August 12, 2002
Volume 80, Number 32
CENEAR 80 32 p. 37
ISSN 0009-2347

Root is used worldwide as a flavor and a medicine


In sanskrit, it is called sweet stalk. The Greeks named it sweet root. And the Chinese, who may have known about it the longest, dubbed it gancao, which means sweet grass. The strong, dark candy, famous to me as the fastest way to colored saliva, was prized by entire civilizations centuries before Christ.

One thing is well established: Licorice--both the plant and the candy made from it--is sweet. Many fans suggest it is 50 times sweeter than table sugar, though some researchers have placed it at more than 150 times sweeter than sucrose.

This intense sweetness can be traced to glycyrrhizic acid, a multipurpose molecule that consists of two sugar moieties attached to a steroidlike triterpenoid. The varied properties of the molecule have led to the surprising mix of products that hold licorice today: medicines, cough syrups, herbal supplements, gum, tobacco, drinks, and, of course, candy.

Glycyrrhizic acid resides naturally in the root of the licorice plant, Glycyrrhiza glabra. A shrubby, woody-rooted plant with feathery leaves and light blue-violet flowers, it grows in the wild in many Middle Eastern, European, and western Asian countries.

The branching roots grow down as far as 3 feet and out laterally up to 20 feet. The root is harvested, dried, and sold to licorice processors. They, in turn, boil and beat the extract out and repackage it as solid dark blocks, semifluid syrups, or powders.

A curious combination of industries makes use of this licorice paste. MAFCO Worldwide, Camden, N.J., which claims to be the world's leading licorice manufacturer, sells about 80% of its product to the tobacco industry, says Guy Dietrich, MAFCO's director of industrial relations and regulatory affairs. The industry uses it for flavoring cigarettes, cigars, and chewing tobacco. Beverage makers use licorice as a foaming agent. Pharmaceutical companies use the sweetness of licorice to mask the taste of bitter drugs.


SOME LICORICE ALSO ends up on the candy aisle, though the amount in the U.S. is surprisingly low. U.S. candy makers routinely swap anise for licorice in licorice-flavored candies. Anise is in the seed that often sits by the door at Indian restaurants. It has a mild flavor similar to licorice.

Dietrich says he actually sells more licorice root extract to the European confectionery industry. Licorice is more prevalent and important, both as a flavor and as a drug in its own right, outside the U.S.

Traditional Chinese medicine extensively calls for licorice as a herbal healing agent. Europeans use it as a soothing agent in cough suppressants and to help heal ulcers. And in early Western medicine, licorice was found to relieve the symptoms of Addison's disease.

Addison's disease is caused by a deficiency of cortisol, a steroid hormone which, among other things, can regulate water retention and blood pressure. Early herbalists knew that licorice treated this disease, but it wasn't until the 1960s that hypertension researchers Christopher R. Edwards and Paul M. Stewart, then at Western General Hospital, Edinburgh, Scotland, and others began to figure out why licorice was a boon.

They suggested that glycrrhetinic acid, the steroidlike constituent of glycyrrhizic acid, inhibits an enzyme responsible for inactivating cortisol in the kidney. Eating licorice essentially extends the lifetime of cortisol in the kidney.

The Edinburgh group's research prompted a string of new studies on the enzyme, 11 -hydroxysteroid dehydrogenase type 2. Steroid chemists worldwide gradually unearthed one of the body's fundamental hormone-regulating pathways, "one of the very profound discoveries in the last 15 years in medicine," says Michael E. Baker, a professor in the medical school at the University of California, San Diego. They found that local regulation of cortisol happens primarily through activating and deactivating the molecule with a ketone/alcohol conversion on the C-11 carbon.

"It's a very elegant on-off switch to regulate the action of a hormone," says Baker, who now studies how similar alcohol/ketone switch mechanisms are used to regulate a host of other hormones as well, including androgens and estrogens. Licorice, he says, may get in the wheels of a number of those activation/deactivation pathways.

Licorice helps heal ulcers by inactivating 15-hydroxyprostaglandin dehydrogenase in the stomach lining. As with cortisol in the kidney, licorice locally extends the life of prostaglandins that protect the stomach wall. The effect on prostaglandins may also explain why licorice helps soothe a cough. The extract added to some cough drops may affect the prostaglandins that release mucous.

But getting in the cogs of bioregulation pathways isn't always beneficial. Because glycyrrhizic acid allows cortisol to stick around in the distal tubules of the kidney, cortisol binds to a protein that causes the kidney to retain sodium longer than it normally would, increasing blood pressure. Other effects of high licorice consumption include water retention, headaches, lethargy, and, in massive amounts, heart failure.

Though licorice lovers in the U.S. rarely eat enough glycyrrhizic acid to get a blood-pressure boost, European physicians are now debating whether moderate doses of natural licorice have a significant hypertensive effect.

Glycyrrhizic acid, which makes up from 4 to over 20% of the root, is not the only biologically active molecule. About 300 different polyphenols, which make up 1 to 5% of the root, are suspected antioxidants, perhaps even cancer-fighting compounds.

Despite its long history, licorice may yet surprise us. Its presence in the candy aisle, at the pharmacy, among the natural food products, and on the checkout stand attest to the complexity and rich chemistry of this sweet root.


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Copyright © 2002 American Chemical Society