From Sunscreen to Anticancer Agent: Ruthenium(II) Arene Avobenzone Complexes Display Potent Anticancer Activity

A series of ruthenium(II) arene derivatives (arene = cymene (cym), hexamethylbenzene (hmb)) containing avobenzone (1-(4-tert-butylphenyl)-3-(4-methoxyphenyl)propane-1,3-dione, AVBH) and PTA (1,3,5-triaza-7-phosphaadamantane) or PTA-Me (N-methyl-1,3,5-triaza-7-phosphaadamantane cation) have been synthesized and fully characterized. Three types of complexes have been obtained: i.e., neutral [Ru(arene)(AVB)Cl] (1, arene = cym; 2, arene = hmb), monocationic [Ru(arene)(AVB)(PTA)][SO3CF3] (3, arene = cym; 4, arene = hmb), and dicationic [Ru(arene)(AVB)(PTA-Me)][SO3CF3][BF4] (5, arene = cym; 6, arene = hmb). The solid-state structures of 1 and 2 were determined by single-crystal X-ray diffraction. The cytotoxicity of the complexes has been evaluated in vitro against human ovarian carcinoma cells, A2780 and A2780cisR, as well as against nontumorous Human Embryonic Kidney (HEK293) cells. The ionic complexes with hydrophilic PTA and PTA-Me ligands in 3–6 are considerably more active than the neutral complexes 1 and 2.