Evaluation of anticancer capacity, catalase interactions, molecular docking, and antioxidant studies of some diamagnetic (Pd, Pt, and Zn) Schiff base complexes

Abstract

New Schiff base complexes, including diamagnetic metal ions (Pd²⁺/C1, Pt²⁺/C2, Zn²⁺/C3), have been synthesized via appropriate conventional methods using 1-phenyl-1-(pyridin-4-ylimino) propan-2-one oxime (PPYO) as a Schiff base ligand. Theoretical studies confirmed that the C1-C3 have high reactivity and pharmacological potential. The antioxidant activity of the C1-C3 was determined using the DPPH (2,2-diphenyl-1-picrylhydrazyl) method and the following trend was obtained: C1 > C2 > C3 > PPYO. These complexes were able to present good cytotoxic effects on HCT116 colon cancer cells. The trend of anticancer activity is as follows: C2 > C1 > C3. Considering the importance of the antioxidant enzyme catalase in removing reactive oxygen species (ROS), the binding process of C1-C3 with catalase was evaluated. The results showed that C1-C3 can inhibit the catalytic performance of catalase. The C1-C3 quenched the catalase fluorescence emission with a static quenching mechanism. The binding affinity to catalase was almost similar for all three complexes (K_b = 6.37 ± 0.33, 3.23 ± 0.14 and 4.57 ± 0.36 × 10⁵ M⁻¹ for C1, C2 and C3, respectively at 303 K). In C1/C2 interaction with catalase, which was an exothermic and spontaneous process, hydrogen bonds, van der Waals forces, and hydrophobic interactions played a decisive role and were strongly confirmed by molecular docking data. Tracking the structural changes of catalase showed that the enzyme undergoes structural changes in the presence of complexes.