The effects of saturated fatty acids on Giardia duodenalis trophozoites in vitro

Parasitol Res. 2005 Oct;97(3):191-200. doi: 10.1007/s00436-005-1432-5. Epub 2005 Jul 1.


Giardia duodenalis is a protozoal, intestinal parasite that is a common aetiological agent of infectious diarrhoea in humans worldwide. Chemotherapeutic intervention presently offers a limited range of drugs and these are usually only employed after clinical diagnosis. Moreover, these drugs are ineffective against the infectious cysts, can produce unpleasant side effects, and are expensive with limited availability in developing countries. Frequent reports of drug toxicity, treatment failure and parasite drug resistance have, in some instances, also resulted in the increasing reluctance to over-prescribe synthetic anti-microbials. Alternatively, there is now mounting evidence to suggest that some of the naturally derived, medium-chain, saturated fatty acids (MCSFAs) possess anti-microbial and anti-parasitic properties. We have therefore examined the effects of four different fatty acids on G. duodenalis trophozoites in vitro. Cytotoxicity was determined using fluorescence, scanning and transmission electron microscopic techniques and standard cytotoxicity assays. Our studies have confirmed that the MCSFA, dodecanoic acid (C: 12) (common name: lauric acid), is anti-giardial, with an LD50 concentration comparable to that of metronidazole, the drug of choice in the treatment of giardiasis. Dodecanoic acid appeared to induce trophozoite death by accumulating within the parasite cytoplasm resulting in rupture of the cell membrane. This study has opened fresh avenues for development of natural drug therapy in which food supplementation may augment, or even replace, some of the standard chemotherapeutic agents presently employed in the treatment of giardiasis and possibly other infectious intestinal diseases.

MeSH terms

  • Animals
  • Antiprotozoal Agents / pharmacology*
  • Caprylates / pharmacology
  • Decanoic Acids / pharmacology
  • Dose-Response Relationship, Drug
  • Fatty Acids / pharmacology*
  • Giardia / drug effects*
  • Giardia / growth & development
  • Giardia / ultrastructure
  • Giardiasis* / drug therapy
  • Giardiasis* / parasitology
  • In Vitro Techniques
  • Inhibitory Concentration 50
  • Lauric Acids / pharmacology
  • Longevity / drug effects
  • Microscopy, Electron, Scanning
  • Microscopy, Electron, Transmission
  • Microscopy, Fluorescence
  • Palmitic Acid / pharmacology
  • Parasitic Sensitivity Tests


  • Antiprotozoal Agents
  • Caprylates
  • Decanoic Acids
  • Fatty Acids
  • Lauric Acids
  • lauric acid
  • Palmitic Acid
  • decanoic acid
  • octanoic acid