Studies on the Cultivation and Uses of
Evening Primrose (Oenothera spp.) in China
Yu-Cheng Deng, Hui-Ming Hua, Jun Li, Peter Lapinskas
Economic Botany 55(1), p83-92.
Contents:

Abstracts
Origin and distribution in China
Early uses
The Commercial production in China
Development of evening primrose cultivation in China
The physicochemical constants of evening primrose oil
Oil processing technology and quality standards
Evening primrose oil as a medicine
Other research and applications relating to evening primrose oil in China
Conclusion
Literature cited

Abstracts

Yu-Cheng Deng, Hui-Ming Hua, Jun Li (Department of Plant Resources & Phytochemistry, Institute of Applied Ecology, Academia Sinica, PO Box 417, Shenyang 110015, Peoples Republic of China) and Peter Lapinskas (26 Deepdene Wood, Dorking, Surrey, RH5 4BQ, England). STUDIES ON THE CULTIVATION AND USES OF EVENING PRIMROSE (OENOTHERA SPP.) IN CHINA. Economic Botany 55(1):83-92, 2001. Evening primrose originated in North America and became naturalised in the North-East of China about one hundred years ago, where it has been used as famine food and animal feed. New uses for the seed oil, which contains g-linolenic acid (GLA), which have been developed in China and overseas since 1980 have created a much larger commercial demand for the seed. There are 8 species of Oenothera L. growing wild in China, of which Oenothera biennis L. is preferred. The maximum annual production of wild evening primrose seed is estimated to be about 3000 tonnes but, since 1986, evening primrose has also been cultivated for its seed and oil using O. biennis (primarily in the provinces of Jilin, Liaoning, Hebei and Shandong) in order to meet the increasing demand. New production techniques have been developed and disseminated, and reported seed yields range from 750 to 3000 kg ha-1. Commercial production follows a cyclical pattern, with the largest harvest to date, in 1999, estimated at 16-19,000 tonnes of seed.

During 20 years of research on a wide range of wild oilseed plants, Chinese scientists found that evening primrose oil was anti-atherosclerotic, lowered hyperlipidaemia and was antithrombotic. The oil was developed and licensed as a drug (which required work on processing technology, physicochemical characteristics, pharmacology, formulation and clinical studies) and it has since been widely used in clinical practice. Further research work has been done on other bioactive properties of evening primrose oil, alternative sources of GLA, the concentration of GLA, the synthesis of prostaglandin E1, and the development of health care drugs and cosmetics containing evening primrose oil. We believe that the prospects for the future development of evening primrose are good.

Chinese abstract

Key words: Evening primrose; Oenothera spp.; Cultivation; Oil; GLA; Medicine; hyperlipidaemia; China.

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Origin and distribution in china

Oenothera biennis L. originated in North America, and was introduced into China as a garden flower and as a weed before 1900, with the development of civilisation and communications with Western countries. It then become naturalised in the eastern mountain areas of three provinces (Heilongjiang, Jilin and Liaoning) of North-East China, and Shandong province. It grows on the plains, lower mountains and hilly areas at an elevation of 50 - 300 metres; on grassland, southern mountain slopes and wastelands; on the margins of fields, roads and forests; and in sparse woods. It grows best and can turn into the dominant species on sunny fields and fertile, damp soil (Deng, Gao and Li 1982; Deng, Hua and Duan 1993; Li, et al. 1994; Liu 1977; Zhu, Wu and Li 1989), but it will also grow on slightly saline or alkaline soil.

There are at least 8 species belonging to the genus of Oenothera L. which grow wild in China (Anonymous 1992a, 1992b; Deng 1988; Deng, Gao and Li 1982; Deng, Hua and Duan 1993; Duan 1990; Li, et al. 1994; Liu 1977; Liu, Wang and Shan 1983; Zhu, Wu and Li 1989). O. biennis is the dominant species, and it is highly variable, both in terms of subspecies and races. Other species found in the wild include O. glazioviana Micheli (syn. O. erythrosepala Borb. and O. lamarckiana de Vries), O. odorata Jacq., O. Oakesiana Gray, O. parviflora L., O. rosea Ait., O. stricta Ledeb. and O. villosa Thunb.

