Synthesis and characterization for new Mn(II) complexes; conductometry, DFT, antioxidant activity via enhancing superoxide dismutase enzymes that confirmed by in-silico and in-vitro ways

Two novel Mn(II) complexes were prepared from new simple ligands. The two complexes were isolated in the form of 1:1 molar ratio via coordination mode of neutral bidentate. This formula was suggested based on CHN, mass spectra and EDX analysis. HL1 ligand coordinated by C=O and C=N groups, while H2L2 ligand coordinated by C=O-13 and C-S groups. The tetrahedral geometry was the structural form suggested for the two Mn(II) complexes according to electronic transitions assign for (6)A(1)g ->(4)Eg(4D) and (6)A(1)g ->(4)T(1)g(4P). Conductometric titrations were carried out to estimate essential constants for the complex in solution sate. Using density-functional theory (DFT) via Gaussian 09 program, we optimized the structural forms of the ligands and their complexes. Valence double-zeta polarized basis set (6-31G*) and efficient core potential basis set (SDD) level were the two sets adjusted for optimizing the ligands and their Mn(II) complexes, respectively. The calculated parameters as well as the electrostatic potential maps (MEP) support the mode of bonding inside the complexes which agreed with the practical data. Also, functional activity relationships were obtained after calculating important physical parameters which suggest the superiority of two Mn(II) complexes in catalytic behavior with superoxide dismutase (SOD) enzyme. Interestingly, the antioxidant activity of the complexes was examined computationally (in-silico) and practically (in-vitro), to evaluate mimic MnSOD enzyme feature. Pharmacophore query was done according to ligand-based, to get a brief view about the ability of complexes to enhance SOD-enzyme function. The two complexes could being able to resident slightly the active core in 3cei and 2pgc proteins, which leads to improve antioxidant function of SOD-enzyme, to be mimic MnSOD-enzyme. This suggestion was further supported by MOE-docking approach which offered all interaction details. Moreover, in-vitro assay results exhibited antioxidant feature of the two complexes which reach up to 87% and surely considered promising. Finally, from in-silico and in-vitro assessments, we could introduce such two Mn(II) complexes as a mimic MnSOD enzyme in its antioxidant function. (C) 2021 Elsevier B.V. All rights reserved.