What is “Daodi” Medicinal Material?

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What is “Daodi” Medicinal Material?

By Eric Brand, Zhongzhen Zhao, and Ping Guo

Throughout history, Chinese herbal medicine has been deeply influenced by the natural resources and culture of China. Natural resources such as wild and cultivated plant resources are inseparably connected to the development of Chinese medicine. Agriculture and trade have long played a pivotal role in the production and dissemination of herbal medicines in China, allowing access to medicinal materials sourced across a broad geographic area, both domestically and abroad. Historically, widespread trade in herbal medicines allowed practitioners in disparate regions to share the same medicinal substances, and the existence of a common written language allowed ancient Chinese practitioners to develop a vast body of literature to share medical perspectives and theories.

The great geographic diversity of China provided ancient practitioners with abundant natural resources to explore, and many items eventually became integrated into trade and systematic Chinese medical theory. Over time, agriculture and trade gradually gave rise to unique developments such as the notion of daodi medicinal material, which is a concept that associates authenticity and quality with specific regions and production practices. In the 20th century, rapid modernization and the constant challenges of sustainability have led to new developments to preserve China’s natural resources, such as Good Agricultural Practices (GAP) that are customized to specific crops used in Chinese herbal medicine.

As a unique concept in Chinese medicine, daodi is a term that lacks a perfect English translation when used to describe medicinal material. While it is superficially similar to the popular French concept of terroir, the concept of daodi is slightly more complex because it is intricately related to clinical efficacy as well as macroscopic qualities such as taste and appearance. Thus, the term daodi is generally preserved by using pinyin in the West, like other Chinese medical terms such as qi, yin, and yang.

The word “dao” in “daodi” was originally used to describe administrative districts in the Chinese empire, similar to the modern use of the word “province”. The word “di” is generally related to soil, geography, and landforms. According to a concise definition proposed by experts at the 390th Xiangshan Scientific Conference in Beijing in 2011, daodi medicinal material is:

“Medicinal material that is produced and assembled in specific geographic regions with designated natural conditions and a specific ecological environment, with particular attention to cultivation technique, harvesting, and processing. These factors lead to quality and clinical effects that surpass items of the same botanical origin that are produced in other regions; thus, such items are widely recognized and enjoy a good reputation.”

In Chinese herbal medicine, about 500 medicinal materials are commonly found in trade, and approximately 200 of these have specific daodi forms. Herbs with daodi specifications have high economic value and account for about 80% of the Chinese herbs in trade.

 

Rooted in a history of clinical practice

Chinese medicine has accumulated abundant clinical experience over a long period of time, and the perspective that some medicinal materials are superior in quality is rooted in this tradition. There would thus be no concept of “daodi” medicinal material without the clinical experience of Chinese medicine.

Production areas have long been emphasized in historical texts dedicated to medicinal materials. The Divine Husbandman’s Classic of Materia Medica (Shen Nong Ben Cao Jing) was the first text to discuss the importance of production regions; many medicinal names within it were related to specific geographic regions in ancient times, and further notes on quality differentiation were added in the Annotated Materia Medica Classic (Ben Cao Jing Ji Zhu). In 659 AD, the Tang Dynasty Newly Revised Materia Medica (Xin Xiu Ben Cao) emphasized the importance of production regions with the statement: “if medicinal material is not produced from its native environment, it will be the same in substance but will differ in effect.”

The famous Tang Dynasty author Sun Simiao suggested that excellent treatment results can only be obtained through the use of daodi medicinal materials, stating:

“Ancient doctors depended on medicinals produced from the proper production areas. Therefore, if they treated ten patients, they achieved results in nine. Although contemporary doctors understand the pulse and prescriptions, they are not familiar with the proper production regions, harvest time, and quality of medicinals. Thus, they only achieve results in five or six cases out of ten.”

This concept was further emphasized in the Extension of the Materia Medica (Ben Cao Yan Yi) from the Song Dynasty, with the statement: “All medicinals used must be from suitable production regions.” By the time of the Ming Dynasty, daodi specifications for 268 medicinals were formally recorded in the text Essentials of Materia Medica Distinctions (Ben Cao Pin Hui Jing Yao).

 

The relationship between botanical varieties and daodi materials

The diverse geographic conditions of China are a key natural resource in the formation of daodi medicinal materials. Genetic differences between species and varieties of plants are often important factors related to daodi medicinal materials. For example, the daodi form of shan yao (rhizome of Dioscorea) is derived from Dioscorea opposita Thunb. Also known as huai shan yao, this species is thought to be superior when grown in Henan, and it is referred to as tie gun shan yao in commerce due to its tight rod-like shape. Non-medicinal, culinary varieties of shan yao are also sold in Asian grocery stores, but these culinary varieties are derived from other species of plants in the Dioscorea genus and are not used in medicine. In ben cao literature, the differences between medicinal shan yao and culinary varieties of shan yao were discussed as early as the Ming Dynasty.

