Background: The increase in prevalence of antimicrobial-resistant bacteria (ARB) is currently a serious threat, thus there is a need for new classes antimicrobial compounds to combat infections caused by these ARB. The growth inhibition ability of derivatives of the components of nucleic acids has been well-characterized but not for its antimicrobial characteristics. Aims: To evaluate in vitro antimicrobial activity profile of modified pyrimidine nucleosides derivatives. Methodology: Modified nucleosides arabinofuranosylcytosine (cytarabine, ara-C), [1-(2',3',5'-tri-O-acetyl-β-D-ribofuranosyl)-4-(1,2,4-triazol-1-yl)]uracil (TTU), and nucleotides cytarabine-5′-monophosphate (ara-CMP), and O2,2′-cyclocytidine-5′-monophosphate (cyclocytidine monophosphate, cyclo-CMP) were synthetized and subsequentially checked for antibacterial activity. Bacterial cells characteristics were assessed by antiproliferative and the production of intracellular reactive oxygen species (ROS) assays. Results: It was found that modified nucleosides ara-C, and TTU, and nucleotides ara-CMP, and cyclo-CMP were able to inhibit Escherichia coli, Sarcina lutea, Bacillus cereus, and Proteus mirabilis strains in a time and dose dependent manner via killing kinetics assay. Gram-negative (E. coli and P. mirabilis) bacteria stains were more sensitive to the exposure of TTU and cyclo-CMP and less sensitive to the exposure of ara-C and ara-CMP compared to gram-positive ones. The most effective cells growth inhibitor for gram-positive strains (S. lutea, B. cereus) was ara-CMP with ED50 = 5.2•10-5 M and 3.1•10-4 M, respectively. Sarcina lutea appeared to be the most sensitive bacteria strain to the exposure of all studied compounds. It was demonstrated that studied modified pyrimidine nucleosides derivatives enhanced the production of intracellular ROS over time (validated via DCFA-DA probe assay). Conclusion: This study has revealed the mechanism of action of cytarabine, cyclocytidine monophosphate, and TTU as an antimicrobial agent for the first time, and has shown that these pyrimidine derivatives enhanced might be able to combat infections caused by Escherichia coli, Sarcina lutea, Bacillus cereus, and Proteus mirabilis in the future.

Recently, it was postulated that antimicrobial substances kill bacteria by a common mechanism involving the formation of reactive oxygen species, in addition to particular drug-target interactions (ROS). However, there is a lot of controversy about this mechanism that produces hydroxyl radicals. Different experimental approaches are anticipated to be the root of the inconsistent results because the role of ROS to antibiotic-mediated death most likely varies on the circumstances. In the current work, the bacteria strains Escherichia coli, Sarcina lutea, Bacillus cereus, and Proteus mirabilis were treated with nucleoside-based compounds 2-F-araA, 2-F-araAMP and NH2-6-Cl-araPur, and the formation of reactive oxygen species (ROS) was measured. The formation of intracellular reactive ROS was shown to be increased over time by the examined modified pyrimidine nucleoside derivatives (validated via DCFA-DA probe assay). For instance, an increase in the ROS was measured in E. coli after treatment with NH2-6-Cl-araPur  but not after treatment with 2-F-araA, and2-F-araAMP. Results also vary depending on the species studied and the experimental setup. Despite this, our data strongly imply that using antioxidants as therapeutic agents to treat some infections is a viable option that is starting to be used against bacterial strains.

Toxicological asessment of a dietary supplement based on erbium and europium chlorides by intragastric administration to white rats.