Meetings

Traditional Chinese medicine

Contrasts between the widespread use of traditional Chinese medicines and the comparative lack of scientific knowledge about them were a major feature of a recent meeting held at the Royal Botanic Gardens, Kew. Peter Houghton (professor of pharmacognosy, King's College London) reports

The meeting, held on 12 June, was a joint meeting of the Royal Pharmaceutical Society, the Academy of Pharmaceutical Sciences of Great Britain, the Society for Medicinal Plant Research and the International Society for Ethnopharmacology.

UK needs greater expertise in TCM

In a plenary lecture on the impact of traditional Chinese medicine in the West, Kelvin Chan (school of traditional Chinese medicine, Hong Kong Baptist University) said that the past 10 years have seen significant improvements in knowledge of the chemistry and mode of action of Chinese medicines. TCM is more widely recognised by health professionals as having value and improvements in health of those treated are no longer attributed to placebo effect. Regulation and moves to improve quality and reduce consumer vulnerability have also occurred.

An indication of the attention now given to TCM in the Western world was an attendance of over 1,000 people at a meeting on TCM in Australia, in late 2003. Interest is growing in the academic community and from funding bodies. One third of the funds available from the US National Institute of Health for complementary medicine research are now allocated to TCM projects. Between them, Australia, Canada, US, UK and France have an estimated 14,000 TCM clinics.

Professor Chan said that 10,000 tons of medicinal “herbs” are now exported from China annually, and Hong Kong occupies a key position in the trade because of its good management infrastructure and the commitment of its government. It led the way in the recent commitment by the Chinese government to good agricultural practice, good laboratory practice and similar procedures to enhance the quality of TCM materials, since it was realised that this is critical for their acceptance in much of the world. The need for accurate and selective methods for defining quality for crude drugs and extracts was being addressed — a need highlighted by a recent analysis showing that only one of 17 samples of the drug liu shen wan was of good quality. The Hong Kong Accreditation Service was constructing standards based on 10 samples for each drug, acquired from suppliers locally and in mainland China. It took into account modern methods such as DNA fingerprinting, and functional genomic factors as well as the more conventional analytical methods.

Authenticating Chinese herbs

Monique Simmonds (Royal Botanic Gardens, Kew) described projects that she was leading on authenticating Chinese herbs. This work had arisen in response to consumer requests about TCM plants, which had increased from two in 1995 to 128 in 2002. She emphasised the ease of authenticating samples of crude drugs compared with the many patent Chinese medicines, which often contained extracts, usually in a combination from several plant species. Kew was well placed to carry out such work because of its specialist knowledge of comparative plant biology and biodiversity and its interest in sustainable use.

Professor Simmonds said that a lack of authentic specimens for plant materials, and of pure compounds for chromatographic comparisons, had driven collaborative projects between Kew and institutes in China to acquire voucher specimens of both plant material and the derived crude drug. A total of 1,700 samples had now been acquired. Chromatography (especially linked with mass spectrometry), the polymerase chain reaction and other molecular biological techniques were being used to provide multidimensional standards.

Despite TCM’s bad press because of some errors, it was being found that good material was more likely than not to be provided. Using the standards established, 120 specimens from a variety of traders had been obtained and analysed, and all were found to be correctly labelled. Tests for pesticides and heavy metals showed that all the samples were within the permitted limits.

Toxicological aspects

Discussing toxicological aspects of TCM, Paul But (Chinese University of Hong Kong) said that publicity over the past 10 years about the nephrotoxicity of TCM materials containing aristolochic acid had unfortunately resulted in the introduction of the term “Chinese herb nephrology”, implying that all TCM was risky. Nevertheless, in addition to fatalities and other severe toxic events reported from Belgium, the UK and several other countries, over 100 cases of nephrotoxicity had now been reported from China, where Aristolochia and Asarum species, which contain aristolochic acid, were dispensed under the name mu tong. The Chinese authorities had now banned several species, as happened in the UK a few years ago.

Other causes of toxicity included the wrong drug being supplied (eg, tropane alkaloid poisoning occurring when Datura metel flowers were supplied instead of those from a Paulownia species), overdose (eg, three fatalities in Hong Kong in recent years due to Aconitum toxicity) contamination with heavy metals as a result of poor processing techniques, and contamination of “herbal” products with conventional drugs. Professor But emphasised that quality control, training of suppliers and the provision of more information about the medicines could all help reduce the risk of toxic events occurring.

Studies of biological activity

Dan shen, the root of Salvia miltiorrhiza

Rudolf Bauer (head of pharmacognosy, University of Graz, Austria), described studies on the chemistry and in vitro biological activity of Chinese herbs, particularly those used for inflammatory conditions. He said that 1,318 species came into this category. He and his colleagues had screened almost 30 of these for inhibition of cyclo-oxygenase and 5-lipoxygenase, key enzymes in the formation of proinflammatory eicosanoids. Compounds isolated from the most active extracts included the diterpene tanshinones from Salvia miltiorhiza, known as dan shen in TCM, an ingredient of many prescriptions. Other anti-inflammatory compounds isolated included prenylated flavonoids from Sophora flavescens and atractylochromene from Atractylodes lancea.

Professor Bauer emphasised that the isolated compounds often had much weaker activity than the extracts. In some cases, synergy had been demonstrated by the use of isobolic graphs. In some instances, activity noted in vitro was not translated when the same extract or compound was tested in animal models.

Need for good clinical studies

The great need for good clinical studies was discussed by a panel made up of the speakers and Linda Anderson (Medicines and Healthcare products Regulatory Agency). Some trials in China were of variable quality and it was difficult for Western researchers to gain access to results because of language problems.

The panel also discussed the fate of TCM in the light of forthcoming licensing legislation on herbal products in the EU. It appears that many TCM herbs in current use will be eligible to be included under the new category of “medicines based on traditional use”.

Among a number of posters and short oral papers was a survey of the old literature showing that modern stories associated with the identity and traditional use of the herb qing hao su (the modern source of the antimalarial artemisinin) had little historical basis.