The Impact of Processing Steps on DNA Size and Quantity in Botanical Ingredients

Reviewed: Lu Z, Rubinsky M, Babajanian S, Zhang Y, Chang P, Swanson G. Visualization of DNA in highly processed botanical materials. Food Chem. 2018; 245:1042-1051.

Keywords: Camellia sinensis, chamomile, DNA barcoding, extraction solvent, filtration, ginger, green tea, guarana, Matricaria recutita, parsley, Paullinia cupana, Petroselinum crispum, schisandra, Schisandra chinensis, Zingiber officinale

Ever since the controversial publication on the authenticity of ingredients in botanical dietary supplements by Newmaster et al. in 2013,¹ and the subsequent investigation initiated by New York Attorney General Eric Schneiderman misusing a DNA barcoding approach,² the appropriateness of genetic methods to determine the identity of herbal ingredients has been a matter of much debate. One particular aspect of discussion is the influence of common manufacturing steps on the amount and length of DNA in the ingredient.

Using chamomile (Matricaria recutita, Asteraceae), ginger (Zingiber officinale, Zingiberaceae), guarana (Paullinia cupana, Sapindaceae), parsley (Petroselinum crispum, Apiaceae), and schisandra (Schisandra chinensis, Schisandraceae) as examples, the length and quantity of DNA was evaluated in dried whole herb, sterilized powder, and extract mixed with maltodextrin. Details of the extraction, such as the type of solvent, duration of the extraction, temperature, and further processing steps, e.g., spray-drying, were not provided. The influence of the extraction solvent was determined using chamomile flowers extracted with water, and 20%, 50%, and 80–90% aqueous ethanol mixtures, respectively. The changes in the quality and quantity of DNA after filtration was also evaluated using green tea (Camellia sinensis, Theaceae) and black tea, although the exact type of filtration was not specified by the authors.

According to the authors, the size of the DNA recovered in a majority of the sterilized powders was below 600 base pairs (bp), and varied between 20 and 220 bp in the extracts. With the exception of chamomile, DNA concentrations were found to be approximately 10 times lower in the sterilized powder compared to the whole dried herb. The DNA concentrations were generally lowest in extracts, but the decrease from powdered material to the extract varied substantially depending on the starting material.

The type of extraction solvent did not seem to have much of an impact on the presence of DNA. Even in the most lipophilic solvent tested, 80% ethanol in water, there were measurable amounts of chamomile DNA. Similarly, filtration led to a ca. 2-4-fold reduction in the amount of available DNA in the tea samples, indicating that common filtration steps used in dietary supplement manufacturing may not have a sizable impact the concentration of DNA in the extract.

Comment: The manuscript provides useful information about the impact of various processing steps on the quality and quantity of DNA in botanical materials. DNA fragmentation and loss has been reported previously, but the impact of the solvent choice and certain specific steps, e.g., grinding or filtration, has not been well characterized. While a more detailed description of the various steps along the manufacturing process would have been valuable, the data in the manuscript should be useful for those who work on genetic methods of botanical ingredient identification. It remains to be seen if the method used to visualize the DNA through ligation to adapters with a known sequence and subsequent PCR will be more widely adapted, or if the commonly used fluorescent-based detection methods will prevail.

References

1.     Newmaster SG, Grguric M, Shanmughanandhan D, Ramalingam S, Ragupathy S. DNA barcoding detects contamination and substitution. BMC Medicine 2013:11:222. doi:10.1186/1741-7015-11-222.

2.     A.G. Schneiderman Asks Major Retailers to Halt Sales of Certain Herbal Supplements as DNA Tests Fail to Detect Plant Materials Listed on Majority of Products Tested [press release]. Albany, NY: New York State Attorney General’s Office; February 3, 2015. Available at: www.ag.ny.gov/press-release/ag-schneiderman-asks-major-retailers-halt-sales-certain-herbal-supplements-dna-tests. Accessed February 13, 2018.

3.     Lo YT, Li M, Shaw PC. Identification of constituent herbs in ginseng decoctions by DNA markers. Chin Med. 2015;10(1):1.

4.     Parveen I, Gafner S, Techen N, Murch SJ, Khan IA. DNA Barcoding for the Identification of Botanicals in Herbal Medicine and Dietary Supplements: Strengths and Limitations. Planta Med. 2016;82(14):1225-1235.

5.     Harbaugh Reynaud DT, Mischler BD, Neal-Kababick J, Brown PN. The capabilities and limitations of DNA barcoding of dietary supplements. March 2015. Available at: http://www.authentechnologies.com/wp-content/uploads/2015/04/Reynaud_DNA_Barcoding_White_Paper.pdf. Accessed February 13, 2018.