Synthesis, characterization, DNA, BSA, antimicrobial, antioxidant and molecular docking studies of gadolinium(III) based complexes

Abstract

The present study reports the synthesis of two new gadolinium-metal-based complexes with mixed ligands, [Gd(L1)₂(py)(H₂O)₃] (C1) and [Gd (L2)₂(phen)(H₂O)₂] (C2), where L1 represents 3-(4 cyanophenyl) acrylate and L2 as 3-(4 fluorophenyl) acrylate. The complexes were characterized by various analytical techniques including FT-IR, PXRD, TGA, DSC, SEM and EDX to determine structural elucidation, binding mode, crystallinity, thermal stability, morphology and elemental composition, respectively. The synthesized complexes were tested for DNA (salmon sperm) and BSA interaction studies to infer their antitumor potential. The binding constants obtained for C1 and C2 with SS DNA were 3.03 × 10⁴ and 3.2 × 10⁴ while with BSA observed as 1.59 × 10⁵ and 1.22 × 10⁵, respectively. In vitro antimicrobial potential of both complexes was determined against various bacterial and fungal strains. Experimental results showed complex C2 is more active than C1 against all selected bacterial strains and showed higher antibacterial potential against E. coli with a zone of inhibition (ZOI) of 35 mm. The antibacterial potential of C2 was further investigated by calculating the MIC (IC50) value. MIC of complex C2 was assessed using visual inspection (turbidity) and spectrophotometric assay at 600 nm. The findings of the spectrophotometric approach have greater sensitivity than the standard disc diffusion assays. The molecular docking studies were conducted to validate further and compare the findings of experimental results which exhibited that complex C2 has an excellent binding capacity with the target protein (5CDQ) with free binding energy −12.23 kcal/mol. Antioxidant potentials of the complexes were assessed using phosphomolybdenum assay, which demonstrated that complex C2 exhibits higher antioxidant activity than complex C1.