Five novel palladium(II) complexes of 8-hydroxyquinoline and amino acids with hydrophobic side chains: synthesis, characterization, cytotoxicity, DNA- and BSA-interaction studies

The side effects and resistance of metal-based anticancer drugs prompted us to synthesis a novel series of five Pd(II) complexes of the type [Pd(8-QO)(AA)]; where 8-QO = anion of 8-hydroxyquinoline and AA = anions of amino acids having nonpolar aliphatic side chain such as glycine (–H), alanine (–CH3), valine (–CH(CH3)2), leucine (–CH2–CH(CH3)2) and isoleucine (–CH(CH3)CH2–CH3). The complexes have been characterized with the help of FT-IR, UV–Vis, one and two-dimensional 1H-NMR, elemental analysis and conductivity measurements. On the basis of these characterization data, a four coordinated square planar geometry for all of these complexes have been proposed. The compounds were screened for their in vitro activities against human cancer cell line, MOLT-4 and their 50% inhibition concentration were ascertained by means of MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay. Since four out of the five newly synthesized compounds were found to be more active than the standard anticancer drug, cisplatin, their detailed interaction with calf thymus DNA (as a target) and bovine serum albumin (BSA) (as a carrier) were also carried out by utilizing absorption spectra, fluorescence spectra and ethidium bromide displacement studies. In these experiments, several binding and thermodynamic parameters were also calculated. These results suggested that hydrogen binding and van der Waals forces play a major role in the interaction between metal complexes with CT-DNA and BSA.

Communicated by Ramaswamy H. Sarma