Alliums: giving the immune system a smelly leg up

By February I am generally fed up with the cold and flu season, and this year is no exception.  Our household has been hit hard by a cold/bronchitis 1-2 punch, and we’ve been single-handedly keeping the makers of Ricola and our local Pho (Vietnamese chicken soup) shop financially solvent for the last few weeks.

It’s about this time that I start musing about zinc, antivirals, ICAM-1 inhibitors, VP4 protein based vaccines…in short, why the heck haven’t we found a way to beat the common cold?  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

Bitter but beneficial: salicylic acid and willow bark

After the last half-marathon I ran two weeks ago my longer runs have been hampered a bit by a nagging inflammation in my right lower hip muscle (piriformis strain: it’s a pain in the butt).  I was reflecting on this mild misfortune this weekend as I was reaching the home stretch of a very pretty 12-miler near the water, which went right past a clump of willows in early flower.  (Salix lasiolepsis…I think.  Salix laevigata is also native here, but the loose open buds looked more like lasiolepsis).  This provided an ample reminder of the general awesomeness of willow bark’s key pharmaceutical component, salicylic acid, and its more famous derivative, acetylsalicylic acid.

Willows by the water: a stand of flowering Salix.

Willow flowers just past the fuzzy pussy-willow stage. These look right for S. lasiolepsis; S. laevigata flowers stay more compact and fuzzy.

Good for a whole range of what ails you:

One of the more well-publicized botanical myths is that aspirin comes from willow bark.  This is only a short hop from the truth.  The actual anti-inflammatory produced metabolically by willow is salicylic acid–depending on the species and time of year, willow bark contains between 0.08 – 12.6% salicin, the metabolic precursor of salicylic acid.  Salicylic acid (historically purified in large quantities by boiling the bark of white willow, Salix alba) is readily acetylated into acetylsalicylic acid, trademarked as Aspirin.  You might have made acetylsalicylic acid back in chemistry class, or you leave aspirin tablets somewhere damp, you might notice a vinegary smell as they hydrolyze back to salicylic acid and acetic acid. Curiously, while Bayer still holds the trademark on “Aspirin”, “aspirin” is generic.  A/aspirin (hmm…not sure what the trademark rule is on capitalization at the start of a sentence) is part of the NSAID group of anti-inflammatory drugs–useful at reducing fever and throbbing pain.   Aspirin also exerts a potent anticoagulant effect by inhibiting the platelet aggregant thromboxane, so many people take it to reduce the risk of stroke or blood clots following surgery.

Salicin and salicylic acid, found in willow bark, and acetylsalicylic acid, better known as aspirin.

Salicyclic acid is also anti-inflammatory but is probably more recognized for its antibiotic effects; it’s one of the most common topical treatments for the bacteria that cause acne.  This handy dermatological property is of course just a human co-option of the plant’s own defense system: salicylic acid is produced by plants in response to stress, and reduce their vulnerability to bacterial infection.

It’s not all good news though…

The reason we don’t take salicylic acid orally as a pain killer is partly because the pharmacokinetics are a little different from aspirin, but mostly because salicylic acid is very rough on the stomach.  Acetylsalicylic acid is less irritating (for reasons I have been hard-pressed to discern–it’s a weaker acid, but at stomach acid pH that shouldn’t make a difference), but it can still cause ulcers and stomach bleeding if taken in too high an amount or with other NSAIDs.  What’s more, the conjugate base of salicylic acid, salicylate, is damaging to the hair cells of the inner ear in some people (salicylate sensitivity).  Chronic aspirin consumption can cause tinnitus when the acetylsalicylic acid hydrolyzes back to salicylic acid in the bloodstream.

Extra nitty gritty: this bitter pill to swallow has a pleasant aftertaste

So. Pretty versatile, right?  A quick hunt through the scientific literature for salicylic acid entries yields a complex mixture of rheumatology, dermatology, cardiology, botany, auditory and gustatory references.

Wait, gustatory…?  Yes.  Because as you know if you’ve ever had the misfortune of having to down an aspirin without a glass of water, salicylic acid and acetylsalicylic acid taste just awful–they’re the very definition of bitter.  This was, in fact, a significant hitch in marketing acetylsalicylic acid early in its commercial development, and pharmacologists tried out a range of less effective and even toxic variants to try to make it more palatable before resigning themselves to just mixing it into a sugary syrup or coating the pills.

Curiously, the bitterness of salicylic acid and its derivatives has become an independent asset to science, because they’re the perfect compounds to study the physiology and chemistry underlying bitter taste detection.  Salicin (basically salicylic acid with a glucose ether instead of a carboxylic acid) was recently used to study the crystal structure of the “bitterness” taste receptor hTAS2R16.

