Toxic and toothsome: a tale of two wild Asteraceae

Toxic Interloper:

Not long ago, I planted a bunch of coriander/cilantro seeds in my back yard.  When the seedlings emerged, I found not only cilantro, but also this:

Not cilantro as it should have been, but common groundsel. Don’t try to fool me with your toothed leaves–I can totally see you’re sending up flower buds already.

Senecio vulgaris, known as common groundsel to me, but also as Old-man-of-the-spring. It’s just about everywhere right now–I’m seeing it along roadsides, in gardens, at the park and clawing its way through sidewalk tiles.  It starts off with lobed leaves and an emerging crown of flower buds that’s visible really early, and ends up with nearly-closed yellow flowers, and fuzzy gray seed heads like tiny dandelions (whence the “Old man” name–it looks a bit like a tousled gray head of hair). Continue reading

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Of wild carrots and the death of Socrates

There is a plant I keep encountering, both on foraging trips and while out running, and for a long time I had been entertaining the hope that it was wild carrot (Daucus carota), while secretly suspecting that it was actually poison hemlock (Conium maculatum).  These two members of the Apiaceae/Umbelliferae family look very similar as young plants (and both are sometimes called Queen Anne’s lace), but armed with Samuel Thayer’s “Nature’s Garden” on our recent Redwood Park foraging trip, I was able to pin down once and for all that…dammit, yes: it’s hemlock.

Poison hemlock, Conium maculatum. Not the wild carrot I was hoping for. Photo courtesy of Jen at willblogforfood.

The Apiaceae are a fickle lot of plants: some are friendly foodstuffs (carrot, fennel, celery, parsley, caraway), some are vicious poisons (poison hemlock, water hemlock, fool’s parsley), and some are something in between (like cow parsnip, which is edible but whose sap can be a strong irritant).  Several of them look similar as young plants, too, with rosettes of feathery leaves and umbels of delicate white flowers.

Caraway, Carum carvi. If I hadn’t read the title, I might have thought it was fennel, because all these darn Apiaceae look similar. From Koehler’s Medizinal Pflanzen.

Over the centuries, many people have been poisoned by mixing them up.  A handful of case studies from the last decade of folks who ate a variety of toxic Apiaceae can be found  here, here, here, and here.  For those who forage, wild wood survival offers a sturdy guide to telling tasty wild carrot from its toxic doppleganger.  (Quick and dirty version: hemlock has smooth stems, sometimes speckled purple or with a chalky residue.  It doesn’t smell very good, and its flowers are loosely packed in umbels, like caraway, above.  Wild carrot has fuzzy stems, smells strongly of carrot, and has tightly-packed umbels of flowers with one dark purple flower in the middle.  And if you’re in doubt, don’t eat it!)

Wild carrot, Daucus carota. Similar enough to C. maculatum to give you pause, and make you wish you’d brought some store-bought carrot leaves along for comparison. Photo from Gunther Blaich’s website.

And then, of course, there are the more sinister, deliberate poisonings. Continue reading

These pink elephants are caused by what part of the absinthe, exactly?

Back in 2002 I went to Prague, where I was able to legally sample that storied vice of brooding 19th-century artists, absinthe.  The preferred method of preparation was to pour some of the liquor into a large spoon, add a pinch of sugar, and heat it over a candle flame until the sugar dissolved.  It was a ritual that added to the sense of participating in a dangerous, clandestine tradition, and coupled with the pre-Industrial-era architecture and cobblestone streets, I would leave the pub fully expecting to run into a Van Gogh-like figure, or at least hallucinate one.

"The absinthe drinker" being visited by the green fairy. By Czech painter Viktor Oliva, 1901.

Somewhat disappointingly, I never hallucinated any depressive one-eared artists.  Or anything else for that matter.  In fact, despite the 120-proof alcohol content, I only got modestly tipsy, thanks to the absinthe’s bitter, anise-y flavor (the origin for the word “absinthe” is likely the Greek apsinthion, which means “undrinkable”).  The one time I followed the absinthe up with a couple glasses of red wine, I did end up with a headache that might have inspired some gruesomely morbid poetry, but I wasn’t feeling moved by a creative impulse so much as by the impulse to find out what had happened to my Advil over the course of 3 flights and two layovers.

