Bellarmine University ScholarWorks@Bellarmine Undergraduate Theses Undergraduate Works 4-24-2020 Screening a Library of Chalcone Derivatives for Antibacterial Properties via Kirby Bauer Disk Diffusion Breena Z. Frazier Bellarmine University, [email protected] Follow this and additional works at: https://scholarworks.bellarmine.edu/ugrad_theses Part of the Chemicals and Drugs Commons Recommended Citation Frazier, Breena Z., "Screening a Library of Chalcone Derivatives for Antibacterial Properties via Kirby Bauer Disk Diffusion" (2020). Undergraduate Theses. 44. https://scholarworks.bellarmine.edu/ugrad_theses/44 This Honors Thesis is brought to you for free and open access by the Undergraduate Works at ScholarWorks@Bellarmine. It has been accepted for inclusion in Undergraduate Theses by an authorized administrator of ScholarWorks@Bellarmine. For more information, please contact [email protected], [email protected]. Frazier 1 Screening a Library of Chalcone Derivatives for Antibacterial Properties via Kirby Bauer Disk Diffusion Breena Frazier Spring 2020 A Senior Honors Thesis Presented in Partial Fulfillment of the Requirements of the Bellarmine University Honors Program Advisor: Dr. Amanda Krzysiak Reader: Dr. Savita Chaurasia Reader: Dr. Mary Huff Frazier 2 TABLE OF CONTENTS LIST OF FIGURES ................................................................................................... 4 LIST OF TABLES ..................................................................................................... 4 ABSTRACT ............................................................................................................... 6 INTRODUCTION ..................................................................................................... 7 Natural Products.......................................................................................................................... 7 Classification........................................................................................................................... 8 Chalcones .................................................................................................................................... 9 Chalcone Biosynthesis and Modification ............................................................................. 10 Biological and Pharmaceutical Properties ............................................................................ 10 Antimicrobials........................................................................................................................... 11 Antibiotics ............................................................................................................................. 11 Mechanisms of Action .......................................................................................................... 11 Antibiotic Resistance ............................................................................................................ 13 Antimicrobial Properties of Chalcone Derivatives ............................................................... 15 METHODS ..............................................................................................................17 RESULTS ................................................................................................................20 Gram Positive Strains ............................................................................................................... 23 Gram Negative Strains .............................................................................................................. 23 DISCUSSION ..........................................................................................................25 ACKNOWLEDGEMENT .......................................................................................29 LITERATURE CITED ............................................................................................30 APPENDIX A – ZONE OF INHIBITION MEASUREMENTS ............................34 TABLE 4. Zone of Inhibition Measurements for S. pneumoniae ............................................. 34 TABLE 5. Zone of Inhibition Measurements for S. enteritidis ................................................ 37 TABLE 6. Zone of Inhibition Measurements for B. subtilis .................................................... 40 TABLE 7. Zone of Inhibition Measurements for E. coli .......................................................... 44 APPENDIX B – PHOTOS OF AGAR PLATES POST-INCUBATION SHOWING ZONE OF INHIBITION ......................................................................47 Frazier 3 TABLE 8. Post-chalcone diffusion photographs of S. pneumoniae grown on Tryptic Soy Agar with 5% Sheep Blood after 24-36-hour Incubation at 37° C .................................................... 47 TABLE 9. Post-chalcone diffusion photographs of S. enteritidis grown on LB agar after 24- 36-hour incubation at 37° C ...................................................................................................... 51 TABLE 10. Post-chalcone diffusion photographs of B. subtilis grown on LB agar after 24-36- hour incubation at 30° C ........................................................................................................... 55 TABLE 11. Post-chalcone diffusion photographs of E. coli grown on LB agar after 24-36-hour incubation at 37° C ................................................................................................................... 60 Frazier 4 LIST OF FIGURES Figure 1. 1,3-Diphenylprop-2-en-1-one. Figure taken from Das, et al. .......................................... 9 Figure 2. Reaction Scheme for the Synthesis of Chalcones via Claisen-Schmidt Condensation. Figure taken from Durairaj M., et al. ............................................................................................ 10 Figure 3. Full library of chalcone compounds synthesized by Tucker, et al. ............................... 17 Figure 4. Disk Placement for Disk Diffusion (Anterior view) ..................................................... 19 Figure 5. Gram-positive bacteria growing on agar plates with chalcones showing mild bacterial inhibition. ..................................................................................................................................... 23 Figure 6. Gram-negative bacteria growing on agar plates with chalcones showing mild bacterial inhibition. ...................................................................................................................................... 23 Figure 7. Licochalcone A. ............................................................................................................. 27 LIST OF TABLES Table 1. Bacterial Growth Conditions. ......................................................................................... 18 Table 2. Results from SciFinder Literature Survey ...................................................................... 20 Table 3. Antibacterial activity of chalcones against three bacterial strains .................................. 21 Table 4. Zones of Inhibition for S. pneumoniae ........................................................................... 34 Table 5. Zones of Inhibition for S. enteritidis ............................................................................... 37 Table 6. Zones of Inhibition for B. subtilis ................................................................................... 40 Table 7. Zones of Inhibition for E. coli ........................................................................................ 44 Table 8. Post-chalcone diffusion photographs of S. pneumoniae grown on Tryptic Soy Agar with 5% Sheep Blood after 24-36-hour Incubation at 37° C ................................................................ 47 Table 9. Post-chalcone diffusion photographs of S. enteritidis grown on LB agar after 24-36-hour incubation at 37° C ....................................................................................................................... 51 Frazier 5 Table 10. Post-chalcone diffusion photographs of B. subtilis grown on LB agar after 24-36-hour incubation at 30° C ....................................................................................................................... 55 Table 11. Post-chalcone diffusion photographs of E. coli grown on LB agar after 24-36-hour incubation at 37° C ....................................................................................................................... 60 Frazier 6 ABSTRACT As antibiotic resistance emerges stronger than ever, novel antimicrobial compounds are necessary to continue the infectious fight against disease and prevent millions of deaths by multidrug-resistant bacteria. One compound thought to be a natural source of antimicrobial activity is the chalcone. Abundant in fruits and vegetables, chalcones are versatile compounds that are easily synthesized via Claisen-Schmidt condensation and have demonstrated a wide- range of biological activity. Previous studies have found that the addition of a free hydroxyl group to either the A or B ring of the chalcone skeleton may contribute to mild to moderate antimicrobial activity. Halogen substituents, such as bromine, chlorine, and fluorine, were also reported to aid in antibacterial activity. In this study, twenty chalcone compounds, fourteen of which had never been screened, were assessed for their antibacterial potential against two Gram- negative and two Gram-positive strains of bacteria.