Why aspirin tastes so bad: two proposed models for the interaction of salicin (blue) with key amino acids (green) in the bitterness taste receptor hTAS2R16. From Sakurai et al., J. Biol Chem 2010.

So if you find yourself near fresh water in the next couple weeks, enjoy the budding willows, but don’t take a bite out of the bark.


Two book reviews: Edible and Useful Plants of California, and Nature’s Garden.

Last weekend I got two books about edible plants and foraging, and after having a chance to give them both a good perusal, I’m excited about each of them but for different reasons.  They’re actually nicely complementary: some of the weaknesses of one are strengths in the other.  This is a longish post, so here’s the take-home message for the impatient: I’m really glad I bought both, but if I had to recommend just one, I’d go for Nature’s Garden.

1) Edible and Useful Plants of California.  Charlotte Bringle Clarke, 1978.

The first thing worth noting about this book is that it’s older than I am, which means it’s been around for a long time and has been followed by a couple generations of foragers; in fact it’s one of the references for the second book I got.  Since all the same plants are available now as in the 70s, the publication year isn’t really an issue–it isn’t as if the content has gone out of date.

Solid field guide to local foodstuffs. Sadly, the photos on the cover are a sizable fraction of all the photos in this otherwise excellent book.


-Regional specificity and completeness: All the plants are found wild in California, and there are many, many entries.  All the wild CA plants I’ve highlighted so far (manzanita, nettle, fennel, radish, etc) are in there, and I’ve been delighted to find that quite a few plants I recognize are in there that I never knew were edible.  Field trips galore!

-Organization: She’s broken the book down into sections by type of location (mountains, coastal, urban, etc.), which will be handy for foraging.

-Recipes!  For more than half of the plants mentioned, there’s a recipe given, and sometimes there are several.  I’m already looking forward to fennel seed cookies,  fancy nettles with bacon, oxalis lemonade, and a few dozen more for plants I’ve only ever eaten raw, or have never tried.

-Preparation and harvesting tips: It’s quite clear that she approaches plants with food in mind (as if the title and recipes weren’t a giveaway).  She’s conscientious about highlighting which part of the plant is edible and how to prepare it.

-Glossary and index: there’s a very good section about nomenclature for different parts of plants.  The index is sound, with entries for common name, Latin/binomial name, and use.

-Physical size: this is a little book: about 5×7″ and less than 200 pages long.  Easy to put in a pocket (well…maybe for guys) or bring on a backpacking trip.


-Pictures.  There are a handful of photographs on the front cover and a few pages of smallish photos in the center of the book, but otherwise all the plants are represented with line drawings (or in some cases, no picture at all).  This is insufficient for gathering unfamiliar plants: you have to be absolutely sure a wild plant is what you think it is before you eat it.  Between things like iPhones and Google images, this is not a crippling limitation: once you know what name to look for it’s easy to find lots of pictures.  But you couldn’t just take this book off into the woods and be able to tell whether you have wild carrot or poison hemlock.

-Look a-likes (or lack thereof): many of the plants that are listed look similar to other, less palatable or even poisonous plants, and there’s very little attention given to what an edible plant could be mistaken for, and how to discriminate between possibilities.  There’s also little attention given to the pitfalls of particular plants: elderberry is delicious to some people, but can cause bad stomach aches in others, and should be sampled cautiously.  Cow parsnip is huge and can feed an army…unless you’re allergic to it and break out in blisters if you handle it.

-Organization: apart from breaking the plants down into regions where they grow, the entries seem pretty haphazard.  This is not such a problem because the index is good.


-Historical info.  There’s quite a lot of discussion about which Native American tribes used the plant and for what.  Because I’m mostly interested in the book as a food guide, this isn’t so much a plus for me, but it may be for others.

-Other uses: if you want plants to make into cloth or bowls or boats, you can use this book for that, too.  Uses for plants other than edibility are given in many cases.

2) Nature’s Garden: A guide to identifying, harvesting and preparing edible wild plants.  Samuel Thayer.  2010.

The cover has a fair sampling of the breadth of content: Blueberries, walnuts, prickly pears, many delicious things described with lots of pictures, careful thoroughness and a handful of funny stories.

Samuel Thayer has two books: Nature’s Garden is the sequel to Forager’s Harvest.  Based on how awesome Nature’s Garden is, I’m eager to get Forager’s Harvest as well.  (I just can’t help giving a word of caution, though: if you mix these two titles up in your head like I did and go looking for Natural Harvest, that will lead you to a very different book.  Eww.)


-Pictures!! There are many large photographs for almost all of the plants described.  In most cases he’s been careful to include pictures of several different parts of the plant, so you’ll have a clear image of the root, stem, leaf, flower, and fruit.

