Molecular modeling study and synthesis of novel dicationic flexible triaryl guanidines and imidamides as antiprotozoal agents

A new series of fourteen dicationic flexible triaryl bis-guanidines 3a,b, bis-N-substituted guanidines 7a,b and 8a,b as well as bis-imidamides 9–12a,b having a 1,3- or 1,4-diphenoxybenzene scaffold backbone were synthesized. The in vitro activity of the novel dications as antiprotozoal agents against Trypanosoma brucei rhodesiense (T.b.r.) and Plasmodium falciparum (P.f.) was assessed. Interestingly, six of the newly synthesized dications viz3a,b, 7a,b and 8a,b were more active against P.f. than the reference drug pentamidine. Also, some of the dications showed moderate antitrypanosomal activity. Thermal melting analysis of the novel dications was performed to determine their ligand-DNA relative binding affinities. Finally, docking of the dications with an AT rich DNA oligonucleotide was executed to understand their binding mode with the minor groove.

Overlay of 7b (green) and pentamidine (red) showing their 2D binding interaction to the minor groove of the polydA.polydT DNA oligomer.Figure optionsDownload as PowerPoint slideHighlights
► Novel dicationic flexible triaryl guanidines and imidamides were synthesized.
► All the dications were tested against T.b.r. and P.f. and compared to pentamidine.
► The guanidiniums and imidamides displayed good in vitro antiplasmodial activity.
► Tm data and docking showed these dications to bind as monocations to DNA.