Rapid detachment of Giardia lamblia trophozoites as a mechanism of antimicrobial action of the isoflavone formononetin.

OBJECTIVES Attachment to the small intestinal mucosa is crucial for initiating and maintaining Giardia infection. We tested the effect of isoflavones on Giardia attachment. METHODS We evaluated the effect of formononetin on trophozoite attachment to glass, to intestinal epithelial cell layers in vitro and to murine small intestinal explants, and on the intestinal load in mice. RESULTS We found that the isoflavone formononetin inhibits both attachment and flagellar motility within minutes and reduces the trophozoite load of Giardia in mice within 1.5 h after treatment. CONCLUSIONS The antigiardial activity of formononetin is at least partially due to its capacity to rapidly detach trophozoites.