Botanists Explain The Chemical Roots Behind Your Favorite Bitters

Want to discover the biodiversity of bitters? Listen to a live radio conversation with botanists and read a book excerpt about the basics of bitters from Botany at the Bar.

When you take a sip of a cocktail laced with bitters, you might be sipping on a bit of botanical biodiversity. For centuries, humans have harnessed the botanical extracts to not only enhance the flavors of food and drink, but to improve therapeutic treatments and remedies. These chemical compounds in plants paint portraits of different cultures and plant varieties to Selena Ahmed, ethnobotanist at Montana State University and co-author of Botany at the Bar.

“Doing field research in different communities around the world, we’ve seen different cultures extracting plants from their local biodiversity and really seeing these extractions as a common cultural thread of cultures around the world and through time,” Ahmed said in a recent interview on Science Friday.  

The stories behind bitters are steeped in history from around the world. Ahmed and book co-authors Ashley DuVal and Rachel Meyer have traveled to places in Asia, Africa, South America, and more to understand the deep-rooted history and science of bitters—“bringing back flavors from the field,” DuVal said in the SciFri interview. 

Before the interview, you told us your favorite underappreciated root, leaf, seeds, and drinkable plant flavors on our app SciFri VoxPop, where you can answer questions and tell us stories for future interview topics. Science Friday followed up with the three botanists to hear more backstories on your favorite bitters—from the flatulence calming qualities of fennel seed to the unexpected ties between sassafras and MDMA. Read their responses below! 

The following responses by Botany at the Bar authors Selena Ahmed, Ashley Duval, and Rachel Meyer are edited for length and clarity.

The tart and fruity taste of hibiscus is truly unique. There are several hundred species of Hibiscus native to warm-temperate, subtropical, and tropical regions around the world. Dozens of these species are used in beverages, food, and medicine. 

In West Africa, the calyx (outermost whorl of a flower that covers and protects the petals as they develop) of hibiscus flowers are prepared in water in a tisane, or medicinal tincture, known as bissap. This is very similar to other regions’ preparations, including karkadé in Egypt and Sudan, gul e hhatmi in Iran, agua de jamaica in Mexico and Honduras, orhul in India, and sorrel in Jamaica. In Sudan, Hibiscus sabdariffa has been used for treating hypertension, cold and flu, and for encouraging fluid balance. In Uganda, the green hibiscus leaves are also consumed in a similar way to spinach. 

The flavor and healing properties of hibiscus are attributed to over 30 plant chemicals, or phytochemicals, including the anthocyanins that impart the rich crimson color. The color is appreciated for ritual and beauty, usually making non-alcoholic drinks more enticing. A lot of the tanginess of hibiscus comes from vitamin C and various acids including allo-hydroxycitric acid lactone, a compound unique to hibiscus. Hibiscus extracts as a whole slow the digestion of carbohydrates, which is useful for treating symptoms of type 2 diabetes. 

For making bitters and cocktails, the tart and fruity taste of hibiscus pairs well with many flavors like ancho chili, lime, rosemary, basil, ginger, mint, cherry, and apple. We also love it with other flowers including jasmine, linden, and blue pea (Clitoria ternatia, which contributes its own color). Yum! 

Fennel seed (Foeniculum vulgare) in the Apiaceae botanical family is a great example of a flavorful spice used in cocktail bitters that has digestive benefits. While fennel’s aroma and taste has hints similar to licorice, its own unique flavor is sweet, warm, and herbaceous. The taste can do wonders in food and drink by masking bitter and sour flavors. 

But the chemical properties of fennel seed do more than enhance flavor. Throughout Asia, Europe, and Africa, fennel has long been used for overall digestion—helping to relieve bloating, colic, constipation, diarrhea, flatulence, gastritis, irritable bowel syndrome, and stomach ache. The seed is a type of carminative, a botanical or therapeutic product consumed for flatulence and cramping by either preventing intestinal gas or relieve bloating and gas by soothing the gut wall. 

Growing up in Pakistan during her early childhood, Selena Ahmed would drink a tisane made of fennel seeds in water for calming belly issues and directly chewed on fennel seeds after meals to aid in digestion and as a breath freshener. Fennel is also found in many amaros, or “bitters” in Italian. The herbal liqueur is often consumed in Italy after dinner as a digestif and carminative. 

