Biological evaluation of organometallic palladium(II) complexes containing 4-hydroxybenzoic acid (3-ethoxy-2-hydroxybenzylidene)hydrazide: Synthesis, structure, DNA/protein binding, antioxidant activity and cytotoxicity

New palladium(II) complexes, [Pd(PPh3)L] (2) and [Pd(AsPh3)L] (3), were synthesized using 4-hydroxybenzoic acid (3-ethoxy-2-hydroxybenzylidene)hydrazide (1) ligand (H2L), and characterized using various physicochemical techniques. The molecular structures of 2 and 3 were determined using single-crystal X-ray diffraction, which reveals a square planar geometry around the palladium(II) metal ion. In vitro DNA binding studies were conducted using UV-visible absorption spectroscopy, emission spectroscopy, cyclic voltammetry and viscosity measurements, which suggest that the metal complexes act as efficient DNA binders. The interaction of ligand H2L and complexes 2 and 3 with bovine serum albumin (BSA) was investigated using UV-visible and fluorescence spectroscopies. Absorption and emission spectral studies indicate that complexes 2 and 3 interact with BSA protein more strongly than the parent ligand. The free radical scavenging potential of all the synthesised compounds (1-3) was also investigated under in vitro conditions. In addition, the in vitro cytotoxicity of the complexes to tumour cells lines (HeLa and MCF-7) was examined using the MTT assay method.