SOD activity of new copper II complexes with ligands derived from pyridoxal and toxicity in Caenorhabditis elegans.

This work presents the synthesis, characterization of copper(II) complexes (C1-C6) and the potential of these compounds to mimic the catalytic activity of the enzyme superoxide dismutase (SOD). The copper(II)complexes were obtained by reaction between the aldol condensation between substituted aromatic hydrazides and aromatic aldehydes (salicylic aldehyde and pyridoxal hydrochloride), forming two new ligands (L1 to L6), resulting in new dimeric dicopper (II) complexes (C1 and C2), new three monomeric CuII derivatives (C3, C4 and C6) and a polymeric complex (C5). The CuII complexes were fully characterized by X-ray diffraction, spectroscopic and electrochemical analysis. Subsequently, CuII derivatives were evaluated for their antioxidant activities, using the NBT (Nitro blue tetrazolium chloride) photoreduction methodology. After evaluating the antioxidant activity in vitro, it was observed that the best inhibition rates of the superoxide ion are associated to the C4 and C5 complexes. Computational analysis via molecular docking and quantum chemical calculation (Fukui map) offered a molecular level explanation on the biological activity of CuII complexes. Additionally, cytotoxicity of C1-C6 was tested in the first time in vivo in nematodes Caenorhabditis elegans, corroborating with the results identified for C4 and C5.