Synthesis, DNA‐Binding, Cleavage, and Cytotoxic Activity of New 1,7‐Dioxa‐4,10‐diazacyclododecane Artificial Receptors Containing Bisguanidinoethyl or Diaminoethyl Double Side Arms

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Abstract
Novel 1,7‐dioxa‐4,10‐diazacyclododecane artificial receptors with two pendant aminoethyl (3) or guanidinoethyl (4) side arms have been synthesized. Spectroscopy, including fluorescence and CD spectroscopy, of the interactions of 3, 4, and their copper(II) complexes with calf thymus DNA indicated that the DNA binding affinity of these compounds follows the order Cu2+–4>Cu2+–3>4>3, and the binding constants of Cu2+–3 are Cu2+–4 are 7.2×104 and 8.7×104 M−1, respectively. Assessment by agarose gel electrophoresis of the plasmid pUC 19 DNA cleavage activity in the presence of the receptors showed that the complexes Cu2+–3 and Cu2+–4 exhibit powerful supercoiled DNA cleavage efficiency. Kinetic data of DNA cleavage promoted by Cu2+–3 and Cu2+–4 under physiological conditions fit to a saturation kinetic profile with kmax values of 0.865 and 0.596 h−1, respectively, which give about 108‐fold rate acceleration over uncatalyzed supercoiled DNA. This acceleration is due to efficient cooperative catalysis of the copper(II) center and the functional (diamino or bisguanidinium) groups. In‐vitro cytotoxic activities toward murine melanoma B16 cells and human leukemia HL‐60 cells were also examined: Cu2+–4 shows the highest activity with IC50 values of 1.62×10−4 and 1.19×10−5 M, respectively.

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