At present, it is the species O. biennis which is primarily used commercially. The seed oil contains an essential fatty acid, g-linolenic acid (GLA) which is not found in the normal diet, yet it is an essential intermediate in human metabolism. The oil is therefore extracted from the seed to make medicine, nutrients and health products in China and its seeds and oil are exported for use in pharmaceutical and healthfood products overseas.

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Early uses

O. biennis was introduced into China about a century ago. From then on, in famine years, local farmers living in the eastern mountain areas of the three provinces in North-East China gathered the tender roots and leaves of O. biennis as an edible wild vegetable, crushed its seeds with a stone roller and baked cakes (with wheat flour added), or squeezed oil from the seeds for use as a salad oil or drying oil (Anonymous 1960; Deng, Gao and Li 1982; Zhu, Wu and Li 1989). The decoction of its roots simmered in water has been used as a folk oral remedy for the common cold and for laryngitis (Anonymous 1992a, 1992b). Some local farmers used the whole plants as pig feed, and the seeds as bird and poultry feed. Some primary school students even gathered the seeds to exchange for pencils and paper.

In addition, an infusion of the roots of O. glazioviana soaked in wine has been used as an oral folk remedy for rheumatism and bone and muscle aches (Anonymous 1992a, 1992b).

However, over the last 20 years, evening primrose seeds have been produced on a much larger scale. Now they are mainly purchased by the rural native product corporations for export, and by local pharmaceutical and oil processing factories.

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Commercial production in China

China is now the major producer of evening primrose seed in the world, with an estimated 90% of total supply, which it has been able to achieve through the combination of low-cost hand labour, and growing conditions which are ideally suited to the crop. Commercial production began with seed harvested from the wild (primarily O. biennis) for export as 'wild sesame' in the 1970's (Fedeli, Paganuzzi and Tiscornia 1976), with the first shipments for healthfood use leaving in 1980. The maximum annual production level for wild seed, of about 3,000 tonnes, was reached in 1985, so cultivation as a crop (using wild-collected seed) began in 1986 to meet the escalating demand which resulted from the launch of a Chinese medicine for lowering hyperlipidaemia and the continuing growth of demand in export markets where the oil was sold as a health food supplement. For example, by 1988, in Yanbian area of Jilin Province, it was planted on about 2,000 ha., and the output of seeds was about 2,000 tonnes. Although global demand for the oil has been reasonably consistent, and growing, since 1985, the supply (and hence the price) has fluctuated dramatically. This is primarily because, although there is some contracted production, there are also a large number of speculative crops sown by individual small farmers. Because they have no knowledge of the world market situation, they tend to base their planting decision on the price obtained for the previous year's harvest. Thus, when seed is short and prices high, too many farmers sow the crop, driving the market into surplus the following year, forcing down prices to uneconomic levels. As a result, most of them drop out, leading to a shortage the year after, and the cycle begins again. In fact, because of the possibility of biennial crops, and various market factors, the peak-to-peak cycle time seems to be about 5-7 years. Thus there were market surpluses from the harvests in 1986, 1991 and 1992, and 1999, and corresponding shortfalls in between.

In terms of volume, in the production peak of 1992, in Liaoning and Jilin Province, the output of seeds was about 10,000 tonnes (Wu, et al. 1994), and in Shandong Province, evening primroses were planted on 430 ha. from which 500 tonnes of seeds were produced (Li, et al. 1994), yet the export market was estimated to require only around 2,500 - 5,000 tonnes (J. X. Tang, personal communication) and the domestic market 800 - 2400 tonnes of seed equivalent (assuming an average of 8 tonnes of seed for 1 tonne of oil).

The surplus from the 1999 harvest has been particularly severe as it followed two years of shortage (and hence very high prices) because of a large number of climate-induced crop failures. Current export demand is usually estimated to be running at 1000-1200 tonnes of oil per year (8000 - 9500 tonnes seed-equivalent) and the total yield in 1999 is generally estimated to have been double this. (Hard data on yields is not available because of the fragmented and secretive nature of the market.)

