Synthesis, structure and in vitro cytotoxicity of platinum(II) complexes containing eugenol and a quinolin-8-ol-derived chelator

The synthesis of potassium (η2-4-allyl-2-methoxyphenol)trichloridoplatinate(II), K[PtCl3(C10H12O2)], (1), starting from Zeise's salt and Ocimum sanctum L. oil has been optimized. Starting from (1), three new platinum(II) complexes, namely (η2-4-allyl-2-methoxyphenol)chlorido(2-methylquinolin-8-olato-κ2N,O)platinum(II), (2), (η2-4-allyl-2-methoxyphenol)chlorido(5-nitroquinolin-8-olato-κ2N,O)platinum(II), (3), and (η2-4-allyl-2-methoxyphenol)chlorido(5,7-dichloroquinolin-8-olato-κ2N,O)platinum(II), [Pt(C9H4Cl2NO)Cl(C10H12O2)], (4), containing eugenol and a quinolin-8-ol derivative (R-OQ), have been synthesized and characterized by elemental analyses, MS, IR, 1H NMR and NOESY spectra. For (1) and (4), single-crystal X-ray diffraction studies were also carried out. Complexes (2)-(4) show good inhibiting abilities on three human cancer cell lines, i.e. KB, Hep-G2 and LU, with IC50 values of 1.42-17.8 µM. Complex (3) gives an impressively high activity against KB, Hep-G2, LU and MCF-7, with IC50 values of 1.42-4.91 µM, which are much lower than those of cisplatin and some other platinum(II) complexes.