Problem statement: In 1999 two cases of kidney failure resulted from the use of a Chinese herb called Aristolochia manshuriensis (Chinese name: Guan Mu Tong) prescribed by practitioners of Chinese herbal medicine.

Methods: Botanists identified the contents of two herbal prescriptions (comprising a variety of loose dried plants) using gross morphological characters (i.e. characters visible to the naked eye). Key to the successful scientific naming of these plants was comparison with reference plant material, which included herbarium specimens whose identity had been confirmed by plant taxonomists. Once one of the ingredients, Aristolochia manshuriensis had been identified in both prescriptions, the Aristolochia material underwent chemical chromatographic analysis to check for the presence of renal toxins called aristolochic acids. These were found in both prescriptions. The patients involved underwent thorough toxicological investigation to eliminate all other possible causes of renal failure.

Outcomes and impacts: Recognising the potential severity of adverse reactions to this plant species, the then Medicines Control Agency (MCA) of the UK Department of Health passed new legislation in 2001 banning the manufacture, import, sale or supply of any unlicensed medicine in the UK which contained herbs in the Aristolochia and Mu Tong group. The RBG Kew undertook further research to improve detection methods for aristolochic acids, especially in unlicensed multi-ingredient patent herbal remedies.

Lessons: The design and implementation of scientifically rigorous herbal authentication systems are vital if herbal medicine is to be safely practised in the UK. Without such systems, herbal medicine has the potential to cause life-threatening adverse reactions. Furthermore, plant taxonomic expertise is an essential prerequisite for the construction of such herbal authentication systems.