Polygodial is a sesquiterpene dialdehyde found in several plant species such as Polygonum hydropiper and Tasmannia lanceolata. There is some scientific evidence to support its antiparasitic effects, particularly against nematodes and other helminths. Laboratory studies have demonstrated that polygodial possesses significant anthelmintic activity in vitro. For example, research published in Veterinary Parasitology (2011) tested polygodial extracted from Tasmannia lanceolata against Haemonchus contortus, a parasitic nematode. The study found that polygodial inhibited larval development and motility at certain concentrations, suggesting a direct toxic effect on nematodes.

Other studies have supported these findings, showing that polygodial and plants rich in this compound can affect the survival and function of various parasitic worms in vitro. However, the majority of evidence comes from laboratory (in vitro) studies, with limited data from in vivo (animal or human) trials. Traditional use of polygodial-containing plants as anthelmintics is not well documented, so the scientific interest is driven primarily by laboratory findings rather than ethnobotanical practices.

In summary, while there is some scientific evidence—mainly from in vitro research—that polygodial has activity against nematodes and other parasites, robust clinical or in vivo evidence is lacking. Therefore, the overall evidence rating for its use as an antiparasitic agent is moderate but not strong.