Cyclometalated platinum(II) complexes bearing natural arylolefin and quinolines ligands: Synthesis, characterizations, and in vitro cytotoxicity

Nine new cyclometalated platinum(II) complexes of the formula [PtCl(arylolefin)(Q)] (2, 3) and [Pt(arylolefin) (N,O)] (4-10) (arylolefinH: eugenoxyacetic acid, isopropyl eugenoxyacetate; Q: quinoline; (N,OH): quinolin-8-ol, 2-methylquinolin-8-ol, 5,7-dichloroquinloin-8-ol and quinoline-2-carboxylic acid] were synthesized and fully characterized by EA, ESI mass spectrometry, IR and NMR spectroscopy and single-crystal X-ray diffraction for 3, 7 and 10. The results show that the arylolefin binds with PtII via the C5 atom of the phenyl ring and the C--C allyl in all the synthesized complexes. Quinoline coordinates with PtII via its N atom in 2, 3, while deprotonated (N, OH) coordinates with PtII via both the N and O atoms in 4-10. The N atom of Q and (N,O) in all complexes are at the cis position with respect to the allyl group of the arylolefin. The XRD confirms the square-planar coordination of PtII and trans position of the arylolefin and quinoline ligands. The results of in vitro cytotoxicity tests against human cancer cell lines KB and Lu of 2, 4-8 indicate that 4 and 5 exhibit the highest activities against Lu and KB cell lines with the IC50 values of 7.1 and 4.1 mu M, respectively, which are approximately 6 and 4 times lower than cisplatin.