Approximately 1,000 plant species are commonly used in Chinese medicinal preparations. More than three-quarters of these are collected from the wild. The demand for medicinal plant material has grown at an annual rate of 9% over the past two decades. The threat posed by overexploitation and the measures which need to taken for the conservation and cultivation of medicinal plants are highlighted using Atracylodes lancea as an example.
Medical and pharmaceutical traditions of China have evolved over the centuries as essential parts of its civilization and are widely recognized today as representing its rich cultural and scientific heritage. As this medical knowledge and expertise were built on a land endowed with an abundance of varied flora, it is not surprising that medicinal plants play a central role in Chinese medicine and the country's achievement in the utilization of its native plants in health care delivery has been admired and acknowedged throughout the world.
According to a recent study (He and Cheng, 1990), the total number of species of medicinal plants used in different parts of the country add up to over ten thousand. According to a Chinese proverb, "Every plant is a medicinal herb."
The official Pharmacopoeia of People's Republic of China lists 709 different drugs. Among these, only a little more than 40 items are animal and mineral products. Others are all derived from plant material. Plant material accounts for more than 80% of the drugs sold on the market. Approximately 1000 species of plants are now commonly used in Chinese medicine and about half of these are considered as the main medicinal plants which are in particularly common use. Material from these 1,000 species is harvested and marketed extensively. Medicinal plants are distributed over a wide geographic area ranging from 50oN (Helongjiang province) to 10oN (Hainan province) and from 80oE to 130oE.
The government has introduced a series of laws, regulations and rules to provide guidelines for and to control the collection, cultivation, production, certification, registration and marketing of medicinal plants in order to promote the development of Chinese medicines in the most appropriate manner and to protect public health and safety.
If we consider the most common ailments affecting wide sections of the population, viz. cancer, cardiovascular diseases, hepatitis, influenza and various kinds of fevers, then the most popularly used medicinal plants are either those in the group used for increasing the person's immunity and resistance to diseases, e.g. Panax notoginseng, Panax quinquefolium, Cordyceps sinensis, Eucommia ulmoides, Gastrodia elata, Ganoderma lucidum etc. or are among other medicinal plants used for specific conditions, e.g. Dioscorea spp., Salvia miltiorrhiza, Astragalus membranaceus var. mongholicus, Glycyrrhiza uralensis and Bupleurum chinense.
It should be remembered, however, that prescriptions in the Chinese system of medicine nearly always consist of material from several different plants.
Whereas both traditional Chinese medicine and western medicine form part of today's health care system in China, the former is more popular among the country's population at large. The state offers assistance and support to the cultivation of medicinal plants and, at the same time, promotes the development of an integrated health care delivery system which combines traditional Chinese medicine with modern western medicine. Most large hospitals offer treatment based on both systems and it is very common for patients to receive both Chinese medicines and western medicines for their illness. Sometimes they take both kinds of medicines at the same time and sometimes alternatively.
People suffering from ailments for which there is no satisfactory treatment in western medicine, no matter whether they live in rural areas or in cities, always look for alternatives based on traditional Chinese medicine. Many studies comparing the relative efficacies of Chinese and western medicines for a range of conditions, both chronic and acute, have established the superiority of the former (NABCMD, 1989). Examples of chronic conditions include chronic anaemia, lupus erythematosus, stomach cancer and ABO haemolytic disease of new-born babies. Examples of acute conditions include mortality from haemorrhagic fever caused by wild mouse, myocardial infarction, pancreatitis, and cholangitis.
Discovery of the anti-malarial drug Qinghaosu from Artemisia annua and the medicine for hepatitis derived from Swertia milensis have further proved the future potential of Chinese medicinal plants. Plants used in Chinese traditional medicine which have shown promise as potential sources of anticancer and anti-HIV compounds include Glycyrrhiza uralensis, Ligusticum chuanxiong, Astragalus membranaceus var. mongholicus, Schisandra chinensis , Atractylodes lancea, Acanthopanax senticosus, Panax ginseng, Lithospermum erythrorrhizon, Senecio scandens and Coptis chinensis (Zhun, 1991).
During the period from 1979 to 1990, forty-two new Chinese medicinal preparations appeared on the market (Song, 1992). Among them 11 are for cardiac diseases, five for cancer and six for ailments of the digestive system (Huang, 1990). The green movement and the current trend of "coming back to the nature" have led to a renewed interest in traditional medicinal plants. A new aspect, namely the use of fresh medicinal plant material, is worth mentioning. Recent studies carried out at the Jiangsu Institute of Botany (Nanjing Botanical Garden, Mem. Sun Yat-Sen) on the efficacy of fresh herbs in treatment for the skin diseases, herpes, caused by viruses. A Chinese medicine named "Eliherpes" has proved particularly effective in the treatment of herpes zoster, herpes simplex and sexual herpes. In a clinical trial involving more than 200 patients, it was found to be effective in 94.36% of the cases. The medicine is inexpensive, safe to use and easy to administer. It provides quick pain relief and rapid healing without sequelae. This new approach using fresh herbs has been developed and applied for treating patients in some hospitals in Nanjing city already.
