Design, Synthesis, Structural Characterization and Bioactivity of Novel Halolactones Derived from Vanillin: Antiproliferative and Hemolytic Potential

A series of novel γ-halo-δ-lactones and δ-halo-γ-lactones bearing a phenolic ring at the β-position was synthesized from the naturally occurring aromatic aldehyde vanillin. The seven-step synthetic route commenced with benzyl protection of the hydroxy group of the starting material, followed by the synthesis of a γ,δ-unsaturated carbox-ylic acid, subsequent halolactonization (iodo-, bromo-, and chlorolactonization), and concluded with selective benzyl deprotection. The structures of all synthesized com-pounds were confirmed by comprehensive spectroscopic analyses, including NMR and HRMS. The resulting halolactones were evaluated for antiproliferative activity against two canine (CLBL-1, CLB70) and two human (T-24, CaCo-2) cancer cell lines, with non-cancerous mouse embryonic fibroblasts (NIH/3T3) serving as controls. Hemolytic assays were performed to assess toxicity toward human red blood cells (RBCs). All compounds demonstrated selective inhibition of cancer cell proliferation, exhibiting no inhibitory effects on normal fibroblasts and no hemolytic toxicity. Among the tested lactones, the trans δ-iodo-γ-lactone was the most potent, particularly against CLBL-1 and T-24 cells. These findings underscore the potential of vanillin-derived halolactones as selective anticancer agents with an advantageous safety profile, owing to their lack of toxicity toward non-malignant cells.