Fast forward to this past St. Patrick’s Day, when my friends brought over a bottle of appropriately green absinthe made and sold just a few miles away at our local distillery, St. George’s.  While the mystique was not so pronounced in my living room as it had been in a Czech pub, the product was definitely the same: the bottle confidently proclaimed that it contained extracts from wormwood (Artemisia absinthium, the plant that gives absinthe its distinctive flavor and color).  Ten years ago, I had to go to Europe for this stuff.  Why is it legal here now? Continue reading

How to Build a Giant.

After last week’s perusal of 4-winged dinosaurs, my labmates and I got into a bit of a competition to find the most outlandish prehistoric animal, which led us to meter-long millipedes, 2-foot mayflies, and something called Hallucigenia.  What most captured our attention was that arthropods in the Carboniferous period were terrifyingly enormous.  50lb scorpions? GAAAAHH!!

Pulmonoscorpius was 70cm long, and makes me feel a tad bit better about sharing the world with the puny little several-inch scorpions we get now. Artist's rendition by Nobu Tamura, via Wikipedia.

But then we realized the Carboniferous (about 350-300 million years ago) was the same period that gave us 50-foot horsetails and house-sized ferns, and we paused long enough to ask ourselves: “Wait, hang on.  Why was EVERYTHING so darned big back then?” Continue reading

Steel magnolias: using magnolol to combat arthritis

The gorgeous display of magnolia flowers around campus has been capturing my attention over the last few weeks, but it turns out they’re just as noteworthy for their therapeutic potential as for their aesthetics. A new article in press for PLoS One (open access for everyone!) describes a novel activity for the Magnolia officinalis derivative magnolol in repressing inflammation, which is a pretty tantalizing topic for a runner like me who’s always a little bit neurotic about the health of her joints.

Flowers of Magnolia x soulangiana, a cross between M. lilliflora and M. deundata.

Continue reading

Why “Natural” isn’t always better: almond extract and cyanide

Right now the various species of Prunus are in flower all over northern California; the ornamental plums that are so popular as sidewalk decor are shedding petals everywhere, apricot blossoms are peeking out from yards, and the almond trees that crop up as renegades from the big orchards near Davis and in the central valley are covered in popcorn-y pinkish white flowers.  With constant reminders of stone fruit everywhere but none actually in season to eat, I’ve been doing a lot of baking with almonds and almond extract.

A sprinkling of wild plum blossoms (Prunus americana) on my way to lab.

Continue reading

Prettiest Plant in the Lab: Foxgloves, Digoxin, and Digoxigenin

A while ago I posted about oleander and the structural similarities between the oleander cardiac glycoside oleandrin and the foxglove cardiac glycoside digoxin.   But foxgloves express enough biologically useful (and harmful) molecules that they’re worth showcasing.  Plus they’re such nice eye-candy!

Gloves that pack a punch

The various members of the Digitalis genus, which include the gardener’s favorite foxglove Digitalis purpurea and a range of other Digitalis species, are favored ornamental plants for their tall showy flower spikes and bright colors.  A disputed but appealing origin for the name was advanced by William Henry Fox Talbot, who proposed that the whimsical ye Olde English people imagined fairies wearing the deep cone-shaped flowers for gloves, and called them folks’ gloves.  Very cute.  But given that fairies were famous not only for being adorable but also for other light-hearted mischiefs like stealing babies and poisoning livestock, it’s perhaps fitting that their pleasing-to-look-at gloves come barbed with a heavy dose of serious poison.

Enough folk's gloves for a children's book full of fairies. Digitalis purpurea, by Ferdinand Bauer.

