No specific SAR (structure-activity relationships) could be identified. Both the attached unit and the connector play a significant role in the biological activity. The most interesting compounds that deserve to be considered for further studies are ester 14 (conjugated to 9-(2-oxyethyl)adenine) and click product 36 (bearing a 2-(4-(hydroxymethyl)-1H-1,2,3-triazol-1-yl)methyl substituent). Non-infected HFF monolayers treated only with 0.1% DMSO exhibited 100% viability and 100% proliferation was attributed to T. gondii β-gal tachyzoites treated only with 0.1% DMSO. For each assay, standard deviations were calculated from triplicates and are displayed on the graph. Data for compounds 2-4 and 8 were previously reported . The mechanism of action of the trithiolato diruthenium compounds has not been yet elucidated. These compounds generally exhibit reduced water solubility and contrary to other Ru(II)-arene complexes presenting labile chlorine or carboxylate ligands, they do not hydrolyze and are stable in the presence of most biomolecules such as amino acids and DNA . Only the oxidation of cysteine (Cys) and glutathione (GSH) to form cystine and GSSG, respectively, was observed in the presence of some compounds, but no correlation between the in vitro cytotoxicity and the catalytic activity on the oxidation reaction of glutathione was observed .