The chemical properties of fennel seed do more than enhance flavor. Throughout Asia, Europe, and Africa, fennel has long been used for overall digestion. 

In addition to fennel, a variety of carminatives are used in bitters, such as anise, ajwain, cardamom, dill, epazote, nigella, peppermint, rosemary, saffron, thyme, and wormwood to name a few. Peppermint oil, for example, has been shown to relieve bloating by relaxing the lower esophageal sphincter and reducing the pressure differential between the esophagus and stomach.   

The flavor and healing properties of carminatives is linked to a complex phytochemical profile of over a hundred different compounds. In synergy with other aromatic terpenoid (organic chemicals from terpenes), anethole is one of the primary flavor phytochemicals that gives digestive benefits to fennel seed. Anethole is not limited to fennel and other members of the Apiaceae botanical family; it is also found in species such as licorice in the Fabaceae or bean family. The volatile compound limonene is one of dozens of phytochemicals that acts with anethole for the carminative action of fennel. 

We love sassafras, too! Sassafras used to enjoy a much wider history of use as a flavoring, but in the 1960s researchers found that safrole, a major constituent of the essential oil from American sassafras root bark, was a potential liver carcinogen in rats. This resulted in the federal prohibition of safrole and sassafras extracts in perfumes and foods like candy and root beer. However, leaves do not contain a detectable amount of safrole as determined by liquid chromatography, and have been safely consumed for centuries by Choctaw Indians, who introduced it to early Cajuns as a thickening for gumbo. In fact, the Choctaw word for sassafras “kumbo” might have been the root of gumbo, although the Cajuns call the ground leaf filé powder. 

We discovered this thickening property the hard way, after boiling a tisane from the ingredients of an Eastern Forest-themed blend gunked up all of our strainers. Even after several rounds of filtering, this blend, a mixture of over a dozen different plants native to the forests of the Northeastern U.S., had the consistency of maple syrup!

In the United States, sassafras refers to the tree Sassafras albidium, but there are many more species in this genus in temperate regions around the world. In China, Sassafras tzumu has been used for thousands of years as a powerful medicine to treat rheumatism and trauma. Some trees have been tended by humans and have lived to be nearly 2,000 years old. The Chinese sassafras bark is very high in safrole oil. Even though safrole is a minor compound in common spices like black pepper, nutmeg, and anise (also in the Laurel family with sassafras), it’s actually a precursor of the drug MDMA. While illegal, it is undergoing testing for treating post-traumatic disorders. 

If you are foraging, sassafras trees are easy to identify—their leaves are polymorphic, meaning they have different shapes on the same plant. Some are simple, others look like little ghosts, and the third type looks like a child’s mitten! A scratch-and-sniff test for that wintergreen, root beer aroma will confirm that you have found the right plant. Try adding a leaf to your soup.

Lavender, rosemary, and basil are related plants in the same botanical family, the Lamiaceae or mint family. Sage, savory, marjoram, oregano, and thyme are also in the Lamiaceae. We often associate these plants with Mediterranean climates, such as California and the Mediterranean-bordering countries, but they really grow everywhere except for extreme deserts, the Arctic, and Antarctic. The species diversity is tremendous, at over 7,000 species! 

Lamiaceae have been used in medical and culinary systems around the world. For example, rosemary is one of the most common botanicals in Spanish traditional remedies and is often used for the treatment of gastritis, dermatitis, and inflammation. Archaeological evidence from China shows vessels with spirits made of rice, honey, and hawthorn fruit infused with medicinal plants including basil. 

The sensory and healing properties of the mint family is attributed to essential oils based on terpenoid phytochemistry. The aromatic terpenoids of the mint family have antioxidant, antimicrobial, and anti-inflammatory properties. For example, carnosic acid and carnosol, among several phytochemicals, are associated with the antioxidant properties of rosemary. Aromatic terpenoids of the mint family have also been used as preservatives and may be substitutes for synthetic ingredients. 

We do caution that while a large proportion of the Lamiaceae have aromas you might associate with good flavors and health benefits, these plants are quite powerful and potent, and should be used carefully and in limited quantities. Many are powerful sedatives and hallucinogens.