The botany and macroscopy of chinese materia medica: sources, substitutes and sustainability

Interest in Traditional Chinese Medicine (TCM) is global. The burgeoning international trade in its crude and processed plant ingredients (Chinese materia medica - CMM) reflects demand across all sectors of healthcare, yet the identification of source plants and CMM has been overlooked for many years leading to problems in safety, quality, efficacy and sustainable sourcing. The Guide (Chinese medicinal plants, herbal drugs and substitutes: an identification guide, Leon & Lin, Kew Publishing, 2017), which forms the core of this dissertation by publication, presents a fresh approach to the identification of 226 internationally traded CMM (officially recognised in the Chinese Pharmacopoeia, CP2015) along with their 302 official source plants.

Identification criteria are developed using macroscopy, and are based on authentic reference specimens created as a result of extensive fieldwork in China. Inclusion of 99 comparative descriptions of unofficial substitute plants and drugs (including adulterants and counterfeits), with their counterparts for official species, enable key distinguishing characters to be highlighted and thereby strengthen the rigour of identifications made. The approach demonstrates that macroscopy can be used to reliably identify and differentiate over 70% of official (CP2015) CMM from common substitutes and that macroscopy is a fast and cost-effective authentication method with many applications.

The research highlights the essential role of herbarium-vouchered reference drugs in CMM authentication as opposed to the use of market-obtained drugs whose botanical identity is inherently uncertain. The research’s taxonomic review of all official species in the Guide demonstrates a significant disparity (16%) between the taxonomy adopted in the CP2015 and current plant taxonomic opinion, while a review of species conservation rankings and causal effects found that the wild populations of 23% of official species native to China (63 of 270 official species in the Guide) have become threatened as a direct result of over-harvesting for medicinal use. In addition, the research reveals the underlying causes of CMM substitution are dominated by clinician preference, followed by supply problems arising from over-harvesting of official species with unregulated markets trading in inferior or inappropriate look-alike items, together with issues of confused identification and nomenclature. Direct consequences of the inadvertent use of CMM substitutes include misleading clinical and research outcomes, serious adverse reactions and, in some cases, fatalities. Reliable identification of CMM therefore remains paramount for high quality research as well as safe and efficacious clinical practice. While for some CMM (ca. 30% of CMM in the Guide) robust identification requires analytical methods (e.g. chemical- and DNA-based ones), the research concludes that macroscopy continues to be a powerful tool for reliable and cost-effective identification of CMM in international trade.