New Organoruthenium(II) Complexes Containing Andrographolide-Appended Hydrazide Derivatives: Synthesis, Spectral Characterization, Anticancer Evaluation

Abstract

A new set of andrographolide-appended hydrazide derivatives (AFC, AGC, and ATC) were prepared from the reaction of andrographolide with furan-2-carboxylic acid hydrazide (AFC), pyridine-3-carboxylic acid hydrazide (AGC), and thiophene 2-carboxylic acid hydrazide (ATC), and their corresponding ruthenium(II) complexes (Ru-AFC, Ru-AGC, and Ru-ATC) were synthesized by the direct reaction of [RuCl₂(η⁶-p-cymene)]₂ with ligands in dichloromethane under stirring condition. The compounds were analyzed by elemental analysis, IR, UV-Vis, ¹H NMR, and ESI-MS spectrometric techniques, and the obtained spectral data revealed that the ligands coordinated to Ru(II) ion through their enone oxygen and amine nitrogen. Antioxidant activities of the ligands and complexes were calculated against DPPH^•, ABTS^•+, O²⁻, and NO^• free radicals and their results were compared with standard antioxidants. The cytotoxic activity of the synthesized ligands and complexes toward A549 and HeLa cell lines was evaluated using MTT method (MTT = 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide). Among the compounds, the complex Ru-AGC showed better cytotoxic effect against A549 and HeLa cancer cells with IC₅₀ values of 4.75 ± 0.17 and 6.32 ± 0.26 μM, respectively. Further, the nontoxic nature of the compounds was confirmed by using human umbilical vein endothelial (HUVEC) cells. The apoptosis was inspected with AO/EB and DAPI staining methods; further, the percentages of the apoptotic and necrotic cells were determined by flow cytometry. Overall, the biological activities of our ruthenium(II)-arene complexes were found to be more potent than their parent ligands due to chelation, and among the complexes, Ru-AGC showed better activity due to the presence of pyridine ring in the N-terminal position of the ligand. The obtained results highlighted the strong possibility to develop highly active ruthenium complexes as anticancer agents.