Chinese herbal medicines have a long history of use, with diverse and complex origins. In the 2010 Chinese Pharmacopoeia, about 25% of the medicinals listed can be derived from two or more sources. In some cases, the traditional names given to different forms of a given herb correspond to differences in the botanical species used, such as bei wu wei zi (Schisandrae Chinensis Fructus) and nan wu wei zi (Schisandrae Sphenantherae Fructus), which are often described as “northern” and “southern” forms of wu wei zi (Schisandrae Fructus).

 

The influence of environmental conditions on daodi materials

Bioactive constituents are affected by environmental factors such as soil, climate, humidity, and light, which directly influence the secondary metabolites of plants. In ancient times, differences based on environmental conditions were noted in the Chinese saying that “tangerines that grow south of the huai river are tangerines, when grown north of the huai river they are bitter oranges; the leaves are similar but the flavor of the fruit is different.”

In the case of chuan xiong (the rhizome of Ligusticum chuanxiong Hort.), the word “chuan” in its name reflects the fact that its daodi medicinal material is produced in Sichuan province. It has a cultivar known as fu xiong (Ligusticum chuanxiong Hort. cv. Fuxiong) that is grown in Jiangxi province, yet it goes a long time without flowering and rarely sprouts, yielding fleshy rhizomes that contain less volatile oil and have a lower ligustrazine content when compared to the item grown in Sichuan.

Over the course of time, environmental and other changes in China have caused the recognized daodi regions to change for some herbs. For example, wild trees in Yunnan were previously used as the source material from which fu ling (Poria) was collected, thus fu ling from Yunnan was considered to be the daodi material; now that the poria fungus is cultivated, the primary form on the market comes from Hebei province. Similarly, san qi (Radix Notoginseng) is also called “tian qi” because it was once produced in the “tian zhou” region (in modern-day Guangxi province). However, at present the Wenshan county region of Yunnan province is considered to be the main daodi production area for san qi.

In the case of Asian ginseng, changes in its historical distribution due to environmental changes and over-collection led to changes in the region that was perceived to be daodi. Originally ginseng was distributed across a wider geographic area than it is found today, and ancient texts praised the ginseng produced in the shang dang region (modern-day Shanxi province). Records from the Song Dynasty illustrate that a plant in the Panax genus was indeed produced in this area, but the ginseng resources in the region were depleted due to overharvesting and deforestation, causing the daodi production region to move to northeastern China.

 

The influence of cultivation techniques on daodi medicinal material

Agricultural progress was interrupted when China suffered from extended wartime conditions in the Southern Song and Yuan Dynasties, but advances in the cultivation of medicinal plants followed in the Ming Dynasty with the support of government agricultural policies. As new literary works flourished and agricultural techniques matured, cultivated plants became the primary source of most daodi medicinal materials.

Rehmannia is a classic example of a daodi medicinal that is has been subjected to long-term cultivation. Known as one of the “four great huai medicinals,” it has been cultivated in the huai qing fu region of Henan province for centuries. Techniques for cultivating Rehmannia are described in the Tang Dynasty text Formulas Worth a Thousand Gold Pieces (Qian Jin Fang), and in the Compendium of Materia Medica (Ben Cao Gang Mu), Li Shizhen notes that “ancient people cultivated it from seed, contemporary people propagate it from the roots.” This asexual cultivation technique is still used today, and the cultivar that has emerged in that region has superior characteristics in terms of its growth habits and chemical constituents.

 

Other factors

The use of pao zhi (medicinal processing) is another factor in the formation of daodi medicinal material. For example, in the case of the herb fu zi (Aconiti Radix Lateralis Praeparata), the daodi material does not simply come from a specific region, it also incorporates proper pao zhi methods for processing. In The Chinese Pharmacopoeia (2010), four different processed forms of fu zi are described.

Furthermore, many foreign medicinals that have been introduced into China also have daodi specifications, and in some cases these items have been cultivated in China successfully. For example, the herb mu xiang (Aucklandiae Radix) originally came to China from India, and was called guang mu xiang because it entered trade via the city of Guangzhou. Later on, it was successfully cultivated in Yunnan province in China, and today the product from Yunnan (called “yun mu xiang”) is regarded as the main daodi material in trade.

The subject of daodi medicinal materials provides a unique vantage point to look into the complex history of Chinese medicinal quality assessment. Since medicinal quality is intimately connected with natural wild and cultivated plant resources, the subject of daodi medicinal material is inseparable from the topic of natural resources.

 

Natural resources and GAP cultivation

China has very rich natural resources due to its vast size and diverse topography. A national survey on natural resources that was conducted from 1985 to 1989 found that nearly 11,000 plants are used medicinally in China. In China, the implementation of GAP (Good Agricultural Practices) for Chinese herbal medicines is imperative. In 2002, China's State Food and Drug Administration published draft standards for good practices in Chinese herbal medicine production. The aim is to establish standards at all the links in the supply chain, starting from the farm level, in order to assure “safety, quality, consistency, and controllability”. In 2003, the WHO (World Health Organization) published a draft guidance document for GAP standards, and in 2004, further GAP initiatives were advanced by the EU, Korea, and Japan.

