Date of Award
Master of Science (MS)
DNA barcoding is a technique that uses a short DNA fragment to identify a specimen to the species level. This technique is essential in situations where a lack of distinguishing morphological characteristics makes identification impossible. In the Río Grande Valley a variety of herbal supplements are cheap, readily available and sold as “Arnica” with no information to identify the contents. The appearance of dried and shredded material suggests that a variety of plant species are involved, belonging to the family Asteraceae. Arnica montana, also part of Asteraceae, is found in Europe and has anti-inflammatory properties used to externally treat bruises and contusions. Many species in Asteraceae contain secondary metabolites that may be hepatotoxic. From a health perspective, it is important that these products are identified to rule out safety concerns of toxicity of potentially mixed-up or misidentified materials. In this study a DNA barcoding reference library of Río Grande Valley Asteraceae was developed and subsequently a Bayesian phylogenetic approach was used to identify these unknown plant samples. The approach consisted of using matK and rbcL sequence data to identify the samples. The Bayesian phylogenetic tree confirmed the samples were not A. montana, but instead identified one species to be Trixis inula, and the remaining species were narrowed down to the subtribal level. Having obtained this information, additional analyses were conducted with highly variable nuclear ribosomal spacer sequences within those subtribes to further narrow down the possibilities. As a result the other samples were identified as Heterotheca subaxillaris, Grindelia spp. and Pseudogynoxys spp. A literature search revealed that species within each of the genera identified possess antioxidant, anti-inflammatory, anti-bacterial, anti-fungal and anti-parasitic properties some of which are highly similar to those of A. montana. The evidence obtained in this study suggests that these “Arnica” plants are not random replacements or misidentifications, as has been found in similar studies in other parts of the country, but are so far unrecognized members of medicinal plants widely used in the Río Grande Valley. This finding is warranting a much more detailed and molecular data driven ethnobotanical study of medicinal plant use in the RGV.
University of Texas Brownsville