Orellanine - How normal-looking mushrooms can be way poisonous

Orellanine is a nephrotoxic (nephros is Greek for kidney, you do the math) dipyridine possessing positively charged nitrogen atoms that is produced by several species of mushrooms belonging to the genus Cortinarius. Members of this genus are gilled mushrooms that grow in association with plants (i.e. are mycorrhizal) and have their gills protectively covered by a cottony cortina (veil or curtain, not to be confused with the Google Image-hogging vehicle of the same name) that spans between their pileus (cap) and stipe (stem) when they are but wee little shroomies. Known producers of the toxin include C. rubellus (deadly webcap), C. orellanus (fool's webcap), and a bunch more. Some of these are found in Europe, others in North America (most commonly in the fall), meaning that no one in the Western world is safe. These poisonous species are occasionally confused with edible or psychedelic mushrooms, resulting in sweet, sweet natural selection.

It has been estimated that the consumption of only 100 grams (about 3.5 ounces) of fresh C. orellanus is necessary to utterly destroy ones' kidney! Orellanine kills people by accumulating in the renal tubules of their kidneys and somehow selectively damaging this part of the organs to the point that they stop working (acute renal failure), an event that usually takes two to three weeks after the onset of symptoms to occur (okay, make that delayed acute renal failure). Unusually, the onset of symptoms (initially and unfortunately flu-like in nature) is typically delayed up to 3 to 4 days after mushroom consumption in severe cases, and up to three weeks in milder cases. If they don't die outright, about one-third to half of all those poisoned by orellanine develop chronic renal failure and may require dialysis or kidney transplant.

Like aflatoxins, which are mycotoxins produced by Aspergillus moulds that rank among the most carcinogenic chemicals known to man, orellanine is fluorescent, making it a blast at glow-in-the-dark mini putt. Similarly-structured substances include the herbicides paraquat and diquat, which are both toxic to humans. Paraquat is particularly nasty, accumulating in and causing progressive destruction of the lungs in a manner similar to how orellanine savages the kidneys.

- Berger KJ, Guss DA. Mycotoxins revisited: Part II. J Emerg Med. 2005 Feb;28(2):175-83. Review.
- Nilsson UA, Nyström J, Buvall L, Ebefors K, Björnson-Granqvist A, Holmdahl J, Haraldsson B. The fungal nephrotoxin orellanine simultaneously increases oxidative stress and down-regulates cellular defenses. Free Radic Biol Med. 2008 Apr 15;44(8):1562-9. Epub 2008 Jan 31.


Agaritine - Raw button mushrooms and The Cancer

Ah, the dichotomy of mycophagy. That statement sounded pretty darn impressive, didn't it? Admit it, you were a little impressed. Morels, truffles, and king boletes are arguably among the most saporous and sought-after foods out there, while false morels, Amanitas (which include the aptly-named Death cap and Destroying angel), and the Lethal webcaps will generally kill you if you eat them.

Then there's the genus Agaricus. It includes a number of species known to be at least mildly poisonous, as well as several others that are consumed around the world on a daily basis. The common store mushroom, Agaricus bisporus, also known as the commercial mushroom and the button mushroom, is by far the most popular of these, with hundreds of millions of the little guys being produced and consumed annually. The cream-coloured bundle of succulence (yeah, you read that right) that is sold today is actually a mutant strain discovered in Pennsylvania in 1926. The original cultivated strain was a light brown, but at the time white was very trendy. Another familiar strain of A. bisporus is the Portobello mushroom, which has retained the brown colour but is much larger with a thick cap and stem, enabling it to be strangely consumed in burger form.

Other wild species of Agaricus that people eat include A. campestris (the field mushroom), A. arvensis (the horse mushroom), and A. augustus (called the "prince", although I suspect the "emperor" might fit better). These are good eating, but don't go hunting for 'em unless you're an expert. And by that I mean a trained mycologist, not some dude who read a book and "hasn't got sick yet".

All species of Agaricus contain hydrazines, which are compounds that contain two bonded nitrogen atoms. Of these, which include in their ranks such luminaries as gyromitrin and monomethylhydrazine, the most abundant is an aromatic hydrazine known as agaritine.

The vast majority of hydrazines are known carcinogens. Agaritine is rapidly broken down by animal enzymes to form 4-(hydroxymethyl)phenylhydrazine (HMPH) and 4-(hydroxymethyl)benzenediazonium ions (HMBD), both of which are very unstable and have been shown to be carcinogenic. Extracts of A. bisporus have been shown to damage DNA in test tubes (Ames test) and it has been demonstrated that mice display a significant increase in the incidence of several types of tumours after they are fed uncooked mushrooms. As there is currently insufficient evidence to conclude otherwise, agaritine is presently only suspected to cause cancer in humans.

It should be noted that agaritine and its derivatives are likely degraded by heat, so cooking your mushrooms would be expected to lower the risk of developing cancer. If such a risk is real. But honestly, raw mushrooms can't compete with ones that have been sauteed in butter.

- Kondo K, Watanabe A, Akiyama H, Maitani T. The metabolisms of agaritine, a mushroom hydrazine in mice. Food Chem Toxicol. 2008 Mar;46(3):854-62. Epub 2007 Dec 3.