Evaluation of antimicrobial activities of commercial herb and spice extracts against selected food-borne bacteria

  •  Anna Witkowska    
  •  Dara Hickey    
  •  Mercedes Alonso-Gomez    
  •  Martin Wilkinson    


The aim of this study was to evaluate and compare the antimicrobial properties of extracts of thirty commercial herbs and spices commonly used in the production of ready meals. Various extracts of spices were evaluated for their antimicrobial activities against Escherichia coli, Listeria innocua, Staphylococcus aureus and Pseudomonas fluorescens using a microdilution broth method. Ethanol and hexane extracts of oregano, clove, sage, rosemary and celery showed relatively strong antimicrobial activities against all bacteria tested. In contrast, water extracts displayed little or no antimicrobial activity. Flow cytometry revealed that cell membrane structures were damaged by spice and herb active extracts, while analysis of intra- and extracellular ATP contents of bacteria indicated that an increase in extracellular ATP was partially due to intracellular leakage. Extract combinations assessed using the checkerboard method did not display synergistic effects, however, some additive effects were observed when oregano was combined with sage or rosemary against L. innocua or S. aureus. This study has demonstrated that some commercial spice extracts have antimicrobial activity against food-borne bacterial species and may be considered as potential antibacterial agents for addition to ready meals.

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