Vitamin-B6 Schiff base dioxovanadium(V) complex for targeted visible light-induced anticancer activity

Abstract

A dioxovanadium(V) complex of vitamin-B6 Schiff base [VO₂L] (1) (where H₂L·HCl is 3-hydroxy-5-(hydroxymethyl)-4-(((2-hydroxyphenyl)imino)methyl)-2-methylpyridin-1-ium chloride) has been prepared and structurally characterized. Its photo-induced cytotoxicity and mechanism of cell death has been studied. Single crystal X-ray structure shows five-coordinate square-pyramidal geometry of the complex having the dianionic O,N,O-donor tridentate vitamin-B6 Schiff base and two cis-oriented oxo ligands bound to V(V). DFT study shows the HOMO located on the amino-phenolic moiety, while the LUMO is on the protonated aromatic unit, i.e., the pyridiniumphenolate moiety. Vitamin-B6 transporting membrane carrier (VTC) pathway seems to be responsible for the higher cellular uptake and activity of the complex into the cervical HeLa and breast cancer MCF-7 cells in preference to the normal embryonic fibroblast 3T3 cells. The complex exhibits reactive oxygen species (ROS) mediated apoptotic photocytotoxicity in visible light of 400–700 nm in the cancer cells (IC₅₀: ~16 μM), while being essentially non-toxic in the dark. Alkaline Comet assay shows damage of the nuclear DNA.