Foxgloves are poisonous because they contain two cardiac glycosides, digoxin and digitoxin, which are found in all parts of the foxglove plant but are most concentrated in the leaves.  There are a few ways to poison yourself with foxgloves by mistake: the flowers have some appealing similarities to honeysuckle, which might lead the unwary to try to suck nectar from them.  Because the plant is still poisonous when dry, a hapless gardener might inadvertently inhale foxglove plant matter when digging or replanting near an old foxglove bed.  The leaves of foxglove (especially before it flowers) resemble and have sometimes been mistaken for comfrey, which is benign and a common basis for tea (here’s an article about several people poisoned this way).  Never fear though, ehow has a handy how-to on distinguishing comfrey from foxglove leaves; the clearest difference might be that foxglove leaves are finely toothed while comfrey’s are smooth.

Leaf of comfrey, Symphytum sps. Good for tea, beloved by herbalists, and pretty easy to confuse with foxglove leaves, pictured in the illustration above. Photo courtesy of Heather at ahandmadelife.blogspot.com, which is also a pretty nifty blog.

Finally, one of the side effects of digitalis poisoning is strong hallucinations, so there may be a handful of people out there ingesting it deliberately…but I doubt the visuals are worth the heart arrhythmias, severe nausea, fainting, coma and possible death that come with them.

Extra nitty-gritty: Digoxin as heart medicine

Cardiac glycosides like digoxin and oleandrin work as sodium-potassium ATPase inhibitors, which means that they interfere with the balance of ions inside cells. The muscle cells of the heart are particularly vulnerable to changes in sodium concentration, because sodium concentration is coupled to calcium export, and the calcium concentration inside the muscle cell is what regulates how strongly or quickly the muscle cell can contract.  When there’s too much sodium, the cell can’t efficiently export calcium, and the cell contracts too strongly as a result.  Erratic muscle contractions are certainly bad news for a healthy heart.

Digoxin: sometimes a help and sometimes a hindrance to heart function.

Unlike oleandrin however, digoxin has considerable utility as a medicine: the same calcium ion hoarding effect that’s so dangerous in a healthy person can be used to combat heart failure by promoting stronger contractions in a damaged heart, and digoxin gained FDA approval as a treatment for chronic heart failure and some kinds of heart arrythmias in 1998.

The initial use of digoxin came before beta-blockers were used to manage heart failure (HF), and there is ongoing study as to whether digoxin remains valuable as an HF management strategy in concert with other therapies. A recent article in the International Journal of Cardiology has undertaken a multivariable regression approach to attempt to classify which categories of patients are more likely to suffer higher mortality or further hospitalizations for heart failure following digoxin use.  Their meta-study combined cases of over 7000 patients, and found that higher mortality and hospitalizations for heart failure were correlated with groups of patients that were female and had high blood pressure.  Studies like this one may help identify which groups of patients can still benefit from digoxin and which groups should avoid it.

Extra nitty-gritty II: Digoxigenin as molecular label

Apart from its cardiac glycosides, Digitalis also harbors a supremely handy steroid, Digoxigenin (DIG), which I use routinely to label RNA molecules.  Digoxigenin is a fairly small little molecule that can be coupled to the nucleotides that make up DNA or RNA (nucleotides=letters: A,G,T/U, and C), and there are specific antibodies for DIG that can be used to detect it anywhere it’s bound in a cell.

DIG-UTP. This labeled "U" is incorporated into RNA molecules just like regular UTP.

So when I want to find which cells in my tissue sample are making a certain RNA, I can make a probe with a complementary sequence and some of the U’s labeled with DIG.  Then I can use anti-DIG antibodies (conjugated to an enzyme that makes a purple color under the right conditions) to look for the probe, with a technique called in situ hybridization.

A little how-to for using DIG-labeled UTP to find a target RNA by in situ hybridization.

Want more details?  Here are references for the articles mentioned:

Ather S, Peterson LE, Divakaran VG, Deswal A, Ramasubbu K, Giorgberidze I, Blaustein A, Wehrens XH, Mann DL, & Bozkurt B (2011). Digoxin treatment in heart failure – unveiling risk by cluster analysis of DIG data. International journal of cardiology, 150 (3), 264-9 PMID: 20471706
Lin, C., Yang, C., Phua, D., Deng, J., & Lu, L. (2010). An Outbreak of Foxglove Leaf Poisoning Journal of the Chinese Medical Association, 73 (2), 97-100 DOI: 10.1016/S1726-4901(10)70009-5