Sleight of Herb: Black cohosh mislabeled in medicinal products

A sizable fraction of the herbal supplements marketed as preparations of black cohosh contain none of that North American plant, researchers report. Some past studies suggested that black cohosh lessens menopausal symptoms, but 3 of 11 recently tested products instead contained related Asian species not known to have this effect.

Hundreds of thousands of women use black cohosh to combat hot flashes, estimates chemist Steven Dentali of the American Herbal Products Association, a trade group. A harvest of nearly 160 tons of the plant, mostly from the Appalachian wilderness, was reported in 2003. Root extracts go into capsules and tablets.

In the United States, herbal supplements are less strictly regulated than drugs are. Past research has turned up various herbal products that have been adulterated or lacked the natural product that they advertised on their labels (SN: 6/7/03, p. 359: Herbal Lottery).

The “new twist” is that cheap, imported raw materials have become secret substitutes for black cohosh, which is in increasingly short supply, says Fredi Kronenberg of Columbia University, an investigator in the new study.

To probe the chemical variability among black cohosh supplements, Kronenberg, natural-products chemist Edward J. Kennelly of the City University of New York, and their colleagues purchased 11 commercially available brands of the product. They then used two methods to study the molecular mixtures in the supplements and determine which plants had been used as raw materials.

They found that four of the products contained Chinese herbs known collectively as sheng ma, which have molecular profiles similar to that of black cohosh. Only one of those products also contained some black cohosh, they report in the May 3 Journal of Agricultural and Food Chemistry.

“A surprising number of products that are sold as black cohosh in the U.S., at least when we got them between 2002 and 2004, do not contain black cohosh,” says Kennelly. “These were clearly misbranded” and therefore in violation of federal labeling regulations, he says. Kennelly’s team didn’t identify the brands that lacked black cohosh.

Substitution of one herb for another—by either unscrupulous manufacturers or their botanical suppliers—is a consequence of rising demand for black cohosh, adds Bill J. Gurley of the University of Arkansas for Medical Sciences in Little Rock.

Dentali says that supplement makers should employ methods similar to those used in the study to make sure that they’ve purchased the right ingredients.

“The methods that some members of the industry are using are not rigorous enough,” Kennelly says.