Metal-binding effects of sirtuin inhibitor sirtinol.

Sirtinol, a Schiff base derived from 2-hydroxy-1-naphthaldehyde, is an inhibitor of sirtuin proteins, a family of deacetylases active in gene regulation and relevant to the study of cancer growth. The formation of copper(II) and zinc(II) complexes of sirtinol is investigated by spectroscopic and structural methods. The molecular structure of this protein inhibitor allows for coordination of first-row transition metals in both tridentate and bidentate fashion. In addition, assays in cultured breast cancer cells reveal that CuII(sirtinol-H)2 and previously reported FeIII(sirtinol-H)(NO3)2 present enhanced cytotoxicity when compared to the free ligand, and that the ferric complex causes an increase in intracellular oxidative stress. Transition metal coordination in the biological milieu could therefore contribute additional effects to the biological profile of sirtinol.