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Plant and Animal DNA Provides Peek at Traditional Chinese Medicine Ingredients

NEW YORK (GenomeWeb News) – An Australian research team found material from endangered animals, potentially toxic plants, and/or ingredients not included in product descriptions when they used sequencing to test more than a dozen traditional Chinese medicines (TCMs) in a study appearing online last night in PLoS Genetics.

The team did high-throughput plastid gene and ribosomal RNA gene sequencing to determine the plant and animal constituents in 15 TCM powders, pills, and potions seized at Australian airports and seaports by the country's customs and border protection service. The analysis uncovered several examples of products that were mislabeled or contained material from animals that are trade-restricted due to conservation laws.

Among diverse plant ingredients found in the samples, meanwhile, the investigators identified plants from genera that contain potentially toxic compounds.

"Some of the TCMs contained plants of the genus Ephedra and Asarum," senior author Michael Bunce, head of Murdoch University's ancient DNA research laboratory, said in a statement. "These plants contain chemicals that can be toxic if the wrong dosage is taken, but none of them actually listed concentrations on the packaging."

As the use of TCMs continues to expand globally, some have expressed concerns over their safety and effectiveness, Bunce and his co-authors explained, particularly since it can be tricky to know for certain what is in some mixtures on the market.

"[D]ue to the proprietary nature of TCM manufacture, coupled with a lack of industry regulation, the biological origin of contents can be difficult to determine with confidence, leading to questions regarding TCM quality, efficacy, and safety," they wrote.

Along with worries over the possible presence of toxins, allergens, or drugs found at an undisclosed concentration in TCMs, there are food labeling and legal issues surrounding the medicines too. That's especially true for preparations that rely on plant or animal-derived ingredients from protected or endangered species regulated under the international Convention on International Trade in Endangered Species, or CITES.

With such issues in mind, Bunce and his colleagues decided to try using high-throughput sequencing to simultaneously catalogue the plant and animals in 28 powders, pills, herbal teas, and bile flakes that had been seized by officials at Australian borders or seaports.

Fifteen of the samples contained enough high-quality DNA after the initial sample preparation steps and careful quality control testing to take forward to sequencing-based testing.

Using the Roche 454 GS Junior, researchers did multiplexed, deep sequencing of a portion of the trnL plastid gene to identify plant families in 13 of the TCMs. Similarly, animal-derived ingredients in nine of the TCMs were classified by targeted 16S mitochondrial gene sequencing.

When they compared the sequences to plant and animal sequence databases, the investigators found four TCMs containing either Asiatic black bear or Saiga antelope, which are protected as vulnerable or endangered species under CITES regulations.

Some TCMs also had sequences from cow, goat, sheep, deer, water buffalo, and Asiatic toad, though these were not always included on the English or Chinese ingredient lists.

The ingredients were even more complicated and diverse in the 13 samples tested for plant ingredients. There, researchers identified representatives from 68 different plant families, with one of the TCMs containing plants from as many as 16 families.

Among the most common plant genera identified were those representing licorice root and mint. Asarum, or wild ginger, also turned up in almost one-third of the samples—a potential concern, according to researchers, since some Asarum species produce the toxic compound aristolochic acid.

One TCM had sequences resembling those in the Ephedra genus. Plants in this genus can be toxic outside of a narrow dose range, researchers explained, leading to a 2004 ban on Ephedra by the US Food and Drug Administration.

Researchers cautioned that the level of analysis used in the current study was not refined enough to identify individual plant species. Instead, most plants classified at the genera and/or family level. They also noted that metabolomic analyses are needed to determine which TCMs, if any contain pharmaceutically active plant products.

Even so, from their initial analyses of these TCMs, authors of the study argued that similar sequencing-based methods will likely find favor for those interested in figuring out what's in other alternative medicines as well.

"[T]he approach described here is … cost-effective, accessible, and can be easily adapted to profile the molecular constituents of other biologically derived complementary and alternative medicines," they wrote.

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