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Development of evening primrose cultivation in China

The rapid increase in demand for evening primrose seed up to 1986 resulted in severe seed shortages and high market prices which aroused the interest of many institutes and farms who began to research and disseminate the methods of cultivation and breeding of evening primrose.

The following description of the main techniques and points for attention is a summary of the practice in the five provinces of Jilin, Liaoning, Hebei, Shandong and Jiangsu (located at north latitude between 32° and 45°, and at east longitude between 115° and 130°) (Anonymous 1992c; Deng, Hua and Duan 1993; Duan 1990; Li, et al. 1994; Liu, Wang and Shan 1983; Sun 1990; Wu, et al. 1994; Yu 1982; Zhang 1994; Yu and Tian 2000).

Life Cycle:

Evening primrose is sown between 15th March and 15th April. Polyethylene sheeting is used in some areas to warm the soil. The seedlings emerge after 6 to 13 days. In areas of lower temperature, the seeds are sown in a greenhouse, and the resulting seedlings are transplanted. They flower from June to September. The capsules ripen from the middle of August through to the first ten days of October. The reproductive cycle is about 125 days in Jilin, 150 days in Hebei, 180 to 200 days in Shandong. The height of the plants normally varies from 1.0 to 1.5 metres but can reach 1.75 metres. Plants which are sown after the middle of May mostly become rosettes (literal translation 'lotus throne') and neither bolt nor flower during that year. Biennial evening primrose is sown between July and September, is cut down by the frost over winter, and starts to regrow from the root crown in the following March, ripening in September.

Persistence:

The evening primrose which has formed the shape of lotus throne (rosette) by Autumn can survive through the winter even with temperatures as low as -22°C. It has strong resistance to drought, diseases and insect pests. On the other hand, wet and hot conditions in the rainy (summer)season, long-term accumulation of water and over-crowded plants may bring about root rot, leaf blight and loss of leaves. Sometimes, insect pests appear, such as Agrotis ypsilon, Acherontia lachesis, Cryptothelea pryeri, Ectomyclois ceratoniae and Gryllotalpa unispina. (Zhang 1994).

Cultural Technique:

The soil is carefully prepared and fertiliser (farmyard manure and/or chemical fertiliser) applied. The row spacing used is in the range 33 - 60 cm, the drill being irrigated before sowing and the seed covered with soil to the depth of 0.4-0.5 cm, pressed slightly and irrigated again if necessary. The sowing rate used is between 3.0 and 9.5 kg ha-1. The average weight of a thousand seeds is 0.373 g (0.236 - 0.535 g), and the optimum germination percentage is 80 - 98%. Before sowing, the seeds are normally soaked in water at 40°-50°C for 24-48 hours, or put into oven at 25°C to hasten germination (Li, et al. 1994). In North-East China the seed may be vernalised by soaking it in water or mixing it with wet soil and then burying it in the frozen soil in early spring (Anonymous 1992c; Zhu, Wu and Li 1989). In some areas, the seed is sown into frozen ground in the Autumn, so that it can become fully vernalised over winter in situ to give an early germination and establishment the following spring. The crop is weeded 2 to 4 times during the growing season by hand hoeing. The plants are thinned and finally singled 2 to 3 times in June to give a density of 75,000 plants per hectare in Shandong (Li, et al. 1994), 210,000 in Liaoning (Anonymous 1992c), and 300,000 in Jilin (Wu, et al. 1994). Densities which are too high result in over-tall crops with weak stems which are prone to disease and lodging. The fields are irrigated if necessary. The plants are gathered when two-thirds of capsules have become ripe, and stacked in sheaves for threshing. After threshing (by hand, or mechanically using animal drawn sledges or wheeled vehicles) the seed is dried in the sun, and stored in a dry well-ventilated warehouse, free from mice, and sheltered from the sun. The yield of seeds is generally between 1125 and 1530 kg ha-1, and in some better situations, may reach 1,875 kg ha-1 in Beijing (Duan 1990) and up to 2,700 kg ha-1 in Jilin (Anonymous 1992c; Wu, et al. 1994). In 1992, the yield reached 3,000 kg ha-1 in the experimental fields in Qingyuan County. In 1993, in the experimental field of 0.15 hectare in Rizhao City of Shandong Province, an even greater yield, equivalent to 3,750 kg ha-1 of seeds, was recorded (Zhang 1994).

