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Seeking the Evidence for Chinese Medicine

By Dave Hawkes

By looking for active ingredients in traditional Chinese medicines, ethnopharmacologists are finding evidence for their efficacy.

Evidence-based medicine is exactly that – treatments based on solid knowledge of both their safety and efficacy. But a number of popular treatments, such as different forms of traditional or herbal medicine, don’t fit within this evidence-based framework. The most well-known of these is traditional Chinese medicine (TCM), which enjoys worldwide sales in the billions of dollars.

TCM has a number of issues that detract from its widespread acceptance, such as microbial or heavy metal contamination, inconsistent quantities of active ingredients, the use of endangered species and finally, with some TCM ingredients (such as Chinese mothwart) containing more than 140 biological compounds, increased risk of side-effects.

However, there is some evidence from small, preliminary studies that certain traditional Chinese remedies may provide novel treatments for a range of conditions. So how can we develop these potential treatments based on TCM so that they can be incorporated in evidence-based practice?

Ethnopharmacology can be broadly defined as the study of traditional medicines from a pharmacological perspective. There have been a number of success stories using this approach of examining traditional remedies and identifying and synthesising the active constituents. For example, the bark and leaves of the willow tree had been used to reduce pain and fever for more than 2000 years before Edward Stone extracted salicylic acid from willow bark 250 years ago. Salicylic acid is the active metabolite of a drug we commonly know as aspirin.

A more recent example is prostratin. During a research trip to Samoa, Dr Paul Cox was shown how traditional healers use the bark of the mamala tree to make a potion for the treatment of hepatitis. Analysis of mamala bark, undertaken with the consent of tribal elders, discovered a biological compound called prostratin that was found to be a potential treatment for another virus, HIV, due to its ability to expose viruses hidden to drug treatment. Phase 1 clinical trials of prostratin are currently in the planning stage.

These examples show that there is a clear pathway from traditional medicine to evidence-based treatment, but will this approach work for TCM? In a recent article published in Trends in Pharmacological Sciences we examined the science behind the TCM remedy compound danshen formula (CDF), which is composed of three separate herbs – danshen, sanqi and bingpian – and is used in the treatment of hypertension.

The evidence for the effectiveness of CDF, which contains more than 100 biological compounds, on hypertension is small but there is enough information to indicate that it has an effect that is greater than placebo. Recent studies have identified three active ingredients in CDF – tanshinone IIA, salvianolic acid B and ginsenoside Rb1 – that can almost fully replicate the effects of CDF on biological markers for heart attack in an animal model.

In short, the evidence suggests that although there are more than 100 biological compounds in CDF you only need three to reduce the risk of hypertension and heart attacks.

CDF gives an example of a traditional Chinese medicine that is on the path to becoming an evidence-based medicine. While it is not yet known whether CDF or the isolated biological compounds will become an evidence-based medical treatment, it is going through the process of being examined and tested by the same scientifically accepted assessment procedures required of other pharmaceutical products.

It is often easy to dismiss alternative treatments for lacking an evidence base. Such criticisms are often valid, but when researchers begin using good scientific practices to examine traditional medicines it should be encouraged. You never know, they might be identifying a cure for AIDS, or even just for a hangover.

Dr Dave Hawkes is a postdoctoral researcher at The Florey Institute for Neuroscience and Mental Health in Melbourne. Joanne Benhamu is an executive member of Friends of Science in Medicine.