Until now, the major part of plant material used in Chinese medicines has originated from wild sources. Among the 1,000 commonly used medicinal plants, 80% in terms of number species and 60% in terms of total quantity have come from wild sources. Overexploitation is a problem common to all medicinal plants. For most species, the natural reserves are exhausted within 10 to 20 years of collection. For some species the supplies from the wild last only for three or four years, after which no more commercial production is possible. It should be noted that the loss of genetic variation within a given species is usually much more serious and occurs much earlier than the total extinction of the species itself. For example, the content of diosgenin in Dioscorea zingiberensis collected during expeditions in the 1950s averaged only 7% whereas the maximum recorded was about 17%. In material collected during the 1980s the content was reduced to such an extent that even 4% was considered as high. When the medicine using Swertia milensis was developed for the treatment of hepatitis, a shortage in the supply of plant material appeared within three to four years (Wang, 1992).
In the past, the distribution of Glycyrrhiza uralensis was mainly concentrated in Inner Mongolia. In the 1950s G. uralensis grew over an area of 1.2 million ha. By 1981 this was reduced to only 330 thousand ha. The center of western growing area had therefore moved to the Xinjiang autonomous region (Yuan, Wang and Lu, 1992). The situation is not any better in the eastern growing area either. In the 1960s the plain of Nenjiang river was famous for its G. uralensis population. Twenty years later there were no bushes with any commercial value left in this area. Preliminary statistics indicate that approximately 6,000 tons of G. uralensis are exported annually and the domestic consumption amounts to several thousand tons (Fu and Du, 1987).
A similar situation of shortage has also been observed for the following species: Cistanche deserticola, Cordyceps sinensis, Asarum heterotropoides var. mandshuricum, Phellodendron chinense, Eucommia ulmoides, Magnolia officinalis, Gastrodia elata, Ephedra sinica, Acanthopanax senticosus, Bupleurum chinense, Paris polyphylla, Atractylodes lancea and Notopterygium incisum.
The depletion of resources has accelerated with increasing demand for Chinese medicinal preparations both at home and abroad. Since 1979 the demand has increased at a rate of 9% per year. In 1987 the total production had reached 650 thousands tons (Chinese Yearbook of Pharmacology, 1987). There are altogether more than 600 industrial plants producing over 4,000 composite drugs in 40 different formulations. In 1978 the total value was RMB 3.6 billion. In 1990, the total quantity was 20 thousand tons and the total value RMB 5.5 billion. By 1992, this had increased to RMB 11 billion. Chinese medicinal preparations are exported to more than 100 countries and the total value of exports is in the region of 100-200 million U.S. dollars (Li, 1992).
The only solution to this rapid exhaustion of resources is cultivation. Since the 1980s there has been a rapid increase in the area cultivated with medicinal plants. In 1984 the total land area devoted to medicinal plant cultivation was 380 thousand ha which is about 161% of that in 1981.
At present there are more than 250 species of medicinal plants being commercially cultivated. Among them about 60 species have performed particulary well under cultivation (Institute of Medicinal Plant Development, 1991). The main crops cultivated are as follows: Gastrodia elata, Panax ginseng, Panax notoginseng, Cordyceps sinensis, Coptis chinensis, Eucommia ulmoides, Glycyrrhiza uralensis, Fritillaria cirrhosa, Fritillaria thunbergii, Astragalus membranaceus var. mongholicus, Asarum heterotropoides var. mandshuricum, Schisandra chinensis, Platycodon grandiflorum, Pinellia ternata, Polygonum multiflorum, Macrocarpium officinale, Dendrobium nobile, Gynostemma pentaphyllum, Saposhnikovia divaricata, Gentiana manshurica, Salvia miltiorrhiza, Anemarrhena asphodeloides, Bupleurum chinense, Corydalis turtschaninovii f. yanhusuo, Crocus sativus, Belamcanda chinensis and Cimicifuga foetida.
Concurrently with these developments in the cultivation of Chinese medicinal plants, many exotic medicinal plants have been introduced and brought under cultivation. About 30 introduced species have successfully been grown during the past 30 years. The main among these are as follows: Eugenia aromatica, Scaphium lychnophorum, Amomum compactum, Strychnos wallichiana, Styrax tonkinensis, Silybum marianum, Panax quinquefolium, Atropa belladonna and Digitalis lanata.
