View photos of the medicinal (potentially toxic) plant Jatropha macrorhiza (Nettlespruge), profiled in Medicinal Plants of the American Southwest.

A passage from Medicinal Plants of American Southwest:

Jatropha macrorhiza has a similar array of tannins, but it also contains strongly purgative compounds. Liken its effect to very strong Rhubarb. Enough J. macrorhiza to provide a laxative effect will almost certainly elicit rebound constipation. Consider recognizing this species for its visual beauty and not as a medicine.