Antiparasitic Effects and Cellular Mechanisms of Formononetin (a Natural Isoflavone) Against Hydatid Cyst Protoscoleces

Background: The chemical agents applied to reduce the complications of hydatid cyst surgery are not free of side effects. Formononetin (FMN), as a natural isoflavone, has been shown to have various therapeutic benefits. Objectives: We studied the in vitro and ex vivo protoscolicidal activity and cellular mechanisms of FMN against hydatid cyst protoscoleces. Methods: Formononetin at 75, 150, and 300 μg/mL was mixed with hydatid cyst protoscoleces (103/mL), and the viability was determined in 5 to 60 min through eosin staining assay. The effect of FMN on caspase-3 activity was tested through a commercial colorimetric protease kit. In addition, the penetrability of the plasma membrane of protoscoleces after exposure to FMN was also determined by the SYTOX assay. Results: Formononetin at 300 μg/mL completely destroyed hydatid cyst protoscoleces after 30 minutes. While at 150 μg/mL, after 60 minutes of contact, 100% of protoscoleces were eliminated. By ex vivo assay, FMN showed its antiparasitic effect for longer periods. Based on these results, FMN at 300 μg/mL concentration completely eliminated hydatid cyst protoscoleces after 60 minutes of exposure. While at a concentration of 150 μg/mL after 60 minutes, 89.6% of protoscoleces were destroyed. Formononetin noticeably increased (P < 0.001) the activity of caspase-3 and the permeability of protoscoleces dose-dependently. Conclusions: Formononetin as a natural product showed promising effects on the protoscoleces of hydatid cysts, indicating that it can be considered a valuable scolicidal agent. However, additional investigations are necessary to evaluate its efficacy in animal models and human subjects.