In Shandong Province, evening primrose is either inter-cropped with peanuts, soybeans, medicinal herbs or saplings, or grown on sandy wastelands (Li, et al. 1994; Zhang 1994).

Experiments on the cultivation of O. biennis have also been carried out in Jilin City of Jilin Province and Dongtai City of Jiangsu Province in order to extract a volatile oil and a concentrated solvent-extract (gum) from plant tissues (Li, et al. 1994; Sun 1990).

Cultivation of the evening primrose crop not only provides raw material for the medical industry and export trade, but also contributes to a diversified economy in the countryside, the increase of economic income, the conservation of water and soil and the beautification of the environment. In the future, further research is needed for the production of improved varieties with more flowers and a higher yield of seeds (Anonymous 1992c; Duan 1990; Wu, et al. 1994; Zhang 1994; Zhao and Wu 1993; Zhao, et al. 1994), higher content of seed oil and GLA (the GLA of some varieties has reached 12.0%) (Duan 1990), and a more consistent maturation period. In addition, some research is needed on the photoperiodic response for bolting (Zhao and Wu 1993) and on tissue culture (Gu 1989).

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The physicochemical constants of evening primrose oil

As an example, the following figures were obtained on oil processed from the seeds of wild O. biennis collected in Fengcheng County of Liaoning Province. The percentage of oil in the seeds was 26.4%. The oil was deep yellow, with a refractive index (20°C) of 1.4770, specific gravity (20°C) of 0.9310, iodine value of 139.7, saponification value of 188.2, acid value of 2.8, aceto value of 24.9, thiocyanogen value of 83.9, and unsaponifiable matter of 1.1%. The fatty acid composition of the oil (expressed as the percentage of total fatty acids) was reported as 0.8 caprylic acid, 0.4 capric acid, trace lauric acid, 0.4 myristic acid, 6.1 palmitic acid, 1.8 stearic acid, trace arachidic acid, trace behenic acid, 7.7 oleic acid, 73.4 linoleic acid, 9.2 g-linolenic acid (Deng 1987, 1988; Zhu, et al. 1980).

The oil percentage and the composition of the main fatty acids in seeds of 8 species of evening primrose grown in Beijing are shown in the following table (Deng 1988; Deng, Hua and Duan 1993; Duan 1990).

TABLE 1. The oil percentage and the composition of the main fatty acids (% of total fatty acid methyl esters) in seeds of 8 species of evening primrose grown in Beijing (Duan 1990).



Oil and Fatty Acid(%)
 
Species Oil
percentage
in seed
Palmitic
acid
16:0
Stearic
acid
18:0
Oleic acid
18:1 (9c)
Linoleic
acid
18:2 (9c, 12c)
GLA
18:3
(6c, 9c, 12c)

19 samples of
O. biennis growing
wild in Liaoning
and Jilin provinces
 
19.0-30.1 5.0-6.7 1.1-2.9 4.7-10.7 73.5-81.9 6.8-9.4
O. biennis
 
24.7 5.97 1.52 11.16 73.13 8.20
O. erythrosepala
 
17.4 7.45 1.64 6.58 75.48 8.85
O. glazioviana
 
19.9 5.31 1.36 12.93 73.19 7.18
O. lamarckiana
 
7.0 7.89 1.62 5.94 75.26 9.32
O. odorata
 
24.4 10.76 2.42 6.46 76.93 3.30
O. parviflora
 
26.6 4.79 3.06 13.54 67.92 10.15
O. rosea
 
13.4 8.97 1.58 6.33 83.11 trace
O. villosa
 
23.9
6.21 1.90 6.82 76.03 9.02

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Oil processing technology and quality standards

There are at least 10 factories producing evening primrose oil from seed in China. In 1986, the oil factory of the Institute of Applied Ecology, Academia Sinica (IAE), formerly known as the Institute of Forestry and Soil Science, Academia Sinica, began to extract the oil with mechanical screw presses using the following process (Deng, Hua and Duan 1993). The seeds are winnowed to remove foreign substances. The seed skins are softened using steam and the oil extracted without additional heat using a spiral oil press. After filtering, the oil is refined by neutralising with alkali, deodorising with steam, and decolouring by charcoal filtration. It is then dried, and filtered again to give the final product. Vitamin E is added to the oil. The oil is poured into drums which are purged with nitrogen, sealed and stored under refrigeration. In China, oil is also extracted by means of solvent (normally hexane) and, to a small extent, with supercritical CO2 (Yu, et al. 1992).

