Herbs in drug discovery

Have you popped an aspirin lately? Thank a willow. Have you ever had your eyes dilated at the eye doctor’s? Thank deadly nightshade. Have you ever traveled somewhere tropical and taken preventive antimalarials? Thank you, cinchona. Used (or had a partner who used) hormonal contraception? That’s thanks to wild yam. Plants are potent medicines!

Willow (Salix spp.)

Yep, it’s true. These plants contain chemicals used to develop drugs with incredible actions on the human body. We all pretty much know in the backs of our minds that plants have contributed to pharmaceutical development, though the specifics of this might be fuzzy.

Let’s start by understanding the basics of how plants turn into drugs. You already know from high school biology that plants have chlorophyll and carbohydrates. They also contain lipids and proteins. These are the primary building blocks for plants to build and maintain their cells and selves.

Plants also have all sorts of chemical compounds (called secondary metabolites—secondary to those primary building blocks) that protect them from predation and pathogens and attract beneficial associations with pollinators or other creatures that help the plant.

Plants’ chemical compounds are mainly in the form of alkaloids, terpenes, terpenoids, glycosides, polyphenols, and phenolics. These chemicals are isolated, extracted, and transformed into modern-day drugs. Plant chemicals are sometimes no longer used to make drugs because the molecules can be synthesized artificially. But discovering and recognizing the plants’ chemicals helped us realize that we could get a medicinal action in the first place.

Foxglove (Digitalis purpurea)

Here are some (of the literally hundreds! of) plants used in the formation of pharmaceutical and over-the-counter drugs, either presently or historically:

Willow (Salix spp.) bark contains salicin, a phenolic glycoside that acts as an analgesic and is often used for reducing pain and fevers. Willow is aspirin-like in its use but also its contraindications, as both willow and aspirin can inhibit blood clotting, promote bleeding, and irritate the stomach.

Deadly nightshade (Atropa belladonna) produces atropine, a sedative with parasympathetic innervation effects on the iris, among many other uses. (Also, the berries of this plant likely killed Shakespeare’s Juliet. Just because plants are “natural” doesn’t mean they are safe.)

Atropa belladonna

Foxglove (Digitalis purpurea) is the source of digitoxin, digitalin, digitalis, and digoxin, all used in heart medications. How does it work, you might ask? The active compound digitalis blocks and disables the sodium-potassium ion pumps in the cell membranes of heart cells. This makes the level of sodium and calcium ions rise inside of these cells, making the heart muscle contract more strongly, providing a stronger and more regular heartbeat.

Cinchona (C. ledgeriana and other spp.) produces quinine, that oh-so-important discovery that gives tonic water its bitterness and gin-and-tonics their antimalarial activity. The common antimalarial drugs chloroquine and mefloquine are synthetic analogs of quinine.

Wild yam (Dioscorea villosa) produces diosgenin, which mimics estrogen and progesterone and can be converted into active steroid compounds in a lab.

Mormon tea (Ephedra sinensis) produces ephedrine, which is hypertensive and also useful for allergies.

Madagascar periwinkle (Catharanthus roseus) has alkaloids (vinblastine, vinorelbine, vincristine, and vindesine) used in many popular cancer-fighting and anti-tumor drugs.

Horse chestnut (Aesculus hippocastanum) is the source of aescin, used as an anti-inflammatory.

Camphor tree (Cinnamomum camphora) produces camphor, which is used as a bronchodilator (opens up airways) and rubefacient (promotes circulation on the skin).

Poppies (Papaver somniferum) produce codeine, which is an analgesic (pain relieving) and antitussive (helps calm coughs).

Bouganvillea (B. spp.) produces pinitol, an expectorant (which helps expel mucous from the lungs and sinuses).

Wild yam (Dioscorea spp.)

The list goes on and on. And more drugs are being discovered all the time. Pretty cool.  Pretty powerful.

Still, it’s important to note two things:

First, all these drugs are based on isolating individual compounds in plants. It’s easier to study them that way within dominant Western scientific frameworks. But that’s not how people traditionally used plants throughout history. They used whole plants. In whole plants, there are many compounds with potential medicinal efficacy, individually and in combination. Sometimes plants’ multiple compounds act together to do something different – that idea of the “whole being greater than the sum of its parts” – which we call synergy. We should study whole plants and synergy more – much is left to understand about therapeutic impacts and potential.

Second, sourcing these plants to produce drugs has many environmental and social ramifications and connections that we tend not to discuss enough. Like how Indigenous knowledge almost always provides the basis for these amazing medicinal plant “discoveries,” yet Indigenous people and local communities who use these plants receive no acknowledgment or associated benefits of drug development coming from their knowledge. Nor have they typically had any power in conversations over their intellectual property and the applications of their traditional practices on a global scale. This issue deserves deeper discussion and serious corrective action to foster environmental and social justice.

Madagascar periwinkle (Catharanthus roseus)

Lastly, I must give a disclaimer: Please do NOT try these plant medicines at home. Instead, do more research and talk to your doctor before ingesting any of these (and other) medicinal plants. I don’t want any readers to go the way of Juliet…

Some additional references and resources to learn more:

eCornell’s Medicinal Plants certificate program course materials 

Article: Plants as a Source of New Medicines

Article: List of Medicines Made from Plants

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