Design, synthesis, antimicrobial evaluation, and molecular modeling of new sulfamethoxazole and trimethoprim analogs as potential DHPS/DHFR inhibitors

Abstract

Trimethoprim (TMP) and sulfonamides and are typically utilized to hinder the activities of dihydrofolate reductase (DHFR) and dihydropteroate synthase (DHPS) enzymes, respectively. In this context, we aimed to enhance the understanding of the inhibitory effects on dihydrofolate reductase (DHFR) and dihydropteroate synthase (DHPS) enzymes by synthesizing and evaluating two series of compounds. These compounds, designed as derivatives of p-aminobenzoic acid (related to sulfamethoxazole, SUL) and trimethoprim analogs, were rigorously tested for their in vitro antimicrobial efficacy and their ability to hinder the activities of DHFR and DHPS enzymes.Among the synthesized compounds, compounds 6 and 10 demonstrated exceptional antimicrobial efficacy against a diverse spectrum of bacterial and fungal strains. The assessment of these compounds also included their impact on biofilm formation, evaluated through crystal violet staining. Our in vitro enzyme assays revealed that compound 10 emerged as the most potent inhibitor of DHPS, with an IC50 value of 224.91 μg/mL, surpassing SUL by 1.6 times. Simultaneously, Compound 6 exhibited particularly potent DHFR-inhibitory action, with an IC50 value of 3.731 μg/mL, surpassing TMP by a factor of three.Molecular modeling studies further elucidated the mode of action, illustrating that compound 10 effectively occupied the DHPS pterin-binding site alongside p-aminobenzoic acid. In contrast, compound 6 was adeptly positioned within the DHFR-binding pocket.In summary, our findings underscore the promising prospects of compounds 6 and 10 in the management of bacterial infections. The results not only demonstrate their remarkable antimicrobial efficacy but also position them as potentially effective in a synergistic combination targeting the DHPS/DHFR enzymatic cascade.