In vitro cytotoxicity studies of palladacyclic complexes containing the symmetric diphosphine bridging ligand. Studies of their interactions with DNA and BSA

• Two new palladacyclic–dppe complexes (1 and 2) were synthesized.
• 1 and 2 exhibit cytotoxicity against Hela, HT-29, K562 and MCF-7 tumor cell lines.
• The DNA-binding abilities are consistent with cytotoxicity in the order 2 > 1.
• Complex 2 exhibits higher BSA binding ability than that of complex 1.

The reactions between [Pd2{(C,N)–C6H4CH2NH(Et)}2(μ-X)2] (X = Cl or Br) and 1,2-bis(diphenylphosphino)ethane (dppe) in the 1:1 molar ratio resulted in the dppe-bridged Pd(II) complexes, [Pd2{(C,N)–C6H4CH2NH(Et)}2(μ-dppe)(Cl)2] (1) and [Pd2{(C,N)–C6H4CH2NH(Et)}2(μ-dppe)(Br)2] (2), respectively, which were characterized by elemental analyses, infrared (IR), 1H- and 31P{1H} NMR spectroscopy. The molecular structure of 1 was determined by single-crystal X-ray diffraction. In vitro cytotoxicity of 1, 2, dppe, PhCH2NH(Et) and cisplatin were carried out against four human tumor cell lines. The interactions of complexes towards DNA and protein are investigated. The results suggested that both complexes could interact with FS-DNA through the intercalation mode. Moreover, the reactivity towards BSA revealed that the microenvironment and the secondary structure of BSA were changed in the presence of Pd(II) complexes.

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