New organotropic compounds. Synthesis, characterization and reactivity of Pt(II) and Au(III) complexes with bile acids: DNA interactions and 'in vitro' anticancer activity.

Based on the ability of bile acids to vectorialize the cytostatic activity of other agents, we have designed and synthesized a new series of platinum and gold complexes. These compounds were studied and characterized by elemental analysis, FT-IR, FAB(+)/MS, 1H, 13C and 195Pt NMR, UV-Vis spectroscopy and conductivity measurements in solution, among other techniques. Kinetic studies carried out in aqueous solution and in the presence of different NaCl concentrations: 4 mM (similar to cytoplasmic concentration), 150 mM (similar to plasmatic concentration). The effects on the electrophoretic mobility of the pUC18 plasmid, the DNA denaturation temperature, and ethidium bromide (EtBr) binding to DNA were studied. The complexes are able to inter-react with DNA to inhibit DNA synthesis and hence, to reduce cell proliferation. The complexes were evaluated for in vitro cytostatic activity against human colon adenocarcinoma, mouse hepatoma, human hepatoma, mouse leukemia, etc. The antitumor effect of some of the compounds prepared was similar to that of cisplatin. However, other compounds had lower cytostatic activity. This different behavior can be accounted for by the structure/activity relationship (SAR), although other factors, such as uptake and the different kinetic behavior in solution, may be responsible for these differences.