Abstract
About 7 % of the U. S. population reports using botanical dietary supplements. Increased
use of such supplements has led to discussions related to their authenticity and quality.
Reports of adulteration with substandard materials or pharmaceuticals are of concern
because such substitutions, whether inadvertent or deliberate, may reduce the efficacy
of specific botanicals or lead to adverse events. Methods for verifying the identity
of botanicals include macroscopic and microscopic examinations, chemical analysis,
and DNA-based methods including DNA barcoding. Macroscopic and microscopic examinations
may fail when a supplement consists of botanicals that have been processed beyond
the ability to provide morphological characterizations. Chemical analysis of specific
marker compounds encounters problems when these compounds are not distinct to a given
species or when purified reference standards are not available. Recent investigations
describing DNA barcoding analysis of botanical dietary supplements have raised concerns
about the authenticity of the supplements themselves as well as the appropriateness
of using DNA barcoding techniques with finished botanical products. We collected 112
market samples of frequently consumed botanical dietary supplements of ginkgo, soy,
valerian, yohimbe, and St. Johnʼs wort and analyzed each for specific chemical markers
(i.e., flavonol glycosides, total isoflavones, total valerenic acids, yohimbine, and
hypericins, respectively). We used traditional DNA barcoding techniques targeting
the nuclear ITS2 gene and the chloroplast gene psbA-trnH on the same samples to determine the presence of DNA of the labelled ingredient.
We compared the results obtained by both methods to assess the contribution of each
in determining the identity of the samples.
Key words
dietary supplements - HPLC - DNA barcoding - adulteration - label claims
