Exploring an azo-uracil based nickel(ii) complex for anticancer and phosphatase like activities

An azo-uracil based Ni²⁺ complex (N1) has been synthesized and structurally characterized by spectroscopic techniques, namely FTIR, NMR, ESI-MS and, authenticated by single-crystal X-ray diffraction analyses as a triclinic mononuclear system (CCDC 2003428). The N1 exhibits concentration-dependent cytotoxicity against murine colon carcinoma cell lines (CT26, MC-38) and human colorectal cancer cells (HCT-15) while displaying minimal toxicity toward normal fibroblast NIH-3T3 cells indicating good selectivity. Flow cytometric and fluorescence analyses reveal significant induction of apoptosis in CT26 cells, at sub-micromolar concentration of N1, as evidenced by Annexin V-FITC/PI staining and a dose-dependent increase in early and late apoptotic populations. Mechanistic investigations indicate that N1 induces ROS-mediated, caspase-dependent apoptosis, supported by enhanced intracellular ROS generation and attenuation of cytotoxicity upon ROS scavenging and caspase inhibition. The N1 also interacts efficiently with ct-DNA, exhibiting a binding constant, 2.168 × 10⁵ M^-1. In addition, the N1 demonstrates phosphatase-like catalytic activity, by promoting the hydrolysis of p-nitrophenyl phosphate (p-NPP) under pseudo-first-order conditions with an apparent binding constant (K _app), 1.18 × 10⁵ M^-1. Density functional theoretical (DFT) studies at the TD-SCF/B3LYP/3-21G level support the proposed N1-p-NPP interaction and provide insights into the optimized geometries and associated electronic (HOMO-LUMO) properties. This work bridges catalytic chemistry and cancer biology, positioning the azo-uracil derived Ni(ii) complex as an emerging multifunctional therapeutic candidate.