An interesting paper has been published recently in the BMC Medicine journal:
"DNA barcoding detects contamination and substitution in North American herbal products"
The idea sounds complex, and it is, but the general results of this study are pretty scary, especially if you, like many Americans, use a number of very popular herbal remedies for all kinds of ailments.
The idea that herbal remedies are not as harmless as they are advertised to be, has been known in a skeptical community for a long time, but it is something that filters to a general public very slowly. That's because the supplement industry has been selling herbs as miracle cures that can treat anything and are harmless and side-effect-free, which is not true, of course.