Dangers in herbal medicine (continued) — DNA sequencing to hunt illegal ingredients
In continuation to last week’s post about the dangers of consuming aristolochic acid, I will add a bit more review on why Aristolochia plants are sometimes misidentified in Chinese medicine. Also, to commemorate DNA day this coming Wednesday, I will discuss the power of DNA sequencing in identifying ingredients, in this particular case, inside Chinese medicine.
(Do you know why April 25th is DNA day? In 1953, this was the day when the structure of DNA was published in the journal Nature.)
Aristolochic acid is a carcinogen (cancer-causing agent) contained in some species of Aristolochia plants. These plants were commonly used in traditional Chinese medicine as anti-inflammatory or diuretic agents until their toxicity became known.
In the early 1990’s, Aristolochia plant was misidentified and widely distributed in Belgium as slimming agents, which led to the development of kidney failure in more than 100 women, many of whom subsequently developed urinary tract cancer.
Why did misidentification of Aristolochia plant happen? For one thing, in traditional Chinese medicine, Aristolochia plant species were thought to be interchangeable, and one species was commonly substituted for another. Also, herbs are traded using Chinese pin yin names, which can be confusing at times. For example, Fang Ji can be the name of Aristolochia fangchi (Aristolochia plant species that contain aristolochic acid) or other herbs, Stephania tetrandra or Coccculus spices. In fact, the herbal weight-loss agent distributed in Belgium between 1990 and 1992 contained Fang Ji, but instead of Stephania tetrandra plant, it contained Aristolochia fangchi.
Traditional Chinese medicines are complex mixture of ingredients often grounded into powder. As a result, it is extremely difficult to analyze their compositions. To make the matter worse, there are concerns that some medicines may be mislabeled intentionally (to reduce manufacturing cost by including cheaper ingredients or to evade customs check) or even unintentionally (by misidentification of products). Some medicines may contain toxins or endangered species, so that for both safety concerns and biodiversity conservation, new technique must be developed in order to detect ingredients efficiently.
A team of scientists in Australia are doing just that. The team is focusing on high-throughput, next-generation DNA sequencing technique that can identify all of the ingredients inside the medicine simultaneously. This approach contrasts greatly with previous methods which focused on identifying one specific target at a time and which could only detect compounds rather than specific species of plants or animals.
As a trial of their new method, the scientists studied the components of 15 traditional Chinese medicines that were confiscated at the Australian borders by the customs. The result showed that 31% of the samples contained Aristolochia plants (although the scientists note that further study is needed to test for the presence of aristolochic acid). In addition, four of the samples tested contained DNA from endangered animals, revealing that illegal hunting and trafficking of these animals still persist.
Shockingly, the study exposed that 78% of the samples were mislabeled; they contained DNA from animals that were not identified on the labels. For example, one product claiming to be made from 100% pure Saiga antelope horn powder (which, by the way, is illegal to trade as the animal is critically endangered) also contained significant amounts of goat and sheep DNA. The scientists who conducted the study warn the consumers to be cautious.
To be fair, the samples in the study were suspicious to begin with and that is why they were seized by the customs in the first place. To repeat the introduction of last week’s post, traditional Chinese medicines have been used for thousands of years and their effectiveness is getting international attention. In addition, many of the traditional Chinese medicines are well studied, owing to universities and other institutions dedicated to studying such medicines. Therefore, I want to emphasize that the majority of the traditional Chinese medicine on the market today are probably safe and legal. With that being said, it is still a good practice for consumers to know the origins of their medications and judge whether the source can be trustworthy.
I hope you found this post useful. See you next week! 🙂
PS: For readers who are interested in learning more about aristolochic acid, you can find more information on the document provided by the International Agency for Research on Cancer (IARC), which also lists the species of Aristolochia plants that contain aristolochic acid.
Molecular Structure of Nucleic Acids
Molecular Structure of Deoxypentose Nucleic Acids
Molecular Configuration in Sodium Thymonucleate
Deep Sequencing of Plant and Animal DNA Contained within Traditional Chinese Medicines Reveals Legality Issues and Health Safety Concerns
PLANTS CONTAINING ARISTOLOCHIC ACID