Antibacterial effects of 30 new heterocyclic derivatives including thiazole, thiazolidine, imidazole, tetrahydropyrimidine, oxazolidine and thiazepine against some pathogenic Gram-positive and Gram-negative bacteria

The spread of drug-resistant microbial strains has been known as one of the main problems of world health in the last century. In addition, indiscriminate and arbitrary use of antibiotics is resulted to appear the side effects such as gastrointestinal discomfort, nausea, diarrhea and allergy. These factors have encouraged researchers to identify and use the novel antibacterial agents containing more powerful and broad-spectrum inhibitory effects, and fewer side effects. Thiazole, thiazolidine, imidazole, tetrahydropyrimidine, oxazolidine and thiazepine derivatives are the parts of the most important families of heterocyclic compounds that their various biological properties have been reported. In this study, the antibacterial effects of 30 new derivatives of these families have been investigated against the bacteria including Staphylococcus epidermidis, Streptococcus pyogenes, Bacillus thuringiensis, Salmonella typhi and Shigella flexneri.
After preparation of solution of derivatives in DMSO, in order to evaluate their antibacterial effects, inhibition zone diameters were measured via a disk diffusion method. Besides, the broth microdilution method was also used to determine the minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC). All effects have been compared to the antibiotics gentamicin and penicillin.
Inhibitory effects were observed only in some derivatives. Thiazole derivative 23 as the most effective compound had an inhibitory effect against all tested bacteria. Even though, imidazole derivative 3 had no inhibitory effect against Salmonella typhi, its effects against five bacterial strains were obviously identified more as well.
Inhibitory effects of various new heterocyclic derivatives against some standard bacterial strains were proved. In order to use these derivatives as antibiotic, their inhibitory effects should be evaluated on drug-resistant strains of these pathogens in the next step.