Mechanistic insights into the anticancer potential of ruthenium(II) paracymene complexes of phenolic acids

Organometallics, specifically ruthenium (Ru)-based complexes, have emerged as promising anticancer agents, offering controlled reactivity, electronic versatility, and tunable lipophilicity. The present work focuses on elucidating detailed anticancer cellular mechanisms of Ru(II)-gallate and Ru(II)-vanillate against MCF-7 breast and HepG2 liver cancer cells. Cell death pattern was assessed by flow cytometry, reactive oxygen species (ROS) level and mitochondrial membrane potential were measured by fluorescence assay, and the expression of key apoptosis-related proteins and genes were quantified by Western blot and quantitative reverse transcription polymerase chain reaction, respectively. Acute toxicity study was conducted in female Swiss albino mice. Mechanistic assays confirmed that both complexes substantially disrupted intracellular redox homeostasis, as evidenced by characteristic alterations in reduced glutathione/oxidized glutathione ratio indicative of reductive stress, leading to mitochondrial membrane depolarization, induced apoptotic cell death, suppressed anti-apoptotic protein B-cell lymphoma-2 (Bcl-2), pro-caspase-3 levels (in HepG2 cells only), promoted mitochondrial cytochrome c release, elicited a concomitant rise in caspase-9, and upregulated Bcl-2-associated X-protein. The protein expression profile was further supplemented by analysis of important genes associated with apoptosis, such as BAX, BCL2, CASP3, and CASP9, performed using quantitative reverse transcription polymerase chain reaction. Acute oral toxicity study at a limit dose of 2000 mg/kg did not reveal adverse hematological, biochemical, or histopathological alterations in mice, indicating a non-toxic outcome under the tested conditions. This study revealed that Ru(II)-gallate and Ru(II)-vanillate induce mitochondria-mediated apoptosis driven by reductive stress, and exhibited strong in vivo tolerability, underscoring their potential as attractive contenders for cancer treatment pending further evaluation.