novel GPx mimic 6,6′- ditellurobis(6-deoxy-β-cyclodextrin) (6-TeCD) was prepared and evaluated for its capacity to catalyze the reduction of H₂O₂, tert-butyl hydroperoxide (t-BuOOH), and cumene hydroperoxide (CuOOH) by glutathione (GSH) or 3-carboxy-4-nitrobenzenethiol (ArSH). Compared the ArSH assay with the coupled reductase assay, we found that 6-TeCD exhibited strong substrate specificity for aromatic thiol substrate. The specificity led to efficient peroxidase activity almost 100,000-fold than that for a well-known GPx mimic diphenyl diselenide (PhSeSePh). Furthermore, reduction of lipophilic CuOOH was proceeded ca. 30 times faster than the more hydrophilic H ₂O₂, which cannot bind into the hydrophobic cavity of β-cyclodextrin. Thus, it seemed that catalytic activity of cyclodextrin-derived GPx models strongly depends on the structurally different both substrates hydroperoxides (ROOH) and thiols.