The refined evening primrose oil produced by IAE is pale yellow and transparent, with a moisture content of less than 0.2%. Its specific gravity (25°C) is 0.915 - 0.935. The acid value is typically 0.3 mg KOH per gram of oil (the standard set by the Chinese pharmaceutical administration is below 2.5), the peroxide value is 0.03% (the standard is below 0.15%). The GLA percentage averages 9.1% (the standard is above 7.0%). There are no organic solvent residues, arsenic, cadmium, lead, mercury or residues of agricultural insecticides. The content of GLA is determined with gas chromatography (Anonymous 1987; Deng, Hua and Duan 1993). Product specifications for the content of GLA vary between suppliers; 10%, 9 - 10%, and 8 - 9% are all quoted.

Over the last five years, several joint-ventures with experienced foreign partners have been established in China for the local extraction and processing of evening primrose oil. It is likely that this injection of capital and expertise will further improve the quality of the oil.

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Evening primrose oil as a medicine

Evening primrose seed oil has been widely studied in the West since the 1970's as a potential treatment for a large number of medical conditions, including eczema, mastalgia, diabetic neuropathy, cancer, multiple sclerosis, rheumatoid arthritis and elevated blood cholesterol levels. Pharmaceutical licences for products containing evening primrose oil for the treatment of eczema and mastalgia have been granted in the United Kingdom and several other countries. The work performed in the West is well known and has been substantially reviewed elsewhere (Horrobin 1990a, 1990b, 1992, 1994 and 2000; Huang and Mills 1996; Fan and Chapkin 1998).

The work performed in China during this period is, however, less well known in the West, as it has been largely published in Mandarin. In fact, thorough studies on evening primrose oil and GLA started independently in China in 1980, as described below.

Researchers in the Department of Phytochemistry of the IAE began a study into the oil chemistry and possible applications of wild oil plants in 1962 (Deng 1982, 1987, 1988; Li, et al. 1983; Zhu, et al. 1980). After completing the determination of fatty acids in the seed oils of 350 plant species, they engaged mainly in research on the wild plant O. biennis, from 1981 to 1985. The areas covered included: its availability as a raw material (Deng, Gao and Li 1982; Deng, Hua and Duan 1993; Liu 1977; Zhu, Wu and Li 1989); pharmacognosy studies (Gao, Xu and Deng 1983); the separation and identification of g-linolenic acid (Gao, et al. 1982); the determination of fatty acids of seed oil from different species and areas; the technology of extracting, processing and refining the oil (Deng, Hua and Duan 1993); the formulation of a quality standard and tests of stability for the oil (Deng, Hua and Duan 1993; Wang, Zhu and Li 1989; Zhu and Li 1988); studies on the formulation as a drug; the pharmacodynamics of the oil (including its action in atherosclerosis; lowering triglyceride, cholesterol and a-lipoprotein; and reducing liver lipoidosis) (Wang and Xu 1984); toxicity testing (acute and subacute tests); mutagenicity (tests of accumulative toxicity, Ames, marrow cellular and micronuclei); and teratological effects (test of sperm malformation) (Deng 1988; Deng, Hua and Duan 1993).

