Modulation of ruthenium anticancer drugs analogs with tolfenamic acid: Reactivity, biological interactions and growth inhibition of yeast cell.

We synthesized two ruthenium(II) complexes: trans,trans-[Ru(im)2(tfa)2] (1) and trans,trans‑[Ru(in)2(tfa)2] (2) where im = 1H‑imidazole, in = 1H‑indazole and tfa = tolfenamic acid, a potential nonsteroidal anti-inflammatory drug (NSAID). The NSAID was opted as bioactive ligand to understand its synergistic therapeutic effect in structurally analogous Ru(II)-compounds with KP418 (imidazolium trans‑[tetrachloridobis(1H‑imidazole)ruthenate(III)]) and KP1019 (indazolium trans‑[tetrachloridobis(1H‑indazole)ruthenate(III)]). The complexes were studied using various analytical methods and structure was determined by X-ray crystallography. Both the complexes display discrete mononuclear Ru(II) center in {RuN4O2} distorted octahedral geometry. The reactivity of the complexes was tested with potentially important biomolecules involved in metabolism of cancer cells, viz. l‑arginine, dl‑methionine, glutathione and L(+)ascorbate. Such studies intended to provide deeper insights on intracellular speciation and kinetic substitution encountered by Ru-drugs to target alternative cell death pathways. The complexes demonstrate a preferential binding affinity with calf thymus DNA (Kb ~ 104 M-1) and human serum albumin (KHSA = 105 M-1). Both the complexes showed potent inhibition of wild type yeast cell growth in a dose-dependent manner. Yeast cells were used as a powerful model system to study the molecular mechanism of pathobiology which shares a high degree of conservation of both cellular and molecular processes with human cells for assessing toxicity potential of the complexes. Fluorescence imaging studies reveal the localization of both complexes to yeast mitochondria despite its rigid cell wall and induce mitochondrial damage and formation of reactive oxygen species (ROS). The Micrococcal nuclease assay revealed complexes do not alter global nucleosome occupancy and probably target specific regions of the genome.