Oregano (Lippia spp.) kills Giardia intestinalis trophozoites in vitro: antigiardiasic activity and ultrastructural damage

Parasitol Res. 2006 May;98(6):557-60. doi: 10.1007/s00436-005-0082-y. Epub 2006 Jan 20.


In the world, giardiosis is still a very important parasitic disease; only in Asia, Africa and America, there are more than 200 million of infected people in a year. The usual treatments are drugs that produce undesirable secondary effects, perhaps favouring the resistant strain selection. One alternative is to research compounds from plants used as antidiarrhoeic or antiparasitic in the traditional medicine. In a previous work, we found that Lippia beriandieri (Oregano) revealed to be more potent than tinidazole, a common antigiardiasic drug. In this current work, we tested the cell viability by re-culture and reduction of MTT-tetrazolium salts to MTT-formazan, and we showed the effect of oregano ethanolic extracts against Giardia intestinalis (synonyms: Giardia duodenalis, Giardia lamblia) trophozoites at concentrations ranging form 58 to 588 microg. We demonstrated the ultrastructural injury produced by oregano extracts in this parasite. Trophozoites lost their size and shape and showed damage in nucleus structure, perhaps by breaking the pattern of nucleoskeleton proteins.

MeSH terms

  • Animals
  • Antiprotozoal Agents / pharmacology*
  • Cell Nucleus / ultrastructure
  • Cell Survival
  • Giardia lamblia / drug effects*
  • Giardia lamblia / ultrastructure*
  • Humans
  • Microscopy, Electron, Transmission
  • Origanum* / chemistry
  • Plant Extracts / pharmacology*
  • Staining and Labeling
  • Tetrazolium Salts / metabolism
  • Thiazoles / metabolism
  • Trophozoites / drug effects*


  • Antiprotozoal Agents
  • Plant Extracts
  • Tetrazolium Salts
  • Thiazoles
  • thiazolyl blue