The Influence of Boiling Time on
the Quality of DNA in Ginseng Decoctions
Reviewed: Lo Y-T, Li
M, Shaw P-C. Identification of constituent herbs in ginseng decoctions by DNA
markers. Chin Med. 2015;10(1):1. doi:
10.1186/s13020-015-0029-x.
In this paper, the usefulness of DNA
barcoding for authentication of plant materials used in decoctions is discussed.
In the experiment, 10 g of powdered Asian ginseng (Panax
ginseng, Araliaceae) was boiled in 200 mL for 30, 60, and 120 min.
In addition, two multi-herb decoctions were prepared consisting of (a) Asian
ginseng and aconite (Aconitum carmichaelii,
Ranunculaceae) and (b) a combination of Asian ginseng with bai-zhu atractylodes
(Atractylodes macrocephala, Asteraceae),
Chinese licorice (Glycyrrhiza uralensis, Fabaceae),
and ginger (Zingiber officinale, Zingiberaceae). For
Asian ginseng, the 26S-18S intergenic spacer region was chosen for
amplification, and primers were designed for the amplification of five DNA
fragments of different sizes (88, 121, 191, 249, and 311 base pairs [bp]). The
total amount of DNA increased with longer boiling time, indicating that more
DNA is released into the aqueous solution over time. All five DNA fragments
were able to be detected after 30 and 60 min of boiling; however, only short
polymerase chain reaction (PCR) products with sizes ranging from 88-121 bp were
amplified for samples boiled for 120 min. All components of the multi-herb
formulas could still be identified after boiling for 60 min (formula a) or 180
min (formula b) using short PCR products. As a side note, China was the first
country to recognize molecular methods as a legal basis for authentication of
crude herbal drugs, according to the authors.
Comment: Much has
been written and discussed about the influence of processing on the quality of
DNA in the finished product in the aftermath of the New York Attorney General
DNA barcoding investigation. The paper by Lo et al. provides some answers to
the question of what happens when DNA is subjected to extensive boiling. It
clearly demonstrates that the extent of DNA fragmentation is a function of the length
of time that the DNA is exposed to heat (i.e., the longer the DNA is exposed to
heat, the more fragmented it becomes). While smaller fragments can be found in
aqueous extracts even after boiling for an hour, it is a matter of debate how
much DNA – if any – would be recovered using general DNA barcoding methods
where most often intact gene regions between 400-1000 bp in length are required
for successful amplification.1,2
References
1. Reynaud DTH,
Mishler BD, Neal-Kababick J, Brown PN. The Capabilities and Limitations
of DNA Barcoding of Botanical Dietary Supplements [white paper]. Richmond,
CA: AuthenTechnologies; March 2015. Available at: https://gallery.mailchimp.com/2d47ec72fa1542de734a46f71/files/Reynaud_DNA_Barcoding_White_Paper.pdf. Accessed
May 27, 2015.
2. Fabricant D,
Hilmas C. NPA White Paper: DNA Barcoding for Botanical
Authentication. Washington, DC: Natural Products Association; March
17, 2015. Available at: http://www.npainfo.org/App_Themes/NPA/docs/regulatoryLegislative/White%20Paper/NPAWhitePaper_DNABarcoding.pdf. Accessed
May 27, 2015.
