Interactions of two cytotoxic organoruthenium(II) complexes with G-quadruplex.

Two previously isolated cytotoxic complexes [(η(6)-p-cymene)Ru(κ(2)-CF3COCHCOC5H3O)L](n+) (L=Cl (1); n=0, pta (2) (pta=1,3,5-triaza-7-phosphaadamantane); n=1) were investigated for their selectivity and ability to interact with DNA G-quadruplex adopted by d[G3ATG3ACACAG4ACG3] (3) whose topology exhibits diagonal, edge-type and double-chain reversal loops. Structural changes were followed using high-resolution NMR techniques in the presence of 1 and 2. Results showed weak interaction between the organoruthenium complexes and G-quadruplex. Moreover, no significant changes in thermal stability were confirmed by a UV-melting assay for both 1 and 2. These findings emphasize that anticancer activity of Ru(II) complexes may not be correlated with binding to nucleic acid like G-quadruplex.