Organotin carboxylates with bulky substituents. Synthesis, structure, cytotoxicity and antioxidant activity

A series of organotin carboxylates were synthesized and characterized by NMR (¹H, ¹³C, ¹¹⁹Sn) and IR spectroscopy, ESI mass-spectrometry and elemental analysis. The structure of two compounds was resolved directly using X-ray diffraction analysis and unusual heptacoordinated Sn coordination polyhedron was discovered for them. Antioxidant activity of the synthesized compounds was estimated using DPPH, NBT and CUPRAC-tests, lipid peroxidation and lipoxygenase inhibition capacity as well. It was shown that the presence of the hydroxyl group in the aromatic ring of the ligand drastically increases antioxidant potency of the complexes, while not noticeably affecting the antiproliferative properties, which were measured with the standard MTT-test. Moreover, it was shown that derivatives of dibutyl- and di-tert-butyltin exhibit the highest cytotoxicity. Three complexes were put forward as lead compounds and additional apoptosis induction studies were carried out. Noticeable caspase activation was shown for the complexes 4 and 7 thus marking their mode of action. The results obtained show that the complexes herein described are promising antiproliferative agents.