Authentication of herbal supplements - how it is done right.

Some of you might remember reading about the case in which the New York State attorney general’s office accused four major retailers of selling fraudulent and potentially dangerous herbal supplements and demanded through an official cease and desist notification that they remove the products from their shelves. They had used DNA barcoding to make this claim and were heavily criticized by the industry for doing so. That was a little over a year ago and some of the criticism persisted for a long time and revolves around the question how DNA barcoding was done in this particular case. However, one question remained and that was how to properly do authentication studies utilizing DNA-based species identification. Well, I think we have a pretty good answer to that in a paper that was published just yesterday. Colleagues here at the institute did a very thorough study that looked into DNA-based authentication of plants and used HTS as a prospective way to verify listed ingredients in herbal medicines and to detect adulteration.

What I like about this study is its balanced approach and what they found out can be summarized in one sentence I took from their conclusions: Quality control of herbal supplements should utilize a synergetic approach targeting both DNA and bioactive components, especially for standardized extracts with degraded DNA. But of course their take-home message is a bit more complex which the nicely summarized in a list of suggestions that I find very helpful for everyone involved in herbal material authentication:

1. The NGS workflow developed in this study enables simultaneous detection of plant and fungal DNA. This protocol can be utilized by manufacturers for screening of potential mycotoxin-producing and pathogenic fungi, for quality assurance of raw plant materials, contamination control during the production process, and for assessing the purity of the final product.
2. Sanger sequencing should not be used for testing herbal supplements, due to its inability to resolve mixed signal from samples containing multiple species. NGS-based approaches are far more superior, enabling reliable and effective detection of DNA in complex mixtures.
3. Aside from intended or non-intended substitution, cross-contamination with non-target plant DNA may occur at any stage during growing, harvesting, manufacturing, handling or laboratory analysis of plant material. NGS-based methods would detect such traces, in addition to target DNA. By contrast, when the contaminant template is preferentially amplified, Sanger sequencing may detect only contaminant DNA, leading to biased and misleading outcomes.
4. Diversity of fungi in herbal supplements will be determined by a combination of pathogenic, endophytic and mycorrhizal fungi naturally associated with live plant material, saprophytic fungi proliferated during drying and storage, and strains involved in the fermentation during manufacturing of bioactive components. Although this entire spectrum would be easily detected by NGS methods, interpretation of test results should focus on potential mycotoxin-producing fungi and human pathogens.
5. Quality control of herbal supplements should utilize a synergetic approach targeting both bioactive components and DNA, especially for standardized extracts with potentially degraded DNA.