As of 2009, nearly 800 production sites had been established for Chinese herbal medicines in China, with a total of approximately 500 species in cultivation. About 20% of the species in trade account for about 80% of the total volume of trade, and many commonly used herbal medicines are primarily cultivated. As of May 23, 2014, 109 GAP plantation sites had completed the national certification process, with sites established for 69 different medicinal materials in 23 provinces.

Nonetheless, the GAP model is not suitable for all medicinal materials; wild resources and small-scale growers require management approaches suited to their individual circumstances. At present, cultivated sources only account for about ¼ of the total number of plant varieties used in Chinese herbal medicine, and the path towards modernizing the production of Chinese herbs will be a long work in progress. Ultimately, the dream of sustainable development in the Chinese medicine industry depends upon the sustainable use of wild resources and vigorous efforts to increase the scope of cultivated medicinal plant varieties.

In addition to the ecological preservation of medicinal plant resources, attention is needed to preserve the cultural resources that lie at the heart of Chinese materia medica. The ben cao tradition provides a rich record of knowledge that has been gradually refined for centuries, opening a window into the cultural tradition of scholarship and textual research that defines Chinese medicine.

In recent decades, exploration of ben cao literature has led to dramatic medical discoveries, such as the isolation of the anti-malarial drug artemisinin from qing hao (Artemisiae annuae herba). Ben cao texts have documented the assimilation of new medicinal plants for centuries, and are rich with information on processing methods, botanical varieties, production areas, and clinical applications. Additionally, ben cao literature illustrates important developments in the broader history of natural sciences in China, such as knowledge related to the processing of minerals and early attempts to create systematic botanical classification schemes in the pre-Linnaean era. Nonetheless, the overall significance of ben cao literature remains largely unknown outside of the Chinese medical community and its related scientific circles, and represents an important area for further research.

The historical prominence of agriculture and trade in China allowed medicinal materials to gradually develop a complex culture in terms of quality discernment, regional specialties, and processing methods. Distinctive features such as the processing methods of pao zhi and the quality assessment methods applied to daodi medicinal materials are proving to be a rich resource for scientific research as Chinese medicine moves into the 21st century. The future of Chinese materia medica research thus depends upon a multidisciplinary approach that protects the past while embracing the future.

 

References

1) ZZ Zhao, P Guo, E Brand. The formation of daodi medicinal materials. Journal of Ethnopharmacology. 2012, 140 (3):476-481

2) ZZ Zhao, HB Chen. Chinese Medicinal Identification: An Illustrated Approach. Taos: Paradigm Publications. 2014

3) ZZ Zhao, ZT Liang, K Chan, GH Lu, ELM Lee, HB Chen, L Li. A unique issue in the standardization of Chinese Materia Medica: Processing. Planta Medica. 2010, 76: 1975-1986

4) Pan, F., 2011. Daodi medicinal material is the essence of Chinese medicine—a review of the 390th session of Xiangshan Science Conference. Science Times, February 28, 2011. Beijing, China.

5) Chinese Pharmacopoeia Commission. Pharmacopoeia of the People’s Republic of China, 2010 edition. Beijing: China Medical Science and Technology Press. 2010

6) SM Fang, HD Zhang. Studies on the origin of the traditional Chinese drug Fuxiong and its relationships with Ligusticum chuanxiong and L. sinense. Acta

Phytotaxonomica Sinica 1984, 22: 38–42

7) GS Li, CH Liu, HS Wang, LJ Zhang. Assaying of content of catalpol

in Rehmannia glutinosa from different origins. Chinese Traditional and Herbal

Drugs 2002, 33: 126–128

8) ZZ Zhao. The World of Ben Cao. Hong Kong: Wanli Publishing Group. 2014

 

Eric Brand

A Chinese medicine practitioner from the United States, Eric Brand is the author, co-author, editor, and translator of a variety of modern and classical texts. He is currently completing his PhD in pharmacognosy and is the owner of Legendary Herbs. Eric serves as a Chinese medicine advisor to the American Herbal Pharmacopoeia and is the current Chair of the U.S. Delegation for the ISO TC 249 committee on international standards in traditional Chinese medicine.

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Ping Guo

Dr. Ping Guo is a lecturer of the School of Chinese Medicine at Hong Kong Baptist University, specializing in Chinese materia medica and medicinal authentication. He holds a master’s in pharmacognosy and doctoral degree in Chinese materia medica from the Chengdu University of Traditional Chinese Medicine. He has been engaged in teaching and research activities in China and overseas higher education institutions of TCM since 1989.

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Zhongzhen Zhao

Prof. Zhongzhen Zhao is Associate Dean of the School of Chinese Medicine at Hong Kong Baptist University and has been published extensively in peer-reviewed scientific journals and books. He obtained his doctoral degree at the Tokyo University of Pharmacy and Life Science and has long been deeply engaged in Chinese medical research, education, and international exchange. Prof. Zhao also serves on the Scientific Committee and International Advisory Board of the Hong Kong Chinese Materia Medica Standards, amongst other committees and councils.

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