Bacillus cereus is a widespread Gram-positive bacterium that can cause severe foodborne illnesses, opportunistic infections, and even life-threatening conditions such as endophthalmitis and bacteremia. Its pathogenic potential, combined with the ability to produce toxins and form resistant spores, makes it a serious public health concern. In recent years, the problem has been exacerbated by the increasing occurrence of antibiotic resistance in B. cereus, which reduces the effectiveness of conventional treatments. Therefore, the discovery and development of new drug candidates with strong antibacterial activity against B. cereus is of great importance. Since thiosemicarbazones and their metal coordination complexes, especially copper(II) complexes are frequently associated with pronounced antibacterial properties, the objective of the present study was the synthesis of novel thiosemicarbazone-based complexes and the evaluation of their antibacterial efficacy against Bacillus cereus.
In the present study, we report the synthesis of 2-benzoylpyridine N-(bicyclo[2.2.1]hept-2-yl)thiosemicarbazone (HL) and three corresponding copper(II) complexes: [Cu(L)NO3], [Cu(L)Cl], and [Cu(L)CHCl2COO]. The design of the ligand was based on a camphor-derived structural fragment, chosen due to the ability of such derivatives to display enhanced biological activity compared to their parent natural products. The thiosemicarbazone was prepared through a two-step synthetic procedure, followed by complexation reactions with appropriate copper(II) salts in ethanol in 1:1 molar ratio.
To evaluate the antibacterial activity of the obtained compounds against Bacillus cereus, the broth microdilution method was used. The HL did not exhibit activity, however, its copper(II) complexes demonstrated strong results, surpassing the activity of Furacillinum, an antimicrobial drug used in medicine. The most active compound is complex [Cu(L)NO3], with MIC and MBC values of 0.24 µg/mL, which is 20 times higher than the activity of Furacillinum.
This work was fulfilled with the financial support of the ANCD project 24.80012.5007.14TC.
