Activity of calix [4] pyrrole derivatives against E. coli, S. aureus, and Streptococcus mutans as a novel antibacterial treatment

Background: The rapid emergence of antibiotic-resistant bacteria has become a global health crisis. The misuse of antibiotics in clinical and agricultural settings has accelerated the resistance of pathogenic bacteria, rendering many conventional treatments ineffective. Among the most concerning pathogens are Escherichia coli, Staphylococcus aureus, and Streptococcus mutans, which are linked to severe infections and increased resistance. This experimental study aims to evaluate the antibacterial activity of Calix[4]Pyrrole derivatives by assessing their inhibition zones and Minimum Inhibitory Concentration (MIC) against E. coli, S. aureus, and Streptococcus mutans, compared to the standard antibiotic Ampicillin.Methods:The derivatives were synthesized following standard protocols and characterized using Fourier Transform Infrared (FT-IR) spectroscopy and Nuclear Magnetic Resonance (NMR) spectroscopy to confirm their chemical structure. Antibacterial activity was evaluated using the Mueller-Hinton Agar (MHA) medium and the Kirby-Bauer well agar diffusion method. Zones of inhibition were measured after incubating the plates at 37°C for 24 hours. Minimum Inhibitory Concentration (MIC) values were determined by preparing serial dilutions of the compounds ranging from 15.6 to 500 µg/mL and monitoring bacterial growth.Results:The calix[4]pyrrole derivatives exhibited antibacterial activity against Staphylococcus aureus, Streptococcus mutans, and E. coli, with inhibition zones increasing as concentration increased. Calix[4] pyrrole derivative(Cpd3) showed the highest inhibition zones, up to 19.5 mm for Staphylococcus aureus.The MIC values confirmed that (Cpd3) had the lowest MIC across all bacteria,indicating its high efficacy. Calix[4] pyrrole derivative(Cpd4) also demonstrated strong antibacterial activity,particularly against E. coli.All compounds outperformed the standard antibiotic,Ampicillin.Conclusions: Calix[4] pyrrole derivatives show promise as alternative antibacterial agents and warrant further investigation for clinical applications.