Traditional Chinese medicines seized by Australian border officials contained a host of potentially toxic and illegal ingredients, a new DNA analysis uncovers.

Traditional Chinese medicines or TCMs have been an important part of Chinese culture and treatment for more than 3,000 years. In recent decades, TCM has become more popular outside of Asia, where people use the products alongside or as an alternative to Western medicine.

Traditional Chinese medicine products combine plant and animal ingredients that are meant to act synergistically. (Vivek Prakash/Reuters)

After Australian border officials seized herbal teas, capsules, powders and flakes, scientists at Murdoch University used the latest DNA sequencing technology to investigate what plant and animal ingredients the products contained.

The analysis revealed a plant ingredient called aristolochic acid, which is known to cause cancer and damage to the liver. They also found the potentially poisonous herb ephedra.

"We can use the latest DNA technology to investigate what's in these medicines and do a comprehensive genetic audit," Mike Bunce, a molecular biologist at Murdoch University in Perth told the Australian Broadcasting Corporation.

Other products contained nuts and soy that could trigger allergies and weren't identified in the ingredient list.

A total of 68 different plant families and four animal families were found in the medicines.

Ingredients from endangered animals found

That's not unusual since traditional Chinese medicine offers a combination of ingredients that are meant to act synergistically, Bunce and his co-authors said in the April issue of the journal PLoS Genetics, a peer-reviewed online publication published by the non-profit Public Library of Science (PLoS).

But the analysis also found traces from animals that are restricted from trade because they are classified as vulnerable, endangered or critically endangered like the Asiatic black bear and Saiga antelope.

The researchers raised concerns about mislabelling of TCMs related to:

Reduce manufacturing costs.

Circumvent customs' scrutiny.

Use of a misidentified product unwittingly.

Until now, it's been difficult to determine the biological origins of ingredients in TCMs processed into pills and powders.

Professor Chun Guang Li, a pharmacologist in the Discipline for Chinese Medicine at RMIT University, in Melbourne, agreed it's important to monitor the quality of these health products.

But he pointed to uncertainty with the DNA sequencing used in the study and suggested more tests to correctly identify ingredients at the species level.

The study's authors acknowledged that no genetic audit can detect DNA when it has been completed degraded and that other tests are needed to detect specific compounds in complementary medicines.

The researchers concluded that their method is cost-effective, accessible and can easily be adapted for other ingredients in alternative medicines.

A recent opinion piece published in the medical literature said that if TCM "is to take its place in the modern medicine cabinet, it must develop ways to prove itself." Bunce's team said they endorsed that view for both safety and medical effectiveness of the products.