Synthesis, characterization, HSA/DNA binding, cytotoxicity study, and antimicrobial activity of new palladium(II) complexes with some esters of (S,S)-propylenediamine-N,N'-di-2-(3-methyl)butanoic acid

Abstract

In this paper, we presented synthesis, characterization, HSA/DNA binding evaluation, in vitro cytotoxic activity and in vitro antimicrobial activity of three new ligands of general formula. R2-S,S-pddmb (L1-L3) and their corresponding palladium(II) complexes of general formula [PdCl2(R2-S,S-pddmb)] (R = n-propyl, n-butyl, n-pentyl; S,S-pddmb = (S,S)-propylenediamine-N,N'-di-2-(3-methyl)-butanoate). Ligands and complexes were characterized by elemental microanalysis, infrared, 1H and 13C NMR spectroscopy. The interactions of new palladium(II) complexes with human serum albumin (HSA) and calf thymus DNA (CT-DNA) were investigated using UV–Vis absorption and fluorescence spectroscopy. The high values of the binding constant, Kb, and the Stern-Volmer quenching constant, KSV, are the result of good binding of all complexes to HSA and CT-DNA. In vitro cytotoxic activity of these ligands and complexes was evaluated against four tumor cell lines, 4 T1, CT26, MDA-MD-468, HCT116 and mesenchymal stem cells (mMSC). C3 complex showed high cytotoxic activity against MDA-MD-468 cell line. Flow cytometry analysis showed that L3 ligand and the corresponding complex (C3) stimulated apoptosis of tumor cells via inhibition of expression of antiapoptotic Bcl-2 molecule. L3 ligand and C3 complex slowed down cell proliferation and arrested tumor cell in the G0/G1 phase by decreasing Cyclin-D expression and by increasing expression of P21. In vitro antimicrobial activity of ligands and complexes was also investigated. The testing was performed by microdilution method and minimum inhibitory concentration (MIC) and minimum microbicidal concentration (MMC) were determined. The testing was conducted against 12 microorganisms. The tested ligands and palladium(II) complexes showed selective and moderate activity.