Supplement Contamination – DNA Barcoding Detects Contamination and Substitution

06 May 2014
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According to the World Health Organization, herbal products available to consumers in the marketplace may be contaminated or substituted with alternative plant species and fillers that are not listed on the product labels. According to a recent publication in the British Medical Journal, the adulteration of herbal products is commonplace and could be problematic for consumer health.

A Canadian team, headed up by Steven Newmaster at the University of Guelph in Ontario used a sequencing technique called DNA barcoding to investigate product integrity and authenticity of 44 herbal supplements from 12 companies. These samples were compared to leaf samples of a known provenance.

DNA barcoding
DNA barcodes were extracted by Newmaster’s team using Touchdown PCR and Big Dye (version 3.1) sequencing reactions. The resulting amplicons were then bidirectionally sequenced using standard sequencing equipment (Life Technologies). The chromatographic traces were aligned and codons read in the Codoncode Aligner ver. 3.0 (CodonCode, Dedham, MA, USA).
 
The research recovered DNA barcodes from most herbal products (91%) and all leaf samples (100%). Greater than 50% of the products tested contained DNA barcodes from plant species not listed on the labels. In 32% of the samples, unlisted plant species were detected or the main plant had been replaced with something else. For instance, rice and soy were found in 21% of the products, alfalfa was found in 16% of the products and wheat was detected in one product. Failure to list these fillers on product labels could spell trouble for consumers with an intolerance or allergy to those ingredients.

The authors of the study suggest that the herbal industry should use DNA barcoding as a cheap and effective way of testing raw materials to protect consumer health and improve product labeling.
Graham Lord, director of the UK's National Institute for Health Research Comprehensive Biomedical Research Centre, also recently published a study showing that millions of people may be exposed to a risk of kidney failure and bladder cancer by taking herbal medicines widely available in Asia.

Supplement regulation
The introduction of recent legislation now ensures that herbal products in the UK are regulated by the government's Medicines and Healthcare Products Regulatory Agency in order to ensure they are of pharmaceutical quality, says Dick Middleton, chairman of the British Herbal Medicine Association, a group that promotes herbal medicine. "It's therefore extremely unlikely that the problems experienced in North America, where herbal products are not regulated in the same way, could occur in the UK," he says.

Without access to the correct labeling information on products, consumers are left confused about supplementation and whether plant-derived supplements provide the health benefits they promote. The same barcoding technology has also been used to help the FDA in an ongoing effort to spot fake fish products. It may be just a matter of time before DNA barcoding is used routinely on all products made from living materials, including herbal supplements, to help make products safer and of higher quality.

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Michelle Maxwell
Drug Discovery Editor