The use of DNA barcode techniques to identify the constituents of herbal dietary supplements

Abstract

Dried fragmentary plant materials, such as those often found in herbal dietary supplements, are difficult to identify to species using morphological characteristics alone. Although often partially degraded, plant DNA can survive many common types of processing (e.g. drying, grinding). Short portions (less than 200 bp) of plant DNA from herbal supplements can usually be PCR amplified and Sanger sequenced. When compared to the growing database of publicly available DNA barcode sequences, these sequences can be used to provide reliable species-level identification. For example, black cohosh (Actaea racemosa) herbal dietary supplements are commonly consumed to treat menopausal symptoms. Accidental misidentification and/or deliberate adulteration results in harvesting other, related, species that are then marketed as black cohosh. Some of these species are known to be toxic to humans. Two nucleotides in the plant barcode region consistently distinguish black cohosh from related species. Of 36 dietary supplements sequenced, 27 (75%) have a sequence that exactly matches black cohosh. The remaining 9 samples (25%) have a sequence identical to that of three Asian Actaea species (A. cimicifuga, A. dahurica, and A. simplex).