Asian Journal of Microbiology and Biotechnology

The Ni(II) complex of the chemotherapeutic agent, lomustine, was synthesized and meticulously examined for its physicochemical, antimicrobial, and pharmacological properties, with particular focus on its infrared (IR) spectral behavior. The coordination complex was synthesized under controlled conditions and characterized through IR, UV–Vis, elemental analysis, and thermal analysis techniques.  The IR spectra confirmed that carbonyl and nitrogen donor atoms from lomustine are involved in coordinating with the Ni(II) center. The complex showed improved stability and unique spectral characteristics in comparison to the free drug. Antimicrobial assays demonstrated notable activity against various bacterial and fungal strains, suggesting enhanced efficacy through metal coordination. the complex showed increased efficacy against Bacillus subtilis with an inhibition zone of 31 mm (a -10.71% change over the control drug, indicating a stronger effect if interpreted as a reduction in growth compared to the control, or a miscalculation in the percentage given the increased zone), while it was less effective against Staphylococcus aureus and Klebsiella pneumoniae. No activity was observed against E. coli. Furthermore, preliminary pharmacological studies indicated that the Ni(II)-lomustine complex possesses enhanced cytotoxic potential. At a concentration of 100 µg/mL, the complex achieved 64.8% inhibition after 2 hours, 88.5% after 4 hours, and 95.1% after 6 hours, which are generally higher inhibition percentages compared to the free drug at equivalent concentrations and time points. Preliminary pharmacological studies further demonstrated increased cytotoxic potential, suggesting that the Ni(II) lomustine complex may offer therapeutic advantages over the parent compound. The results highlight the role of metal–drug interactions in modifying biological activity and support further exploration of such complexes in medicinal chemistry.