DNA Barcode Authentication of Devil's Claw Herbal Dietary Supplements.

Devil's claw is the vernacular name for a genus of medicinal plants that occur in the Kalahari Desert and Namibia Steppes. The genus comprises two distinct species: and . Although the European pharmacopeia considers the species interchangeable, recent studies have demonstrated that and are chemically distinct and should not be treated as the same species. Further, the sale of as an herbal supplement is not legal in the United States. Four markers were tested for their ability to distinguish from : , , nrITS2, and . Of these, only was successful. A novel DNA mini-barcode assay that produces a 178-base amplicon in (specificity = 1.00 [95% confidence interval = 0.80-1.00]; sensitivity = 1.00 [95% confidence interval = 0.75-1.00]) was used to estimate mislabeling frequency in a sample of 23 devil's claw supplements purchased in the United States. PCR amplification failed in 13% of cases. Among the 20 fully-analyzable supplements: was not detected in 75%; 25% contained both and ; none contained only . We recommend this novel mini-barcode region as a standard method of quality control in the manufacture of devil's claw supplements.