Antiviral efficacy and mechanisms of action of oregano essential oil and its primary component carvacrol against murine norovirus

J Appl Microbiol. 2014 May;116(5):1149-63. doi: 10.1111/jam.12453. Epub 2014 Feb 12.


Aims: To investigate the antiviral efficacy of oregano oil and its primary active component, carvacrol, against the nonenveloped murine norovirus (MNV), a human norovirus surrogate.

Methods and results: Along with an observed loss in cell culture infectivity, the antiviral mechanisms of action were determined in side-by-side experiments including a cell-binding assay, an RNase I protection assay and transmission electron microscopy (TEM). Both antimicrobials produced statistically significant reductions (P ≤ 0·05) in virus infectivity within 15 min of exposure (c. 1·0-log10). Despite this, the MNV infectivity remained stable with increasing time exposure to oregano oil (1·07-log10 after 24 h), while carvacrol was far more effective, producing up to 3·87-log10 reductions within 1 h. Based on the RNase I protection assay, both antimicrobials appeared to act directly upon the virus capsid and subsequently the RNA. Under TEM, the capsids enlarged from ≤35 nm in diameter to up to 75 nm following treatment with oregano oil and up to 800 nm with carvacrol; with greater expansion, capsid disintegration could be observed. Virus adsorption to host cells did not appear to be affected by either antimicrobial.

Conclusions: Our results demonstrate that carvacrol is effective in inactivating MNV within 1 h of exposure by acting directly on the viral capsid and subsequently the RNA.

Significance and impact of the study: This study provides novel findings on the antiviral properties of oregano oil and carvacrol against MNV and demonstrates the potential of carvacrol as a natural food and surface (fomite) sanitizer to control human norovirus.

Keywords: human norovirus; mechanism of action; nonenveloped viruses; plant antimicrobials; sanitizer.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Animals
  • Antiviral Agents / pharmacology*
  • Cell Line
  • Cymenes
  • Mice
  • Monoterpenes / pharmacology*
  • Norovirus / drug effects*
  • Norovirus / ultrastructure
  • Oils, Volatile / pharmacology*
  • Origanum / chemistry*


  • Antiviral Agents
  • Cymenes
  • Monoterpenes
  • Oils, Volatile
  • carvacrol