Most herbal products, available to buy as alternative medicines, may be contaminated. Reporting in BioMed Central's open access journal BMC Medicine researchers demonstrate the presence of contamination and substitution of plant species in a selection of herbal products using DNA barcoding.

There is currently no best practice for identifying plant species in herbal products. Traditionally plants are identified through the appearance of the whole plant. This method is not useful though when analyzing processed plant material. DNA barcoding analyses a short genetic sequence from the plant's genome and identifies small differences that allows species identification. In this new study the researchers used barcoding to examine the plant species found in a sample of herbal plant products.

The results showed that 59% of the products contained plant species not listed on the labels. Over two thirds of the products tested had plant species present which were a substitution for the plants listed on the label and a third of products also contained other species that may be a filler or contamination.

According to the World Health Organization, the adulteration of herbal products is a threat to consumer safety. In this current analysis the researchers detected plant species that could pose serious health risks when consumed. The results revealed plant species with known toxicity, side effects and/or negatively interact with other herbs, supplements, or medications were present in some products.

The authors concluded that the contamination and substitution dilute the effectiveness of otherwise useful remedies, lowering the perceived value of all related products because of a lack of consumer confidence in them. 'We suggest that the herbal industry should embrace molecular diagnostic tools such as DNA barcoding for authenticating herbal products through testing of raw materials used in manufacturing products. This would be a minor cost to industry with a limited amount of bulk product testing, which would certify a high quality, authentic product', said Dr. Steven Newmaster of the University of Guelph and lead author of the paper.