Investigation of antimicrobial activities of indole-3-aldehyde hydrazide/hydrazone derivatives.

Indoles and hydrazone-type compounds constitute an important class of compounds for new drug development in order to discover an effective compound against multi-drug-resistant microbial infections. A series of indole-3-aldehyde and 5-bromoindole-3-aldehyde hydrazide and hydrazones was evaluated for their in vitro antimicrobial activities using the 2-fold serial dilution technique against Staphylococcus aureus, methicillin-resistant S. aureus (MRSA), Escherichia coli, Bacillus subtilis and Candida albicans. The minimum inhibitory concentration (MIC) was determined for test compounds and for the reference standards sultamicillin, ampicillin, fluconazole and ciprofloxacin. Compounds possessed a broad spectrum of activity having MIC values of 6.25-100 mg/ml against the tested microorganisms. Compounds 1a-1j, in particular, displayed better activity against MSRA and significant activity against S. aureus relative to ampicillin. Unexpectedly, indole nicotinic acid hydrazides showed no significant activity while indole anisic acid hydrazides displayed better activity. The results may be instructive to researchers attempting to gain more understanding of the antimicrobial activity of indole hydrazide/hydrazone-type compounds.