Antimicrobial activity of a series of thiosemicarbazones and their ZnII and PdII complexes

Thirty-four thiosemicarbazones andS-alkyl thiosemicarbazones, and some of their ZnII and PdII complexes were obtained and purified to investigate antimicrobial activity. MIC values of the compounds were determined by the disc diffusion method againstEscherichia coli, Klebsiella pneumoniae, Proteus mirabilis, Pseudomonas aeruginosa, Salmonella typhi, Shigella flexneri, Staphylococcus aureus, S. epidermidis, andCandida albicans. The thiosemicarbazones show antibacterial and antifungal effects in free ligand and metal-complex form. Picolinaldehyde-S-methyl- and -S-benzylthiosemicarbazones did not affect the tested microorganisms but their ZnII complexes showed selective activity. The antimicrobial activity is relatively high in Me2SO, but the antimicrobial potential is changed in a certain range with Me2SO, HCONMe2, EtOH and CHCl3.