Transfer Hydrogenation and Antiproliferative Activity of Tethered Half-Sandwich Organoruthenium Catalysts.

We report the synthesis and characterization of four neutral organometallic tethered complexes, [Ru(η-Ph(CH)-ethylenediamine--R)Cl], where R = methanesulfonyl (Ms, ), toluenesulfonyl (Ts, ), 4-trifluoromethylbenzenesulfonyl (Tf, ), and 4-nitrobenzenesulfonyl (Nb, ), including their X-ray crystal structures. These complexes exhibit moderate antiproliferative activity toward human ovarian, lung, hepatocellular, and breast cancer cell lines. Complex in particular exhibits a low cross-resistance with cisplatin. The complexes show potent catalytic activity in the transfer hydrogenation of NAD to NADH with formate as hydride donor in aqueous solution (310 K, pH 7). Substituents on the chelated ligand decreased the turnover frequency in the order Nb > Tf > Ts > Ms. An enhancement of antiproliferative activity (up to 22%) was observed on coadministration with nontoxic concentrations of sodium formate (0.5-2 mM). Complex binds to nucleobase guanine (9-EtG), but DNA appears not to be the target, as little binding to calf thymus DNA or bacterial plasmid DNA was observed. In addition, complex reacts rapidly with glutathione (GSH), which might hamper transfer hydrogenation reactions in cells. Complex induced a dose-dependent G cell cycle arrest after 24 h exposure in A2780 human ovarian cancer cells while promoting an increase in reactive oxygen species (ROS), which is likely to contribute to its antiproliferative activity.