Category Archives: Pharmacognosy

Wild Carrot

This time of year the highways and byways of much of the United States is abloom with wild carrot, also known commonly as bird nest, Bishop’s lace or most commonly as a naturalized form here in the United States, Queen Anne’s Lace.

It grows as an erect biennial in full sun frequently growing up to a meter or more tall. The flower head starts out as a bunched up clump of flowerlets with a tulip like shape. As the flower matures it opens up to form a saucer like shape of many small white flowers.

wild carrot

wild carrot

Its formal name is Daucus carota and is a member of the Apiaceae family (also called Umbelliferae family) which includes several other domesticated plants such as celery, parsnips, and parsley. The root of the wild carrot can be eaten when young but as it gets older it becomes to woody.

All members of this family can cause phytophotodermatitis. In a sensitive individual, contact with the leaves of the plant can cause redness, irritation and even blisters, but only after exposure to the sun. Apparently the oleoresins (plant oils) are absorbed into the skin. There a chemical reaction occurs with proteins. When the modified protein is exposed to the sun, it causes a classic dermatitis reaction not unlike exposure to poison ivy. Other plants that cause this type of skin irritation include Celery and unrelated citrus fruits.

It is not uncommon for agricultural workers handling a lot of produce to be effected. Grocers, chefs and even bartenders can be affected. An evening of mixing up bloody marys and shots of tequila followed by a day in the sun can result in irritated skin due to contact with celery and limes.

poison ivy

Poison Ivy

The old adage “leaves of three, let it be” helps to identify and therefore avoid poison ivy. The plant is polymorphic, growing as ground cover, small shrubs up to two or three feet high, or a climbing vine. It is often confused with virginia creeper which has five leaves. Formally named Toxicodendron radicans, it and other related plants contain urushiol (oo-rush-ee-ol) . The substance is present in all parts of the plant; leaves, stems, roots, and berries. Poison ivy, poison oak, and poison sumac are known to cause the characteristic itchy, blistering rash.



Other plants such as cashews also have urushiol when raw and must be properly processed, shelled and roasted, to remove the plant oil. Lacquer, the stuff that produces the beautiful shiny finish in furniture, contains small amounts of urushiol and can affect hypersensitive individuals. The name urushiol comes from the Japanese name for Lacquer, urushi.

The first time, or first few times one is exposed there usually isn’t a reaction. Only after being exposed does one become sensitized and on second exposure develop the itchy rash. This is because urushiol is an allergen, something which causes an allergic reaction , and and the allergy has to be “learned” by exposure.

Actually it is a bit more complex. Only proteins, very large molecules, can cause an allergic reaction. Much of our bodies are protein so our immune system must be able to distinguish our proteins and foreign proteins. Antibodies develop as a method to rid the body of foreign protein. A whole cascade of chemical reactions occur once the immune system identifies a foreign protein. Urushiol is not a protein but a substance know as a hapten. Haptens are small molecules which can chemically react with protein. Once a protein, for example the keratin of our skin, has reacted reacted with urushiol our bodies no longer recognize the protein as “self” but rather as foreign.

Urushiol is a fat soluble oleoresin, which means that it can penetrate the skin within an hour or two. There it reacts, “labels” the protein, and sets the allergic reaction in motion, the rash occurring several hours after exposure. Heavier exposures result in a faster reaction.

This has lead to the misconception that the allergen may be carried through the blood. For example heavy exposure to the back of the hand and only slight exposure to the upper arm means that the rash will show up on the hand first and arm only later.

Another misconception is that the fluid present in the blisters contains the poison. Once the blisters form, the poison is long gone. You can’t get a reaction just by coming in contact with someone else’s rash. You can be exposed by secondary contact however. There is a fairly wide variation is sensitivity so exposure and subsequent reaction can occur when a sensitive person handles the clothes of a less sensitive person.

In extreme cases, people are exposed by inhaling smoke particulates from burning poison ivy. This can be dangerous as the rash occurs in the throat and even in the lungs.

On Potatos and Poisons

What do foods such as potatoes and tomatoes have in common with cigarettes, pretty (Italian) women and various toxic drugs? They are all members of or derived from the same family of plants called Solanaceae. [sole-ah -nay-see-ee]

These plants are found around the world. The new world contributed edible potatoes, tomatoes, and chili peppers whereas eggplants are from the old world, specifically India. It is hard to imagine what Italians put on their pasta or what fed the Irish before the Colombian Exchange, a term used to denote the world wide trade in goods which developed after the globe was united in trade following Columbus’ discovery of the new world.

Solanaceae contributes in addition to valuable foodstuffs, numerous toxic plants including what is arguably the most toxic plant on earth- tobacco. The active ingredient is nicotine which is both additive and toxic. Fifteen percent of the world’s population and close to a third of all adults use tobacco. The World Health Organization calls tobacco addiction the leading preventable cause of death worldwide, killing over five million people a year.

One of the more interesting members of Solanaceae is Atropa Belladonna, also called Deadly Nightshade. The genus name Atropa comes from the name of one of the three fates of Greek mythology. Atropos would end the existence of mortals by “cutting the thread of life”, an obvious reference to the lethality of the plant. These and other members of Solanaceae contain Tropane alkaloids which interfere with nervous transmission. This property has been taken advantage of as both an agent of murder and as useful medicinal agents.

An integral part of an Ophthalmic exam (eye exam) involves putting drops of an Atropine solution in the eye. Today derivatives of Atropine with a much shorter duration of action are used, but I digress. Here’s where the Belladonna part comes in. Bella donna means beautiful woman in Italian. As early as the middle ages, women would use a tincture (dilute alcohol solution) of the plant to dilate their pupils, thus producing a more beautiful appearance.

Studies have shown that photographs of women retouched to enlarge the pupils are viewed as more attractive than photographs of women with smaller pupils. Not surprisingly, The rather racy slang “bedroom eyes” has the same origin. The opposite seems true. “Beady eyes” or small pupils is a pejorative term.

And while I’m on pupil size, I should mention that human infants have very large pupils. It is said that this is due to the underdeveloped musculature necessary to constrict the pupils. But is it underdeveloped eye muscles or an evolutionary adaption of the infant to be viewed as more attractive?

An eye can threaten like a loaded and levelled gun, or it can insult like hissing or kicking; or, in its altered mood, by beams of kindness, it can make the heart dance for joy.

– Ralph Waldo Emerson

From bedroom eyes to boiled potatoes and eye exams to eggplant parmigiana , its about Solanaceae.

Originally published in the Russellville Courier, January 1, 2012