New salen-type manganese(III) Schiff base complexes derived from <i>meso</i>-1,2-diphenyl-1,2-ethylenediamine: <i>In vitro</i> anticancer activity, mechanism of action, and molecular docking studies

<div><p>Four new manganese(III) Schiff base complexes (<b>1–4</b>) were synthesized and characterized. The complexes have general formula [MnClL^x] in which L represents a Schiff base ligand derived from condensation of <i>meso</i>-1,2-diphenyl-1,2-ethylenediamine with salicylaldehyde or its 3-OMe-, 5-Br-, or 5-OMe-derivatives (<i>x</i> = 1–4, respectively). The crystal structure of [MnClL¹] (<b>1</b>) was characterized by X-ray crystallography. The <i>in vitro</i> anticancer activity of these complexes was evaluated by MTT and apoptosis assays against human breast (MCF-7) and liver (Hep G2) cancer cells. The complexes exhibited considerable antiproliferative activity against both cell lines (IC₅₀ = 10.8–21.02 μM) comparable to cis-platin, except <b>4</b> (MCF-7). The highest activity was found for <b>1</b> with IC₅₀ values of 13.62 μM (MCF-7) and 10.8 μM (Hep G2). Flow cytometry experiments showed that <b>1</b> induced apoptosis on MCF-7 tumor cell line. Docking simulations using AUTODOCK were also carried out. The results showed that all complexes fitted into the minor groove region of DNA.</p></div