Preliminary clinical observations began in 1982 on 88 patients with hyperlipidaemia. From 1984 to 1985, the formal clinical observation of 425 cases of this disease were carried out in the Shenyang Military Region General Hospital of the Peoples Liberation Army (Tong, Jiang and Zhou 1988), Liaoning Province Hospital, Beijing Tiantan Hospital, the First Subsidiary Hospital of Beijing Medical University and Beijing Friendship Hospital (Deng 1988). Patients were selected for the study on the basis of having two or more of the following blood indices above normal levels: cholesterol; triglyceride; low-density lipoprotein; high-density lipoprotein. All patients had blood cholesterol levels greater than 5.2 mmol per litre. The patients were randomised to the active and placebo groups The active group of 350 patients took soft-gelatine capsules containing four grams of evening primrose oil daily, the control group of 75 patients took 200 mg vitamin E daily, both for 90 days, and the parameters were measured at the end of the treatment phase and again 30 days later. Patients in the active group were aware that they were taking the experimental substance. There was no change in the diet or exercise treatment for either group. The results are shown in table 2. In addition, 57% of the subjects on the active treatment lost between 2 and 8 kg in body weight with no signs that this might be attributable to toxicity; there was no overall weight loss in the placebo group.

TABLE 2. The effect of evening primrose oil on hyperlipidaemia. The figures in the placebo and active column refer to the percentage of patients for whom the improvement in the measured parameter has exceeded the level given in the criteria column. T represents the time (90 days) at which treatment was stopped (Deng 1988).


 

Time of
measurement

Criteria

Placebo
(Vitamin E)
(n = 75)
 

Active
(EPO)
(n=350)

Probability
(c2)

Serum cholesterol (reduce)

T
T + 30 days
 

10%

39.8%
35.7%

68.2%
63.8%

<0.001
<0.001
Serum triglycerides (reduce) T
T + 30 days
 
15% 17.9%
40.8%
64.5%
81.5%
<0.001
<0.001
Low density lipoprotein (reduce) T
T + 30 days
 
10% 31.4%
33.3%
58.4%
64.8%
<0.001
<0.001
High density lipoprotein (raise) T
T + 30 days
 
10% 50.0%
75.0%
63.5%
74.5%
N.S.
N.S.

In the spring of 1986, this drug (Capsulae Oenotherae Biennis Olei, Soft Capsules of Evening Primrose Oil) was appraised and approved by the Western Medicine Branch of Liaoning Province Drug Evaluation Committee as a new medicine (Category 2). The quality standards of the medicine and the corresponding oil have been adopted by the medicine administration departments in other areas of China. The research project on this drug was awarded the second prize of Liaoning Province Science and Technology Advancement in 1988. More than 20 factories have put it into production including at least 9 registered pharmaceutical factories (Deng 1988; Deng and Wei 1986; Ma 1985). They mainly use the Type II soft capsule making machines made by the Spaceflight Ministry of China, with good performance. The IAE oil factory has generated substantial funds for research work through the manufacturing and sale of the oil. They also sell an enriched evening primrose oil with 25% GLA. At present, the Department of Phytochemistry is engaging in research on soft capsules of evening primrose oil (Hua, et al. 1994) in combination with other compounds.

The research workers of Bethune University of Medical Sciences in Changchun City also worked on research into the use of GLA in evening primrose oil as a medicine (g-Evening Primrose-E Soft Capsule) from 1984 to 1985. Their work included biochemical experiments on the inhibition of aggregation of platelets and the synthesis of TXA2 by platelets (Fu, Wu and Gu 1987). The clinical observation of 228 cases in which each subject took 1.2 - 2.7 grams of oil daily was carried out. The drug was approved in Jilin in 1985 and put on the market. This project won second prize for Science and Technological Advancement from the Chinese Ministry of Public Health in 1987. There were therefore two independently developed licensed drugs using evening primrose oil available in China by 1986, although it was not until 1988 that an equivalent product (Epogam, developed by Scotia Pharmaceuticals Ltd for the treatment of eczema) was licensed in a Western country. Since 1989, the Shenyang College of Pharmacy together with others, has developed an oil emulsion product (Yao and Ren 1987; Yu, et al. 1986). This was introduced as a medicinal product ('Evening Primrose Oil Emulsion') in 1991 in Chongqing City of Sichuan Province, and increased the range of indications to include diabetes and pre-menstrual syndrome.

