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COMPARATIVE ANTIBACTERIAL PERFORMAMNCE OF FOUR ACYL-SUBSTITUTED PENICILLIN DERIVATIVES

Abstract

The increasing prevalence of beta-lactam antibiotic resistance shows the significance of developing different and improved derivatives of penicillin with better antibacterial properties. In this study, four acyl-modified penicillin derivatives were synthesized by using naphthoyl chloride, benzoyl chloride, cinnamoyl chloride, and hydrocinnamoyl chloride. The created compounds—naphthoyl-penicillin, benzoyl-penicillin, cinnamoyl-penicillin, and hydrocinnamoyl-penicillin—were evaluated for their antibacterial capabilities against two bacterial species commonly found: the Gram-negative Escherichia coli and the Gram-positive Staphylococcus epidermidis. The intention of this project was to determine whether modifications to the structure of the penicillin backbone would influence the antibacterial efficacy and if there were any derivative that had an improved performance compared to the standard penicillin. In the experiment, each derivative was tested at three dilutions (25, 38, 50 ppm) utilizing the Kirby-Bauer test of disk diffusion assays. The agar plates were inoculated with either E. coli or S. epidermidis, then the zones of inhibition were measured and compared to water controls, storebought penicillin, and storebought clindamycin. The water controls produced little to no inhibition, which confirmed the need for an active antibacterial, and clindamycin produced the largest zones overall, which validated the assay performance. Across both species of bacteria, naphthoyl-penicillin demonstrated the strongest antibacterial activity, consistently producing the largest zones of inhibition, even outperforming the commercially available penicillin. The hydrocinnamoyl-penicillin and benzoyl-penicillin showed moderate performance. Cinnamoyl-penicillin demonstrated the weakest antibacterial activity, producing the smallest zone across most of the trials. All derivatives showed more effectiveness against S. epidermidis than E. coli, which is expected considering the nature of these derivatives. Higher concentration levels did result in larger inhibition zones, but there was no consistent improvement in antibacterial performance as the concentration levels rose. Formal statistical analysis through a two-way ANOVA test will be completed in the full study to confirm the significance of the observed results.

Acknowledgements

Natural Science Honors Committee

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