Aqueous medium synthesis, characterization and evaluation of the antioxidant and antibacterial activities of new pyrimidine-and purine-ligated pyrrole

A new pyrimidine- and purine-ligated pyrrole were synthesized through the Hantzsch multicomponent reaction using nucleobases (cytosine, adenine or guanine) as amine nucleophiles in water as solvent. The structures of the synthesized compounds were elucidated through proton (¹H) and carbon (¹³C) nuclear magnetic resonance (NMR) and Fourier-transform infrared (FT-IR) spectroscopy, mass spectrometry, and elemental analysis. The total antioxidant capacity (TAC) of the products was evaluated by the phosphomolybdenum assay. The in vitro antioxidant activity of the target compounds was assessed using 2,2-diphenyl-1-picrylhydrazyl (DPPH•) and 2,2′-azino-bis(3-ethylenzothiazoline-sulfonic acid) diammonium salt (ABTS+•) free radicals. Compound 2c displayed the highest antioxidant activity against DPPH with IC50 of 6.55 μg/mL, and 3c exhibited the highest antioxidant activity against ABTS with IC50 of 18.37 μg/mL. Furthermore, the in vitro antibacterial properties of these compounds was assessed against Escherichia coli ATCC 25922, Pseudomonas aeruginosa ATCC 27853, Klebsiella pneumonia ATCC 13883 (Gram-negative: G-), and Staphylococcus aureus ATCC 25932 (Gram-positive: G+) bacterium, and compared with Gentamicin used as reference antibiotic. Compound 2a exhibited good antibacterial activity against Klebsiella pneumonia with inhibition zone of 17 mm. Compound 3a also showed a good antibacterial effect against E. coli taxon with inhibition zone of 18.5 mm relative to Gentamicin (20 mm). KEY WORDS: Antibacterial activity, Antioxidant activity, Hantzsch synthesis, Nitrogenous bases, Pyrrole Bull. Chem. Soc. Ethiop. 2025, 39(6), 1185-1200. DOI: https://dx.doi.org/10.4314/bcse.v39i6.13