GLA in evening primrose oil has also been studied in treating inflammatory diseases (Sun, et al. 1986), lowering blood lipids (Guo, et al. 1987; Shi, Liu and Shi 1990), reducing body weight in obesity (Du and Wang 1988) and treating nephrosis (Liu 1994).

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Other research and applications relating to evening primrose oil in China

Alternative sources of GLA

There are about 10 families of higher plants containing GLA of which Onagraceae, Boraginaceae and Saxifragaceae have some potential for use. The oil containing GLA from the seeds of Ribes species is used as health care medicine in Harbin City and Changchun City. The researchers of Plant Resource Department of IAE studied the relationship between GLA in 13 species plants of currants (Ribes) and their plant taxa. The Tree Physiology Department of IAE investigated the cultivation of borage (Borago officinalis L.) which yielded about 375 kg ha-1 of seed containing 34% oil, of which 22% (expressed as a proportion of total fatty acids) was GLA.

GLA also exists in some species of alga, fungus, bryophyte and pteridophyte. In 1987, the Shanghai Institute of Industrial Microbiology acquired a strain of Mucorales which contains 7-9% GLA (Lin and Zhang 1994). In 1989, the Microbiology Department of IAE screened the C8761 and T8765 strains containing 12 - 18% and 22 - 24% GLA respectively (Zhao, et al. 1991).

Concentration of GLA

Workers at the Beijing Teachers University extracted the principal GLA-containing triglyceride (containing one-third GLA) from evening primrose oil to produce a 90.9% pure triglyceride oil by freeze crystallisation. The concentration of GLA was thereby raised by a factor of 4-5 fold (Xiao and Yan 1986). GLA contents of up to 80% were achieved in a hydrolysed mixture of free fatty acids by one inclusion of the urea adduct method (Song and Hong 1988). GLA methyl esters can be further purified up to 98% by AgNO3 column chromatography (Song and Hong 1990).

Semi-synthesis of PGE1

In 1982, the Phytochemistry Department of IAE proposed that PGE1 could be prepared from the substrate g-linolenic acid in evening primrose seed oil through dihomo-gamma-linolenic acid with sheep seminal vesicle enzyme (Liu, Zhu and Cai 1975; Struijk, et al. 1966). This research was carried out together with Shenyang Pharmaceutical University (SPU), and Bethune University of Medical Sciences in 1983 (Chen, Hong and Gao 1986; Deng 1988; Gu, et al 1985). The pharmaceutical factory of SPU has put the method into production in small batches.

Commercial development of evening primrose oil products in China

There are at least 10 different types of products in which evening primrose oil is the main component which are sold in China, in the nutritional, medical, anti-obesity and cosmetic markets. Products containing evening primrose oil have been licensed for sale for medicinal purposes in the following regions: Hebei, Jiangsu, Zhejiang, Fujian, Guangxi, Jiangxi, Hubei, Guizhou, Sichuan, Xinjiang and Inner Mongolia. The products are made in pharmaceutical factories, institutes or pharmaceutical colleges in a range of locations, including Changchun, Shenyang, Beijing and Shanghai City. Other components which are added to the evening primrose oil include soybean phospholipids, flavonoids, vitamins, trace elements and amino acids. The seed oil of Perilla frutescens (L.) Britt. is also used as main component of combination health products. This oil contains 51.1 - 63.8% of alpha-linolenic acid which belongs to w-3 family of fatty acids (Deng 1987). Some products include fish oil containing EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid) (Deng, Hua and Li 1998; Wang 1995). These products can take many forms, including capsules, emulsions, poultices and creams.

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Conclusion

We believe that evening primrose oil and GLA have an important role to play in human nutrition, health care and cosmetics, and especially in relation to a variety of common diseases, which are otherwise difficult and complicated to treat. In addition, commercial development in this area could lead to important social and economic benefits, so we hope that this work will be continued both in China and overseas (Deng, Hua and Li 1995; Deng et al. 1998; Horrobin 1995; Wang 1995; Zhang and Xiao 1997).

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Literature cited

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Note: The references above are in English, unless noted otherwise. Some of these papers are hard to obtain in the West; the number which appears after some of the articles is my internal reference number, and indicates that I have a personal copy of that article.

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