Synthesis and Cytoprotective Properties of La(III), Ce(III) Complexes Possessing 2,6-Di-tert-butylphenol Moiety

Novel complexes of lanthanum and cerium possessing antioxidant 2,6-di-tert-butylphenol moiety have been synthesized and characterized using NMR, IR spectroscopy, thermogravimetry and elemental analysis. Their redox properties have been investigated using cyclic voltammetry. Antioxidant activity has been evaluated in a series of model reactions in vitro. The affinity of the compounds for single electron transfer has been estimated in the CUPRAC test, while their radical scavenging capacity has been monitored in the DPPH test and their interaction with the superoxide radical anion has been investigated in the NBT test. It has been demonstrated that both complexes exhibit extraordinary antioxidant activity far surpassing that of known standards. The cerium complex appears to be 20 times more effective at scavenging superoxide radical anions than its lanthanum counterpart, which may be due to the unique +4 oxidation state of cerium. Biological activity has also been estimated in numerous in vitro assays. The ability of the complexes to inhibit lipoxygenase LOX-1B has been observed in a corresponding assay, showing mild inhibitory activity for both compounds. Cytotoxicity was evaluated using the common MTT assay, and the cytoprotective properties of the compounds were investigated using clonogenic analysis. Both compounds were found to be non-toxic at operating concentrations, and the cerium complex showed cytoprotective activity at radiation doses of about 2 Gy. These findings suggest that the synthesized complexes have the potential to be effective antioxidants and low-toxic cytoprotectors.