Novel approach to combat antibiotic resistance: evaluation of some Armenian herb crude extracts for their antibiotic modulatory and antiviral properties

J Appl Microbiol. 2019 Aug;127(2):472-480. doi: 10.1111/jam.14335. Epub 2019 Jun 26.


Aims: One of the strategies to combat antibiotic resistance can be the use of plant materials in combination with antibiotics, taking into account that phytochemicals can act as antibiotic resistance-modifying agents. This can give a second life to the traditional antibiotics. The aim was to evaluate antibiotic modulatory effect of crude extracts from Agrimonia eupatoria, Hypericum alpestre, Rumex obtusifolius and Sanguisorba officinalis herbs towards several commercial antibiotics using some Gram-positive and Gram-negative bacteria.

Methods: The antibiotic modulatory activity was tested by determining MICs of antibiotics in the absence and presence of plant crude extracts at subinhibitory concentrations. Antiviral potential of different extracts of tested plant materials was also explored by double overlay plaque assay.

Results: The tested plant crude extracts exhibited high modulatory activity towards used antibiotics. Particularly, high modulatory activity was observed with extracts of H. alpestre and R. obtusifolius. Many plant-antibiotic combinations induced the decrease in MICs of antibiotics up to ~fourfold indicating synergy. Moreover, the similar change was observed at both subinhibitory concentrations (MIC/2 and MIC/4) of the same plant crude extract. High anti-phage activity of plants with the exception of Lilium armenum against T4 phage of Escherichia coli C-T4 was also shown.

Conclusions: Plant crude extract or commercial antibiotic combinations significantly increased the efficiency of antibiotics. Tested plant materials with exception of L. armenum have antiviral property.

Significance and impact of the study: For the first time, antibiotic modulatory activity of tested herb extracts was shown, which could have potential in practical applications. Tested plant materials with exception of L. armenum could have prospective, as a source of new antiviral compounds.

Keywords: Antibiotic modulatory activity; Armenian flora; antibiotics; antiviral activity; plant crude extracts.

MeSH terms

  • Anti-Bacterial Agents / pharmacology*
  • Antiviral Agents / pharmacology*
  • Armenia
  • Drug Resistance, Bacterial
  • Drug Synergism
  • Gram-Negative Bacteria / drug effects
  • Gram-Positive Bacteria / drug effects
  • Plant Extracts / pharmacology*
  • Plants, Medicinal


  • Anti-Bacterial Agents
  • Antiviral Agents
  • Plant Extracts