Polytopic carriers for platinum ions: from digalloyl depside to tannic acid

A novel dinuclear platinum(ii) complex, namely [Pt2m-GG(Me2SO-S)4] (8, GG = deprotonated methyl digallate), was easily synthesized under solvent-free conditions by grinding a solid m/p digalloyl depside with the Pt precursor [PtCO3(Me2SO-S)2]. Similarly, platinum nuclei were introduced into the galloyl chains of tannic acid (TA). In particular, three complexes A, B and C were prepared by reacting TA as a polytopic ligand with an increasing amount of [PtCO3(Me2SO-S)2]. The antiproliferative activity of complexes 8, A, B and C together with the corresponding ligands GG and TA was tested in vitro and compared with that of cisplatin on two human tumor cell lines, A2780 (ovarian cisplatin-sensitive) and A2780cis (ovarian cisplatin-resistant), and one non-tumoral cell line, HaCat. The experiments focusing on their pro-apoptotic activity indicated that the antiproliferative activity of the most active Pt(II) complexes is associated with the induction of apoptosis.