DNA binding and cytotoxicity activity of a chiral iron(III) triangle complex based on a natural rosin product

The first chiral trinuclear iron(III) complex [Fe3(μ3-O)(L)6(CH3OH)2(CH3O)]⋅H2O (2) of a natural rosin product dehydroabietic acid (HL, 1) was synthesized and fully characterized. The interactions of 1 and 2 with salmon sperm DNA were investigated by viscosity measurements, UV, fluorescence and circular dichroism (CD) spectroscopic techniques. Absorption spectral (Kb=1.30×10(5)M(-1) (1), 1.40×10(5)M(-1)(2)), emission spectral (KSV=1.19×10(4)M(-1) (1), 1.79×10(4)M(-1) (2)) and viscosity measurements reveal that 1 and 2 interacted with DNA through intercalation and 2 exhibited a slight higher DNA binding ability. The Stern-Volmer quenching constant (KSV) and corresponding thermodynamic parameters (ΔG, ΔH and ΔS) of the binding processes were determined. The negative ΔH and ΔG values indicate that the binding reactions were exothermic and spontaneous. 1 and 2 were also screened for their cytotoxic ability and 1 demonstrated higher growth inhibition of the selected cancer cells at concentrations of 25μM and 50μM, this result was not identical with their DNA binding ability order. Thus, the involvement of Fe(III) centers had positive effect on DNA binding ability and negative effect on cytotoxicity.