Active research is being carried out on various aspects of cultivation and processing of a wide range of medicinal plants. Examples include: rapid propagation of Siraitia grosvenorii and Aloe vera var. chinensis; the use of fermentation technology for the processing of Cordyceps sinensis, Ganoderma lucidum and Armillaria mellea; tissue culture for the production of active principles of Panax ginseng, Panax notoginseng, Ligusticum chuanxiong, Glycyrrhiza uralensis, Panax quinquefolium, Lithospermum erythrorrhizon, Hyoscyamus niger, Corydalis turtschaninovii f. yanhusuo; and imporoving cultural practices for higher yields and better quality of Eucommia ulmoides, Coptis chinensis, Magnolia officinalis, Lonicera japonica and Tripterygium wilfordii. (NABCMD, 1989; Peng and Xiao, 1993).
In addition to the species under cultivation, approximately 2,000 species of exotic medicinal plants are currently maintained in Chinese botanical gardens.
A. lancea is an example of species of which the natural population size has decreased seriously as as a result of overcollection. In semi-cultivated species, the loss of genetic variability occurs very rapidly and can reach serious levels even in the absence of any significant decrease in the total number of individuals. The conservation of a medicinal plant species with a wide range of genetic diversity is therefore even more difficult than that of rare and endangered species with a small number of individuals. As cultivation has a very strong influence on the erosion of genetic variability, for many semi-cultivated medicinal plants, in spite of the apparent stability in their total population size, conservation measures are required as urgently as for rare and endangered species.
Although A. lancea is widely distributed in central China, the traditional, high quality medicinal material called Mao-Cangzhu comes from the Maoshan mountains. This plant is mainly used for the treatment of indigestion and stomach disorders. The highest recorded production of this crude drug in Jiangsu province was 6.6 tons per year. But in 1983 the annual production was only 1.2 tons. Based on the production figures for A. lancea in five counties of Jiangsu province, viz. Juroug, Jintan, Lishui, Liyang and Gaochun, the highest production was recorded in the 1950s. The figures for the 1980s were much lower than those for the 1960s and 1970s. Resources of A. lancea were seriously being depleted in all five counties in Jiangsu. The data indicate a sharp reduction in deposits as soon as commercial collecting activities began. The existing resources would only last for 10-20 years if no steps are taken towards conservation. The slow growth rate of the species is an important reason for such a rapid depletion. Experiments to measure growth rates have shown that the rhizome grows only to twice its original size in any given year. Protection and cultivaiton are therefore absolutely essential for A. lancea (He et al., 1993).
Determination of genetic variation
A knowledge of genetic variation is essential for conservation purposes as well as for selecting the appropriate planting material to use in agronomic work aimed at improving production under cultivation.
Although the Maoshan area is the famous region for the Cangzhu variety of A. lancea, the species is distributed over a wide area including Jiangsu, Zhejiang, Shandong, Anhui, Hubei and Sichuan provinces. Based on the data for Jiangsu, Anhui and Hubei provinces, it grows at altitudes from 60 to 1,000 m above mean sea level. The sites investigated have a relatively similar climatic pattern, except for precipitation which varied between sites from 850 to 1,560 mm per year. Soils are mostly acidic, about pH 5, and occasionally alkaline, pH 7.5, The rocks are mostly granite and quartzite, but also limestone in places. High density distributions of Cangzhu A. lancea are usually found only on the north facing slopes.
Morphological differences have been observed between plants growing
under different ecological conditions. For verifying the morphological
differences which are genuinely due to genetic factors, plant samples were
collected and cultivated in the Nanjing Botanical Garden experimental plots.
Collections from various designated sites were propagated vegetatively.
Plants of different provenances had different leaf shapes (Fig.1) and it
has been confirmed that these are due to real genetic variation among them.
Figure 1: Leaf shapes of Atractylodes lancea according to different provenances in China
Morphological information alone is not sufficient for making decisions concerning the choice of appropriate provenances for conservation or cultivation. For these purposes, it is also essential to know the active principle content of the plant material. Analyses of the major active constituents of A. lancea showed that not only plants growing in different geographic areas with different morphological characteristics could have different chemical constituents but also plants with similar morphological features and growing on the same site may have different contents of chemical constituents. For example, analyses carried out on 144 samples collected from four sites in Jiangsu province with similar morphological features indicated that there were at least two variations with respect to the presence or absence of various chemical constituents (Table 1).
Table 1. Variations in chemical composition of Atractylodes lancea
|Variation||Number of samples||Percentage of total population||Presence (+) or absence (-) of constituents|
|Others||44||30||Outside the above types|
For conservation we may obtain specimens exhibiting different characteristics including morphological and chemical variations, and keep them in the collection. But for the choice of material for cultivation, more studies need to be carried out on the clinical effectiveness of the different provenances, especially based on their chemical composition. This kind of research usually takes a relatively long time. This example illustrates the complexity of the various issues involved in the conservation and cultivation of medicinal plants.
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