A Highly Luminescent Tetrahydrocurcumin Ir III Complex with Remarkable Photoactivated Anticancer Activity

• Published in: Chemistry : a European journal Vol. 25; no. 33; pp. 7948 - 7952
• Main Authors: Colombo, Alessia, Fontani, Mattia, Dragonetti, Claudia, Roberto, Dominique, Williams, J A Gareth, Scotto di Perrotolo, Rossella, Casagrande, Francesca, Barozzi, Sara, Polo, Simona
• Format: Journal Article
• Language: English
• Published: Germany 12-06-2019
• Subjects: iridium; tetrahydrocurcumin; natural products; photodynamic therapy; imaging agents; anticancer agents; curcumin
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.201901527

Curcumin has chemopreventative properties against a variety of tumours, but has poor bioavailability. Here, two new bis-cyclometallated iridium(III) complexes have been prepared, featuring the natural product curcumin (CUR) or its reduced form, tetrahydrocurcumin (THC), as bidentate, anionic O O-binding ligands. The iridium THC complex is highly luminescent in deoxygenated solution and efficiently generates singlet oxygen under aerated conditions, whereas in the CUR analogue, other non-radiative decay pathways are competitive. The complexes are rapidly taken up by a variety of human tumour cell lines from solutions of micromolar concentration. They show negligible cytotoxicity in the absence of irradiation. When briefly irradiated with visible light, Ir-THC becomes highly phototoxic, inducing rapid apoptosis within 2 h. The results show the high potential of such complexes as sensitizers in photodynamic therapy (PDT).