Evaluation of a New Methylimidazole‐Containing Thiosemicarbazone as a Cu ⁺ /Cu ²⁺ ‐Targeting Ligand in the Context of Alzheimer's Disease

The binding of copper ions to amyloid-β (Aβ) peptide leads to reactive oxygen species (ROS) formation and toxic soluble oligomers, contributing to oxidative stress in Alzheimer's disease (AD). Thus, studying compounds with moderate copper affinity is a promising strategy to prevent its interaction with Aβ and reduce toxicity. Here, we evaluated a new tri-coordinating thiosemicarbazone (HXE) with chelating properties to regulate cuprotoxicity in AD. The ligand was nontoxic against HT-22 hippocampal neuronal cells and bound Cu⁺ and Cu²⁺ at pH 7.4, with affinity constants (log K_cond) of 8.7 and 12.3, respectively, showing high selectivity over Zn²⁺ (log K_app = 5.0). In the presence of Aβ and Cu²⁺, HXE formed stable ternary complexes at physiological pH. Ascorbate consumption and coumarin-3-carboxylic acid fluorescence assays showed that the ligand significantly reduces Cu(Aβ₁₆)-mediated ROS production. It also prevented Cu²⁺-induced modulation of Aβ₄₀ self-assembly and restored the typical fibrillar structure of apo-Aβ₄₀ aggregates. Overall, HXE effectively modulates metal-associated Aβ toxicity and emerges as a promising candidate for AD bioinorganic management.