Stories: Curse of The 'Mexican' Poppy

 

The Mexican poppy (Argemone mexicana, Papaveraceae)

Today, I'm telling you a true horror story behind a lethal plant of the poppy family (Papaveraceae), the Mexican poppy (Argemone mexicana). It is responsible for tens of thousands of human poisoning events, a debilitating disease called epidemic dropsy. 

To begin with, the Mexican poppy isn’t even Mexican, it most likely originated from the West Indies (Antilles), but was introduced to the harbours of Mexico. This genus and species were described by a French botanist named Joseph Tournefort in 1694. The Latin name ‘Argemone’ is Greek for a herbal remedy claimed by Hippocrates to cure eye ailments. This naming however, would later prove to be disastrous! In the coming 300 years, the ‘Mexican’ poppy was introduced to nearly all tropical and subtropical regions of the world, including parts of Africa, India and Australia. In fact, A. mexicana is highly adaptable to a wide range of habitats, it is tolerant of cold, heat, drought and poor soil. The seeds of A. mexicana can remain viable for ten to twenty years, forming a permanent seed bank on the ground. In its native range, A. mexicana is called ‘Chicalotl’ (translates as ‘the prickly one’), and its flowers were used by American Indians for their slightly narcotic property.

Argemone mexicana flower

Soon after A. mexicana was described, the Portuguese thought that it has wonderful medicinal effects, and introduced the species to East Africa around 1800s. The ‘Mexican’ poppy probably conquered India via Goa. The seedpod of A. mexicana looks remarkably similar to that of the Datura, and as a result the Indians most likely accepted Argemone as a sacred medicinal plant. They even incorporated Argemone as a treatment for eye diseases into Ayurveda! Little did the Indians knew this miraculous herb ‘Argemone’ would bring disasters of epidemic proportion all across India.

In 1870s, huge outbreaks of a mysterious disease started affecting tens of thousands of people in India. At times, there were thousands of fatalities, mainly malnourished children. An eminent military surgeon at the time, colonel Kenneth McLeod first described the condition in the journal [Nature] in 1894, and his descriptions were so accurate, they still hold true today. McLeod coined the term ‘epidemic dropsy’ and in his own words, “The leading symptoms of the disease was anasarca (massive swelling of the whole body, especially the limbs), preceded or accompanied by fever, vomiting, diarrhea, and sometimes irritation of the skin; it was often accompanied by exanthematous eruption (reddish rashes), deep seated pain in the limbs, dyspnoea (difficulty breathing), progressive anemia, and not infrequently by hydropericardium (hepatitis), hydrothorax (fluid in the chest), or oedema (swelling) of the lungs. The disease ran its course in from three to six weeks, and had a mortality of 2 to 40 per cent, death being brought about, often suddenly, by heart failure or by lung complications.’’ Epidemic dropsy was also known to cause severe glaucoma and permanent blindness in some patients. However, none of the medical professionals had any clue as to the cause of epidemic dropsy. They suspected that the disease was caused by an unknown pathogen or perhaps some form of vitamin deficiency. But one thing was certain, epidemic dropsy always affected the poor and malnourished.

 

Excerpt (top right) showing colonel Kenneth McLeod's original description of epidemic dropsy. One can imagine how terrifying was the situation when people really had no idea what was happening to them, and what was causing the disease! Br Med J 1893;2:1053. Doi: 10.1136/bmj.2.1715.1053

Eventually, it was the Indian villagers themselves who figured out the root cause of epidemic dropsy. Health officials were told that the disease ensued when cooking oil was contaminated by the seed oil of Argemone mexicana, the ‘Mexican’ poppy. Research and autopsies were carried out on experimental animals and humans (dead or alive), and the cause was conclusive. The seed oil of A. mexicana was subjected to extensive chemical investigation, leading to the isolation of two main alkaloid toxins called sanguinarine and dihydrosanguinarine. The alkaloid concentration could be as high as 0.4 – 2% volume/ volume argemone oil. When tested on animals, both alkaloids showed marked toxicity leading to death within 48 hours. Sanguinarine was found to be at least twice as toxic as its dihydro-congener, and it was identified as the principle toxic component of argemone oil. It was later proven that in the impoverished regions of India, people often adulterated cooking oil with argemone oil to reap benefit. Despite extensive law enforcement and public awareness campaign, this is still a problem today. 

 

Argemone mexicana seeds

Even today, the pathophysiology or mechanism of action of sanguinarine in causing epidemic dropsy is not completely understood. However, sanguinarine would turn out to be a poison of multiple actions, and to understand how sanguinarine works, or if there is an antidote, we have to examine the chemistry behind this remarkable toxin. For that, we will look into its [Science].