Triazole-Based Half-Sandwich Ruthenium(II) Compounds: From In Vitro Antiproliferative Potential to In Vivo Toxicity...

A new series of half-sandwich ruthenium(II) compounds [(η⁶-arene)Ru(L)Cl][CF₃SO₃] bearing 1,2,3-triazole ligands (arene = p-cymene, L = L1 (1); arene = p-cymene, L = L2 (2); arene = benzene, L = L1 (3); arene = benzene, L2 (4); L1 = 2-[1-(p-tolyl)-1H-1,2,3-triazol-4-yl]pyridine and L2 = 1,1'-di-p-tolyl-1H,1'H-4,4'-bi(1,2,3-triazole) have been synthesized and fully characterized by ¹H and ¹³C NMR and IR spectroscopy, mass spectrometry, and elemental analysis. The molecular structures of 1, 2, and 4 have been determined by single-crystal X-ray diffraction. The cytotoxic activity of 1-4 was evaluated using the MTS assay against human tumor cells, namely ovarian carcinoma (A2780), colorectal carcinoma (HCT116), and colorectal carcinoma resistant to doxorubicin (HCT116dox), and against normal primary fibroblasts. Whereas compounds 2 and 4 showed no cytotoxic activity toward tumor cell lines, compounds 1 and 3 were active in A2780, while showing no antiproliferative effect in human normal dermal fibroblasts at the IC₅₀ concentrations of the A2780 cell line. Exposure of ovarian carcinoma cells to IC₅₀ concentrations of compound 1 or 3 led to an accumulation of reactive oxygen species and an increase of apoptotic and autophagic cells. While compound 3 displayed low levels of angiogenesis induction, compound 1 showed an ability to induce cell cycle delay and to interfere with cell migration. When the in vivo toxicity studies using zebrafish and chicken embryos are considered, compounds 1 and 3, which were not lethal, are promising candidates as anticancer agents against ovarian cancer due to their good cytotoxic activity in tumor cells and their low toxicity both in vitro and in vivo.