Synthesis and Antimicrobial Evaluation of Aminoguanidine and 3-amino- 1,2,4-triazole Derivatives as Potential Antibacterial Agents

A series of aminoguanidine derivatives bearing a 1,3,4-oxadiazole or piperazine moiety has been synthesized and fully characterized together with a series of 3-amino-1,2,4-triazole derivatives, and the resulting compounds were evaluated for their anti-bacterial activity. Most of these compounds showed broad-spectrum antibacterial activities against both Gram-positive and Gram-negative bacteria with minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) values in the range of 1–64 μg/mL, including multidrug-resistant clinical isolates and a fungus. Notably, compounds 19e and 19f exhibited higher levels of activity than gatifloxacin and moxifloxacin against several methicillin-resistant Staphylococcus aureus (3167 and 3506) and quinolone-resistant S. aureus (3505 and 3519) strains with MIC and MBC values in the range of 1–2 µg/mL. These two compounds also displayed significant antifungal activities with MIC values of 1 μg/mL against Candida albicans 7535, which were equivalent to the MIC value of the standard drug fluconazole. These results therefore indicate that aminoguanidine derivatives that do not contain a piperazine moiety are interesting scaffolds for the development of novel antibacterial agents.