Eating periodically: is there thallium in your wasabi?

Wasabi, Iwasaki Kanen 1828
via Wikimedia Commons 

Could your wasabi peas be poisoning you?  Short answer. Maybe.

Delish recently posted an article on thallium — a highly toxic metal — in kale, the quintessential healthy green.  The Internet relished the irony of finding toxic metals in the highly touted greens. The piece points to an article in Craftsmanship magazine, which attempts to make a link between consumption of kale and thallium levels.  This is not new news.  There are dozens of reports, going back two decades, in the scientific literature of thallium in cruciferous vegetables, such as kale and brussell sprouts — and wasabi.

Thallium is definitely a nasty element, and has an infamous history of use as a poison in fact and fiction, starting with Ngaio Marsh's Final Curtain.  Read Deborah Blum's hair-raisingly fascinating Poisoner's Handbook (or her short article at Wired about a recent murder case in Princeton).  But as with everything, dose makes the poison, and the amounts of thallium in plants vary widely depending on the concentrations in the soil.  In highly contaminated soils, plants can contain enough thallium to be hazardous.  But if such highly contaminated soils were widespread, we'd have seen the effects already. (See this paper for some background.) (Also, you can leverage this ability and use it to clear out the thallium from a contaminated area.)

So how does thallium get into the plants? There is some evidence that thallium ions travel the same pathways as potassium ions (which play key roles in plant metabolism), and so might find their way into plants (and animals) though similar processes.

Thallium is also in the same column as boron, and elements in the same column of the periodic table often have similar behaviors, because their electrons are arranged in similar patterns.  For example, strontium, which is underneath calcium, sneaks into the body by way of the same processes calcium does. Boron is found in plants (coffee is a good source, and plants in the same family as kale are also heavy absorbers of boron); it is believed to be critical to cell wall formation.

And if there is boron and thallium, indium - in the same column is another likely companion. And yes, indium has been detected in plants in the cabbage family.  

As always, eating a wide variety of things is good advice, and it's key to remember that "natural" is not the same as "safe."

St. Ignatius' Beans: Strychnine and herbal remedies

Before chemists became adept at synthesizing and purifying single molecules, materia medica relied heavily on plant based materials.  The chemicals in plants are not uniformly innocuous, or safe at any dose, a point I tried to make in this article at Slate a couple of weeks ago.  A case in point:  St. Ignatius' beans.

Last fall, I was digging through a 1903 organic chemistry text (looking for examples of eponyms for this article), when a familiar name caught my eye. What was St. Ignatius doing in a chemistry textbook, an organic one at that?  Jesuits, I could understand (quinine is extracted from cinchona, also called Jesuits' bark), but Ignatius (the founder of the Jesuits) himself?

"Strychnine, C₂₁H₂₂O₂N₂, is found in St. Ignatius' bean..."  What is a violent poison doing in a bean named for Ignatius?  Despite the fact that I was up against an impending writing deadline and had a couple of dozen exams to grade, I had to know.

Faba Sancti Ignatii were first described by an Austrian Jesuit living in the Philippines in the 17th century, George Kamel, S.J. (his description was published in the Philosophical Transactions in 1699 - and yes, I looked up the Latin version).  Later authors speculated the plant was named for Ignatius because of its many medicinal virtues (which they do not list).  At the turn of the last century strychnine was part of the US Pharmacopoeia, prescribed as a stimulant — it was implicated in a early Olympic doping scandal — and for gastric upset; in the Phillipines it was often (more sensibly) the bean was worn on a string around the neck for protection against various diseases. These days it forms the basis for a homeopathic nostrum prescribed for grief and melancholia, particularly when associated with an abundance of tears.

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A version of this post appeared at Quantum Theology.

Calm amino acids

It's the time of the year when I covet both energy and calm. A young friend sent me the link to these mints, which promise both in a single package. The secret ingredient is L-theanine (structure shown at left), a naturally occurring amino acid found in Camelia sinensis. Interestingly, the dried, fermented leaves of Camelia sinensis are what I use to brew my preferred pharmacological concoction to decrease stress and increase alertness: tea.

Some amino acids (roughly 20) are used by biological systems to build proteins (the working machinery of cells). The basic structural motif of any amino acid has a carboxylic acid group (COOH, which occurs in molecules like acetic acid, aka vinegar) along with an amine group (NH₂ — certain amines are responsible for the characteristic odor of fish) as shown here:


Theanine is not one of the twenty plus amino acids used to construct proteins. There is some evidence that it works synergistically with caffeine to enhance cognitve performance, while moderating some of caffeine's less desirable effects.

So…do the mints work as advertised? I've no idea, but browsing the literature suggests that my students might reap some benefit from the multiple cups of tea I drink while grading their exams. A calm, but alert grader can't be all bad!

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Related posts:

Where does the name amine, and hence amino acid come from?
How old are whales and what does this have to do with right and left handed amino acids

A rose by any other name is poison ivy

In 1865 John Maisch published a short paper "On the Active Principle of Rhus Toxicodendron". For the unsensitized, rhus toxicodendron is the botanical name for poison ivy. Maisch isolated a fraction he considered to be the "active principle" responsible for the misery that is poison ivy and dubbed it toxicodendric acid. Are you itchy yet? (I am and Maisch surely was, he and various visitors to his lab suffered with outbreaks of poison ivy.)

By 1897 Franz Pfaff of Harvard had weighed in. Toxicodendric acid extracted from poison ivy turned out to be acetic acid - yes, vinegar, by another name, CH₃COOH. He showed the itch was in the oil.