Functionalized nitro-piperonal thiosemicarbazone based ruthenium(ii)-arene complexes for DNA interaction, anticancer and flow cytometry studies

Functionalized thiosemicarbazones derived from 6-nitro piperonal and their corresponding Ru(ii)-(η⁶-benzene) (RuBNPT, RuBNMT, RuBNCT and RuBNMeT)/(η⁶-p-cymene) (RuPNPT, RuPNMT, RuPNCT and RuPNMeT) complexes were synthesized and explored for their biological efficacy and anticancer potential. The impact on the complexes’ electronic characteristics, coordination affinity, and bioactivity of the piperonal substitution at the N(4)-position with morpholine (6NMT), pyrrolidine (6NPT), cyclohexyl (6NCT), and N-methyl (6NMeT) groups were investigated. Comprehensive characterization using UV-vis, FT-IR, NMR (¹H and ¹³C), HRMS, and XRD (6NPT and RuPNMT) confirmed the structural integrity of the synthesized compounds. Density functional theory (DFT) calculations revealed insights into electronic and physicochemical properties, while molecular docking studies demonstrated effective binding with the EGFR, suggesting their potential as anticancer agents. DNA and BSA binding studies indicated intercalative and hydrophobic interactions, with RuPNMT exhibiting moderate binding affinity. Cytotoxicity assays, including MTT assay results, indicated the strong activity of the RuPNMT and RuPNPT compounds (RuPNMT and RuPNPT exhibited IC₅₀ values of 10.5 μM and 27.2 μM, respectively, in MDA-MB-231 cells, and 24.6 μM and 58.1 μM in MCF-7 cells). Additionally, apoptosis studies were conducted on these compounds using AO-EB staining and flow cytometry. The presence of heteroatoms and planarity of the N(4)-substituent enhanced the bioactivity of the ligands, while coordination with Ru(ii)-arene precursors further amplified their effectiveness. This study underscores the effectiveness of these complexes as promising agents for targeted cancer treatment.