Diclofenac-Copper(II) complex and Kigelia pinnata-derived Ag/Mn nanocomposites: Synthesis, characterization, molecular docking and comparative antibacterial activity

The development of novel antimicrobial agents remains urgent in the face of drug-resistant infections. Here, we report a comparative study of a synthetic diclofenac-based copper(II) complex and two green-synthesized nanocomposites derived from Kigelia pinnata extracts. The diclofenac–Cu(II) complex, tetrakis{µ-2-[2-(2,6-dichloroanilino)phenyl]acetato-κ²O:O’}bis(methanol-κO)copper(II), was synthesized, characterized by LC–MS and UV–Vis spectroscopy, and evaluated alongside an imidazole-ligated intermediate. In silico docking revealed strong predicted interactions of the diclofenac complex with bacterial nutrient-sensing proteins, notably E. coli UhpC and PfkB kinases, and Staphylococcus ECF transporters. Parallel LC–QTOF–MS profiling of Kigelia fruit and bark extracts identified abundant naphthoquinones and flavonoids, which facilitated the green synthesis of silver (AgNC) and manganese (MnNC) nanocomposites. SEM–EDX confirmed nanoscale morphology, with AgNCs composed of elemental silver and MnNCs containing Mn–oxide phases. Antimicrobial activity was compared against E. coli and Staphylococcus vitulinus. AgNCs demonstrated the highest potency (MIC ≤15.63 µg/mL for S. vitulinus; 62.5 µg/mL for E. coli), outperforming MnNCs (31.25–62.5 µg/mL) and the diclofenac–Cu(II) complex (256 µg/mL against Gram-positive strains only). The findings highlight the superior antibacterial performance of silver nanocomposites while confirming that copper complexes remain selectively active against Gram-positive pathogens.