-Thorough harvesting tips. There are over 20 pages on acorns alone:  which species taste best, how to choose fresh acorns from old, how to spot weevil holes, several methods for how to crack them, grind them, leach them, dry them…it’s very complete.  If I wanted to get into eating acorns, I could confidently use this book to get me from tree to bread.  For all the plants in this book, he’s pretty conscientious about detailing which part to use, when it’s best to harvest, what differentiates a tasty example of the plant from a less-tasty one, and what tools to use to collect the best parts.

-Look a-likes: this is stellar.  For plants with dangerous look a-likes, he’s put in a ton of side-by-side pictures of each part of the plant, and binary guides for telling which is which.  I think anyone could confidently tell wild carrot from poison hemlock with this book.  Amazingly, I found out that something I’ve been avoiding my entire life, thinking it was deadly nightshade, is actually edible black nightshade.  Even for non-hazardous look a-likes there are helpful rules given for telling them apart: for example there’s a multi-part guide to telling apart all the edible members of the asteraceae family (dandelions, wild lettuce, chicory, salsify, etc).

-Glossary and index: like Clarke’s book, this book also has a very good guide (with pictures) to the names of plant parts, a glossary of all terms, and a good, cross-referenced index.

-Narrative style: It’s also a really fun read, with a chatty tone and plenty of anecdotes.  I literally laughed out loud at some of the foraging myths–like the wilderness traveler who patiently explained to his native guides that eating wild food was dangerous, and how they interpreted this as him being like “We can’t eat these bananas!  They are probably deadly false bananas!  Doesn’t this wilderness have any labels?”


-Limited content.  The trade-off for covering each plant in such awesome detail is that there just isn’t room to cover that many plants. I think there are about 40-50 edible plants mentioned, while I know there are actually many more than that in California alone, thanks to Clarke’s book.

-No geographical partitioning.  Samuel grew up in the Midwest, and all the plants he introduces can be found there, but only 75% can be found in CA.  Apart from giving this overall percentage of how many of these plants are found in each state, and general environmental preferences for each plant, he doesn’t usually really clarify which plants can be found where.

-No recipes.  Lots of detail on which part of the plant to pick and what kinds of food it’s good for (flour, cooked greens, seasoning…), but no real recipes.

-Physical size: it’s a bit bigger, maybe 7X9″–so it would totally fit in a backpack but not a pocket.

Whew!  Ok. That was a lot of words, but I hope you find them useful.  If anyone wants to get together for a foraging trip and try these books out I am totally game!

Relishing Radishes

Yesterday we took our dog to his favorite place, the Point Isabelle dog park, where the wild mustard and radishes are in full flower and the ground is currently soft enough to gather roots.  The radishes were so appealingly enormous that we hauled up a handful of them, and brought them home to sample. Since the bay area is liberally strewn with radishes right now, you might want to do the same!

Radish (R. sativus, foreground, large white flowers) and mustard (background, small clustered yellow flowers), growing wild at Point Isabelle. The ripe pointed silique (seed pod) of the radish is visible in the center of the picture.

Radish flowers can be purple, white, pink, or yellow. They grow singly or in small clusters, which is one way to tell yellow radish flowers from the more heavily-clustered flowers of mustard. Another difference is the siliques, which are young and thin on this radish, but still much larger than those of mustard.

Harvesting tips:

-Don’t eat the ones that have started to flower.  The roots will be tough and fibrous.  The root should snap with a nice crunch when you chop or break it.

-look for radishes with one whorl of large leaves (not a whole clump, which signifies an older plant), and take a look at the root underneath before you dig it up.  It should be smooth and white or pink–not woody and dry, although some good roots look dry on top, so peek down under soil level. We found some very nice large radishes with appealing leaves and roots growing under the protection of fennel plants, so that might be a place to start.

Radish greens that are good for eating, from a plant with a nice big healthy taproot.

-wash and scrub them extremely thoroughly when you get them home.  I even peeled them with a carrot peeler.

-break off the long tendril-y root tip.  It’s too fibrous to enjoy.

-If you plan on eating the greens (which are good if you like bitter greens; similar to beet greens), choose evenly-colored leaves, make sure you wash each leaf thoroughly, look for and remove any bad spots, and remove the stems.

The best (and biggest) of the radish greens and roots we collected.

I followed this recipe from food and wine magazine for roasted radishes and greens.  The roots were very good cooked this way–it cut the spicy isothiocyanate flavor, and gave them a nice crisp-tender texture.  The greens were good too, but a whole bowlful of bitter greens turns out to be a bit much for me.  Definitely good side-dish material.

The finished product: roasted radishes and radish greens. Very tasty!

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, 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