Risk assessment and determination of aristolochic acids and heavy metals in Chinese herbal medicines

Cheung, T 2007, Risk assessment and determination of aristolochic acids and heavy metals in Chinese herbal medicines, Doctor of Philosophy (PhD), Health Sciences, RMIT University.

Document type: Thesis
Collection: Theses

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Title Risk assessment and determination of aristolochic acids and heavy metals in Chinese herbal medicines
Author(s) Cheung, T
Year 2007
Abstract There is community concern about toxic contaminants in Chinese herbal medicines. The two areas of contamination that attract most attentions are the nephrotoxic chemical, aristolochic acids found to be present in some Chinese herbs and resulting in renal failure of over 200 patients in Belgium, and heavy metals such as lead, arsenic, cadmium, mercury and chromium, which can cause systemic, CNS, neurological and developmental pathologies. Currently there is a lack of systematic information about the aristolochic acid content in Aristolochia species and related genera, nor have there been any studies on metal contamination conducted in Australia which can provide some scientific basis for assessment of potential risk of Chinese herbal medicines posed to consumers in Australia.

This research aimed at addressing these concerns by firstly carrying out a systematic measurement of the contents of aristolochic acids in some relevant raw herbal medicines (CHM) and proprietary medicines (CPM)- 27 CHM, and 7 CPM, and secondly analysing the contents of five heavy metals in 100 CHM, 50 CPM, and 5 commonly used Chinese medicinal formulae (CMF) in the form of raw herbs, and finally evaluating the potential systemic metal toxicity caused by routine ingestions of Chinese medicines in the common form of encapsulated concentrated powder extracts formulated for the treatment of seasonal allergic rhinitis by means of measuring the metal concentrations in blood collected from 71 patients in a randomised double-blind control clinical trial (RCT).

Results showed that four of the 37 CHM and two of the 7 CPM contained the banned toxic aristolochic acids. Some of these contaminated medicines could still be purchased over-the-counter in Victoria. Quantitative screening of metal contamination in CHM found that metal concentrations were much lower in the aqueous solutions than in the acid-digested samples. Almost all CHM, CPM and the 5 CMF contained the five heavy metals. Contrary to popular perception, their metal concentrations in the clinically ingested form were extremely low. Their prescribed ingested contents calculated as percentages of the universally recognised regulatory safety standards, the WHO provisional tolerable weekly intake (PTWI), would produce only small percentages of the PTWI for the metal concerned. This was true even when the metal intakes from any forms of Chinese medicines were added to the normal Australian daily dietary metal exposure. These new approaches of analysing the aqueous extractions, as well as interpretation with reference to the WHO regulatory standards and in combination with the Australian normal daily diet, are more relevant and realistic. The RCT in vivo study demonstrated no significant metal accumulation in the blood of both the real treatment group and the placebo control group, thus, attesting to the encouraging finding of the herbal medicine analysis.

In conclusion, there is still much to improve in Australia in terms of enforcing the regulation of banning the sale of Chinese herbal medicines that might contain the highly nephrotoxic aristolochic acids. On the other hand, all forms of Chinese medicines in Victoria are safe, and do not appear to pose significant health concerns in terms of metal contamination.
Degree Doctor of Philosophy (PhD)
Institution RMIT University
School, Department or Centre Health Sciences
Keyword(s) Materia medica China
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