DNA Barcode Testing of Herbal Supplements Questioned

Validity of DNA barcode testing of supplements that contain herbal extracts is being questioned following the New York Attorney General Eric Schneiderman’s order that four retailers in the state discontinue selling their store-brand products, including echinacea, ginseng, garlic, ginkgo, saw palmetto, St. John’s wort, and valerian. DNA barcoding showed that only 21 percent of the store-brand supplements contain the plants listed on the labels and that many products do not contain any DNA from a botanical source.

The attorney general also issued subpoenas requiring that the companies provide support for the health claims printed on the labels of these supplements. The supplements have now been removed from the retailers’ shelves in New York.

Nandukumara Sarma, PhD, director of dietary supplements at U.S. Pharmacopeia (USP), says that DNA barcoding is not the best test for supplements that contain extracts. USP is a scientific, nonprofit organization that sets standards for the identity, strength, quality, and purity of medicines, food ingredients, and supplements.

“Use of solvents and/or heat during extraction process can degrade—and sometimes destroy—DNA in extracts material. … The presence or absence of DNA in an extract should not be used to confirm the identity of an ingredient in the form of a plant extract,” Dr. Sarma says in a statement. DNA barcoding is a valid and useful technology, but “it is envisioned as a method to be applied mostly to non-extracted plant materials and as a complement to other chemical tests.”

Daniel Fabricant, PhD, CEO of the Natural Products Association, says that chemical analysis or chromatography should be used instead of DNA barcoding. “Once you get an extract, there essentially won’t be any DNA left. All of the products were extracts so we wouldn’t expect there to be any DNA,” he says. Use of DNA barcoding for testing supplements containing herbal extracts is “like using a screwdriver to hammer a nail and then saying the lumber was bad. It’s over-reaching and nonsensical.”

The American Botanical Society (ABS) concurs. “Microscopy and validated chemical test methods, like those found in official pharmacopeias for these seven herbs, should have been conducted to confirm the DNA findings. … We respectfully must question whether an appropriate level of scientific rigor has been applied in this case.”

The ABS has initiated the Botanical Adulterants Program to educate the herbal and dietary supplement industry about ingredient and product adulteration. It is partnering with American Herbal Pharmacopoeia and the University of Mississippi’s National Center for Natural Products Research. The program is focusing on both accidental adulteration of botanical ingredients that can occur due to poor quality-control procedures, and also on intentional adulteration. It hopes to serve as a self-regulation resource so that industry can address these problems through education rather than federal regulation. The program also intends to provide comment and guidance on the strength and/or weakness of different analytical methods used in the industry.

Holliman is a veteran journalist with extensive experience covering a variety of industries. Reach her at [email protected].