Supply Chain Integrity Update – DNA Barcoding

Michael Lelah, PhD

Chief Research Scientist, Health Resources

December 1, 2015

In April, ONHA met with the New York Attorney General Eric Schniderman. The meeting was set up in response to the NYAG action on herbal supplements as a result of DNA barcoding studies. ONHA was the first trade association to meet with the NYAG. The discussion centered on improved supply chain transparency with both parties agreeing that more needs to be done to assure supply chain integrity.

ONHA had previously held a supply chain integrity webinar (June 24, 2015), where I discussed the manufacturer-brand relationship with emphasis on establishing the partnership, manufacturing to standards, trust but verify, and what to do when things go wrong.

More recently, I attended an analytical summit on DNA barcoding in Salt Lake City. This summit was organized November 5-6, 2015 by UNPA, the United Natural Products Association. I’d like to provide an update on DNA barcoding and what it means for manufacturers and consumers.

DNA barcoding of plants involves extracting short segments of DNA and then comparing the DNA against a library. It could be a useful technique in these establishment of the true identity of the original plant. This would help in reducing the possibility of adulteration. Could be a great tool for identifying fake products.

But what I learned at the summit was less than satisfying. In fact, as the method stands today it is essentially useless as an identification tool for multiple reasons, which I will list below. Consumers need to know that this method is not ready for prime time. However, also remember that many methods started this way, and over time (many years) as they were better understood and improved, they found their place in the repertoire of methods currently in use. So, not today but maybe in the future.

Here’s why consumers and manufacturers should not today rely on DNA barcoding as a means to ensure the identity of a plant in their product:

  • Most interesting, a lot of the work on DNA barcoding has been done on devil’s claw, an herbal used as a supplement, but is certainly not a major product. In fact most consumers have probably not heard of this plant. But the most interesting part is that two devil’s claw plants standing side by side in a field of devil’s claw, may not have the same DNA barcode. That’s why it is so interesting to scientists. But for ensuring identity? Huh?
  • More than this, plants can modify their DNA as a result of soil and climate conditions, so today’s DNA barcode may be different tomorrow. Then how can we confirm an ID?
  • Plants have many DNAs – found in the nucleotides, mitochondria, and chloroplasts. Also, plants contain foreign DNA – from bacteria, viruses and fungi. Which to use? Well, scientists focus on using the DNA from the chloroplasts because they are the most stable. That’s fine for green plants – that’s where chlorophyll is. But what about roots such as ginger and ginseng – they are brown? They have very few chloroplasts and thus the analysis will be of poor quality and will likely fail.
  • Using DNA barcoding actually opens up a whole new opportunity for adulteration! Create an herbal powder with sawdust and a sprinkle of the real herb. DNA barcoding will confirm the presence of the real herb. Great, now we have created an avenue for bad scientists to pursue!
  • Another problem – remember I said DNA barcoding involves comparing against a library? Well, this library exists, but it has not been verified. There are mistakes. Now what?
  • Moreover, the method has been shown to produce many false positive and false negative results. What this means is that the method is not fit for purpose. What this means is that the method does not meet the legal requirement of being “Scientifically Valid”. What this means is that it is not (yet) a reliable method.
  • This is just a short list of the problems that have to be resolved with this method. There are other issues that also will take time to address.

So what does this all mean for consumers and manufacturers? DNA barcoding is not yet an appropriate method for identity testing for plants as part of a supplement verification program. I’m not alone in that viewpoint.  The New Yorker stated its case in February in an article entitled  “How Not to Test a Dietary Supplement.”   Perhaps it could become a useful method one day. In the meantime, we go back to our tried and true methods – the alphabet soup of HPLC, HP-TLC and other microscopic botanical methods that have been shown to be scientifically valid and have been used with regularity for identity testing. This coupled with supply chain documentation control, and supplier audits – makes for a robust confirmation that the product you purchase is what it should be.