Activity of diimidazoline amides against African trypanosomiasis

Identification and Structure-Activity Relationships of Novel Compounds that Potentiate the Activities of Antibiotics in Escherichia coli

In Gram-negative bacteria, efflux pumps are able to prevent effective cellular concentrations from being achieved for a number of antibiotics. Small molecule adjuvants that act as efflux pump inhibitors (EPIs) have the potential to reinvigorate existing antibiotics that are currently ineffective due to efflux mechanisms. Through a combination of rigorous experimental screening and in silico virtual screening, we recently identified novel classes of EPIs that interact with the membrane fusion protein AcrA, a critical component of the AcrAB-TolC efflux pump in Escherichia coli. Herein, we present initial optimization efforts and structure-activity relationships around one of those previously described hits, NSC 60339 (1). From these efforts we identified two compounds, SLUPP-225 (17h) and SLUPP-417 (17o), which demonstrate favorable properties as potential EPIs in E. coli cells including the ability to penetrate the outer membrane, improved inhibition of efflux relative to 1, and potentiation of the activity of novobiocin and erythromycin.

Antiprotozoal Selectivity of Diimidazoline N-Phenylbenzamides

We discovered three diimidazolines with high antiplasmodial selectivity that had IC50 values of 1.9-28 nM against cultured Plasmodium falciparum. We also identified a gem-dimethyl diimidazoline with high antitrypanosomal selectivity that had an IC50 value of 26 nM against cultured Trypanosoma brucei rhodesiense. Two 2-imidazoline heterocycles in a para orientation on a N-phenylbenzamide or similar core structure were required for high antiprotozoal activity. Ring expansion of the imidazoline as well as heterocyclic variants with pKa values of <7 all decreased activity significantly.