Evaluation of the antimicrobial potential of chosen flavonoids on E. coli and S. aureus

Ida Axholm, Rooshanie Ejaz, Amanda Borup Jakobsen, Julia Poniewierska, Kasper Ranum & Josh Shailes

Student thesis: Termpaper


Due to selective pressure conferred by traditional antibiotic treatment, incidence of pathogenic antibiotic resistance continues to present as increasing problem. Many flavonoids have been found to have antibacterial effects and synergy between flavonoids, and between flavonoids and antibiotics have been found for some combinations. The flavonoids Quercetin, Morin, Naringenin and Dihydrokaempferol were tested for activity against the bacterial strains S. aureus ATCC 29213 and E.coli ATCC 25922. Using the spot-on method, MIC values for Quercetin, Morin and Naringenin were established against E. coli at 2, 4.5 and 3 mg/mL respectively and at 2.5, 10 and 10 mg/mL respectively against S. aureus. No inhibition was shown for either strain with Dihydrokaempferol for concentrations up to 7.5mg/mL. Combinatorial tests were performed for both strains using Quercetin plus Morin, Quercetin plus Naringenin and Morin plus Naringenin. FIC index (FICI) values were calculated in order to determine synergistic, additive or antagonistic effects of the different combinations. Strong synergism (FICI <0.6) was found for all combinations against E. coli and mild synergism was found against S. aureus for Naringenin plus Morin (FICI = 0.7). Possible additive effects were found for other combinations against S. aureus, though more testing may further elucidate combinatorial effects for these. Results indicate that due to synergistic effects there could be potential for using combination of flavonoids to manage E.coli infections and possibly limit the usage of antibiotics, and subsequently the incidence of antibiotic resistance.

EducationsMolecular Biology, (Bachelor/Graduate Programme) Undergraduate or graduate
Publication date30 Jun 2015


  • Antimicrobial
  • Dihydrokaempferol
  • FIC
  • Naringenin
  • Morin
  • MIC
  • Broth dilution
  • Flavonoids
  • Antibiotic
  • S. aureus
  • Quercetin
  • E. coli
  • Spot-on