Using DNA forensics to uncover the mysteries of the medicinal orchid trade in Hong Kong
Many people are fascinated by orchids because of their beautiful flowers. However, when processed orchids or their parts, such as leaves, tubers and roots, are sold as traditional Chinese medicine (TCM) in the market, it is practically impossible to make the link to how they looked originally when alive. As a matter of fact, certain medicinal orchids are among the most expensive TCM in Hong Kong. The price of ‘Herba Dendrobii’ (石斛) can reach HK$2,800/tael or HK$74/gram.
There are more than 5,000 TCM retail shops in Hong Kong, and according to our market surveys, most have medicinal orchids available for purchase. The most common orchid products are Herba Dendrobii (石斛) and Rhizoma Gastrodiae (天麻), but Rhizoma Gymnadenia (手參) and Rhizoma Bletillae (白芨) are also available.
All orchid species are listed in the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES), a global treaty that regulates the trade in endangered wildlife. Therefore, import and export of wild orchids is restricted in Hong Kong. However, regardless of that, continuous large demand and resulting high prices have fuelled over-collection of wild orchids throughout the South China and Indo-Burma region, despite protections under international and local regulations.
There are safety concerns associated with the use of TCM. For example, only limited information is typically available about the plants included in these medicinal products. TCM are generally sold in the market accompanied only with their common names, but a single common name can sometimes refer to several or even many different species that might have varied medicinal properties, if any at all. For example, Herba Dendrobii (石斛) comprises the stem of any of a number of different Dendrobium species. Little do most users know that the genus Dendrobium has over 1,500 species and that many are considered medicinal. But how many exactly is the million-dollar question.
So, what species are being sold as TCM in the local market? Where are they from? Are they of cultivated origin or were they collected from the wild? Is the trade sustainable? To answer these questions, KFBG has turned to DNA forensics to uncover some of the important mysteries surrounding this trade and, by implication, its conservation impacts.
It did not take long for our first challenge to surface: extracting DNA from TCM is difficult because many of the plant products from which they are made have been treated with high temperatures or chemicals, and so the remaining extractable DNA is typically highly degraded. We tried different techniques to isolate DNA from the samples, and we even experimented with methods developed for extracting ancient DNA from fossils.
DNA identification for these TCM samples also relies on the existence of reference data based on plants whose identities have been verified by an orchid expert. Therefore, we built an orchid DNA database using KFBG’s well curated collection of orchids from across tropical Asia.
The resulting DNA data suggest that these TCM are indeed derived from orchids, and that species from several notable orchid genera (in particular Dendrobium, Bulbophyllum, Gastrodia, Gymnadenia and Bletilla) are routinely involved. Although most shops claim their products are authentic, we found multiple different species being offered under the same name by different shops. Some TCM are likely sourced from wild plants because, according to our DNA analysis, multiple species are usually present even in small packages. However, many consumers likely do not know they are buying protected orchids for medicine.
The market survey and DNA work is ongoing, and we hope to gain more understanding of the medicinal orchid trade in Hong Kong. We suggest TCM shops in Hong Kong should provide more labelling information about species (both common name and scientific name), country of origin, and whether sourced from the wild or artificially propagated to help clarify that the trade is legal, transparent and sustainable. Consumers would also benefit from more information about these TCM products and put them in a position to say “no” to wild-collected orchids.