DNA sequencing reveals unexpected ingredients in Chinese medicines
Some traditional Chinese medicines (TCMs) contain bits of endangered animals, potentially poisonous plants, and unlabeled ingredients, according to a study conducted at Murdoch University (Perth, Western Australia).1 The study falls on the heels of the federal government's decision to register Chinese medical practitioners in the same way as other health professionals.
The researchers, using second-generation DNA sequencing, analyzed ingredients in 15 TCMs and found that three-quarters of them contained undeclared animal products, including the critically endangered Asiatic black bear, plus water buffalo, domestic cow, and deer species, explains Mike Bunce of Murdoch University, who led the study. Another product, which claimed to contain 100 percent Saiga antelope (also critically endangered) horn powder, also contained goat and sheep DNA. Bunce's team also identified material from up to 30 plant families, including some that are highly allergenic and many of which were not labeled on the packaging. One of note is the Aristolochiaceae plant family—known as wild ginger—which contains Aristolochic acid, a carcinogen.
Second-generation DNA sequencing involves pyrosequencing, which enabled Bunce and his team to analyze lots of DNA from the samples simultaneously. "Literally millions of DNA sequences can be determined in parallel," Bunce told BioOptics World. Using a commercial system (Roche's GS Junior benchtop sequencer), the team imaged hundreds of thousands of sequences on a surface about the size of a coin, he explains. Then, the A, T, C, and G DNA bases were washed over this surface (many times in a specific order), and the sequencer's CCD camera picked up flashes of light when either A, T, C, or G incorporated into the DNA. These light flashes were then converted into raw DNA sequences, he says, and compared to databases of known animal and plant DNA sequences.
The TCMs tested in the study were confiscated by Australian customs for breaking environment laws, and were not registered medicines. "But I would not be surprised if those products were for sale in Australia," says Bunce.
1. M.L. Coghlan et al., PLoS Genet., 8, 4, e1002657, doi:10.1371/journal.pgen.1002657 (2012).
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