Synthesis, spectroscopic, and photophysical studies of Mn(II), Co(II), and Zn(II) complexes with 3-hydroxyflavone: Insights into anticancer activity against prostate cancer cells.

This study reports the synthesis, spectroscopic and photophysical characterization, and anticancer evaluation of Mn(II), Co(II), and Zn(II) complexes with 3-hydroxyflavone. The complexes were obtained in a 1:2 metal-to-ligand molar ratio, yielding solid mononuclear species with the general formula ML2·nH2O, where M = Mn(II), Co(II), or Zn(II), and L⁻ = 3-hydroxyflavonate. The compounds were characterized by elemental analysis, thermogravimetric analysis (TG/DTG-DSC), differential scanning calorimetry, UV-Vis, FT-IR, NMR, 109AgNP LDI MS (Fiber Laser-Generated Silver-109 Nanoparticles for Laser Desorption/Ionization Mass Spectrometry), and fluorescence spectroscopy. Spectroscopic studies indicated coordination through 3-hydroxy and carbonyl groups, leading to structural and electronic modifications of the ligand. Fluorescence properties were strongly influenced by metal coordination, with Zn-3-hydroxyflavone showing the most pronounced emission changes due to altered excited-state intramolecular proton transfer. The cytotoxic activity of the complexes was evaluated against prostate cancer (DU-145), normal prostate (RWPE-2), and normal fibroblast (BJ) cell lines. Zn-3-hydroxyflavone exhibited the highest anticancer activity, with a half-maximal inhibitory concentration (IC50) of 4.08 μM. All complexes displayed selective cytotoxicity, as evidenced by the high viability of normal cell lines even at concentrations exceeding their IC50 values. Recovery assays revealed either a permanent cytotoxic effect or partial regeneration of DU-145 cells following exposure to the complexes. Real-time detection of phosphatidylserine externalization, a key marker of apoptosis, indicated that induction of apoptosis is the most probable mechanism of action for the Mn(II) and Zn(II) complexes against prostate cancer cells.