Physicochemical properties and anticancer activity of copper complexes [Cu(L-Leu-L-Phe)] and [Cu(L-Phe-L-Leu)]

To investigate how the sequence of dipeptide isomers (L-Phe-L-Leu and L-Leu-L-Phe) influences the physicochemical properties and anticancer activity of their copper complexes, two complexes [Cu(L-Leu-L-Phe)] (1) and [Cu(L-Phe-L-Leu)] (2) were prepared using a method modified from literatures. The complexes were characterized via single-crystal X-ray diffraction, thermogravimetric analysis, and IR spectroscopy. Assessments included optical rotation, UV–Vis spectra, and antiproliferative activity against the human esophageal carcinoma cell line Ec9706. Both complexes exhibit similar UV–Vis spectra and thermal stability but differ in specific optical rotation (1: 862.3; 2: 476.3). In anticancer assays, complex 1 (IC₅₀ = = 45.7, 95 % CI 37.2–55.9 μM) showed stronger activity against Ec9706 cells than complex 2 (IC₅₀ = 71.4, 95 % CI 66.8–76.8 μM), with both showing an antiproliferative effect. These findings provide a basis for developing peptide-based anticancer agents.