Let’s conclude the medicinal plant diversity series with a species originating in Mesoamerica. Today’s photographs are courtesy of Forest & Kim Starr, the photographers behind many of the images on the Hawaiian Ecosystems at Risk project. These images, plus many more, can be found on the photographs page for Dysphania ambrosioides (here labeled under a synonym, Chenopodium ambrosioides).
As implied above, Dysphania ambrosioides has readily spread (in some places, invasive) from its native southern North America to northern South America range to tropical and warm-temperate regions around the world (modern distribution in northern North America). Common names abound for the species, ranging from American wormseed to paico (Peru) and epazote (Latin America) to erva de Santa Maria (Brazil).
Dysphania ambrosioides has the quality of being both a spice and a traditional medicinal herb. Gernot Katzer’s excellent Spice Pages has the details on epazote as a leafy herb, including its common names in 32 languages and its use in Mexican cuisine for foods such as refried beans (added due to its antiflatulent properties).
On the medicinal side–and in addition to its use as an antiflatulent–wormseed or wormwort was long-used globally as an antihelminthic, a drug that helps expel intestinal worms. The most medicinally active compound in Dysphania ambrosioides is ascaridole, present in its oil. In particular, there is a cultivated type of Dysphania ambrosioides known as Chenopodium ambrosioides var.? subsp.? anthelminticum (or sometimes Chenopodium anthelminticum) that is grown for its high concentrations of the chemical in the seed oil (the taxonomy is very uncertain here, not sure if the cultivated type is botanical or horticultural in origin). Use of Dysphania ambrosioides as an antihelminthic, however, declined significantly in the 1930s as less toxic medicines for treatment were developed, retreating from mainstream use in Europe, North America and South America to only being used significantly as a traditional medicine in its native Mesoamerica.
Cornell University’s Medicinal Plants for Livestock: Dysphania ambrosioides gives an excellent account of the history of the species in cultivation and discusses the extreme toxicity of the oil (2 teaspoons of the oil can kill or adversely effect an adult sheep). It also warns “The dose that causes adverse effects is very close to the dose that is supposed to be efficacious. Therefore, extreme caution should be used when treating an animal with this plant or the oil made from the plant.”. It should also be noted that in high concentrations, it is used as an insecticide.
Few references mention this, but the species has also received a recent examination as a candidate drug for cancer treatment: see Efferth, T. et al. 2002. Activity of ascaridol from the anthelmintic herb Chenopodium anthelminticum L. against sensitive and multidrug-resistant tumor cells. Anticancer Res. 22(6C):4221-4.