Argemone mexicana (Mexican poppy, Mexican prickly poppy, Flowering thistle, cardo or cardosanto) is a species of poppy found in Mexico and now widely naturalized in many parts of the world. An extremely hardy pioneer plant, it is tolerant of drought and poor soil, often being the only cover on new road cuttings or verges. It has bright yellow latex, and though poisonous to grazing animals, is rarely eaten, but has been used medicinally by many people including those in its native area, the Natives of the western US and parts of Mexico.
A. mexicana seeds contain 22–36% of a pale yellow non-edible oil, called argemone oil or katkar oil, which contains the toxic alkaloids sanguinarine and dihydrosanguinarine. Four quaternary isoquinoline alkaloids, dehydrocorydalmine, jatrorrhizine, columbamine, and oxyberberine, have been isolated from the whole plant of Argemone mexicana.
The seeds resemble the seeds of Brassica nigra (mustard). As a result, mustard can be adulterated by argemone seeds, rendering it poisonous. Several significant instances of katkar poisoning have been reported in India, Fiji, South Africa and other countries. The last major outbreak in India occurred in 1998. 1% adulteration of mustard oil by argemone oil has been shown to cause clinical disease.
Katkar oil poisoning causes epidemic dropsy, with symptoms including extreme swelling, particularly of the legs.
The Seri of Sonora, Mexico use the entire plant both fresh and dried. An infusion is made to relieve kidney pain, to help expel a torn placenta, and in general to help cleanse the body after parturition.
When the Spanish arrived in Sonora they added this plant to their pharmacopia and called it cardosanto, which should not be mistranslated to blessed thistle (Cnicus benedictus). Use in Hispanic cultures includes as a sedative and analgesic tea, including for use to help alleviate migraine headaches. The seeds are taken as a laxative.
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