Synthesis, characterization, DNA binding properties and antioxidant activity of a manganese(II) complex with NO6 chromophore.

The mononuclear complex [Mn(thiophenyl-2-carboxylate)(2)(H(3)tea)] (1), where H(3)tea=triethanolamine has been synthesized, characterized, while the DNA binding properties and the antioxidant activity were studied. The crystal structure of 1 is also reported. The interaction between 1 and calf thymus double stranded (ds) DNA was electrochemically at a calf thymus DNA (CT-DNA) modified carbon paste electrode (CPE) and spectrophotometrically investigated, respectively. Adsorptive transfer stripping voltammetry showed that the interaction mode between 1 and CT-DNA depends on manganese(II) complex concentration. UV studies between 1 and CT-DNA revealed that 1 can bind to CT-DNA by the intercalative binding mode and the binding constant has been calculated. A competitive study with acridine orange (AO) showed that 1 exhibits the ability to displace the DNA-bound AO, since 1 binds to the DNA in competition with AO. In vitro antioxidant activity of free ligands and 1 was evaluated using five different antioxidant assays: a) interaction with 1, 1-diphenyl-2-picryl-hydrazyl (DPPH) stable free radical, b) the ΗΟ mediated oxidation of DMSO, c) scavenging of superoxide anion radicals, d) inhibition of lipid peroxidation and e) soybean lipoxygenase (LOX) inhibition. The results revealed the selectivity of the manganese complex to different free radicals as a consequence of its physicochemical feature. In particular, 1 presents significant inhibitory activity on LOX, with IC(50)=30 μM and selectivity to the inhibition of superoxide anion radicals and thus a promising candidate as a superoxide dismutase (SOD) biomimetic.