In this record, Q is our questions,and A is their answer. The letters before "A", A, B, C represents for three seniors from Hande.
Q: We are interested in yew trees and its product taxol. Yew is a endangered plant and widely allocated in Yunan. So we’d like to learn something about the usage and protect conditions of them. First we are wondering where is the materials come from and how it was distributed. Do you use yew woods under rough machining?
B A: After 2005, our materials came from several resource:
- Cooperation with farmer households and companies in this province;
- We have our own plant bases in Yunnan. Since 2000, we have developed bases in Wenshan, Diqing and Dali.
- Last decade, we purchased materials outsides. Some companies are planting yew trees and conducting rough machining, like Lishui,Zhejiang, Hongdou corporation in Jiangsu and so on.
- Import from Canada and Europe. But it’s only a little.
Q: Is the growth cycle too long to cause some problems?
B A: We can harvest just two years after planting. For it’s suitable for yew growth, their growth speed is sufficient. The appropriate growth condition of yew is elevation between 2000 m to 3500 m in acidic humus and pH between 5~7, shady environment. When it grows up, whole plant can be used.
Q: How to find a balance between harvest and plant growth? You know, picking more branches and leaves will influence its growth.
C A: Both growth and harvest have their own standards. We only use bark and roots before, which need diameter more than 15 cm. that’s too difficult to find. Now we use tender branches and buds, and we can harvest every year. We developed a technique that we add a kind of fungi or its spora, which were separated from soil near the root of wild yew tree, around the roots of young yew seeding, and that shows a improvement to yew growth.
B A: There are two kinds of harvest pattern. One is whole tree exploit and the other one is like picking tea. It’s a kind of recycle. For a kind of small yew in Sichuan, people exploit their whole trees, but harvest pieces of field a year and harvest other pieces next year. The whole tree exploiting occurred mainly on chinensis var.mairei, whose taxol mainly distributed in roots.
Q: We learned that you have two methods to produce taxol. One is half-synthesis and the other is extracting from the natural materials. And we have learned how are the two methods going. So what do you think is the advantage of the two ways respectively? Which one is better to the company?
A A: It depends on the costumers who will pay attention to the curation. The drugs will take activity examination. And costumers would choose products based on the examination. Company prefers to use half-synthesis for it is easier than extracting.
C A: If you test both taxol from natural and synthesis, there would be a little difference. The activity of the natural taxol will be little higher. So half-synthesis product is cheaper. When we synthesis taxol, we get some byproduct which can be machined chemically to agents with similar curation. And the impurity of natural taxol and synthesized taxol is different, in both variety and quantity.
The half-synthesis takes 9 days for a batch, and produce 4-5 kilos taxol, but natural way needs 50 or so days and 2 kilos a batch. And both methods will generate many by product which can also make profits. We prefer to chemically synthesize. But people usually prefer nature medicine. So natural way takes larger ratio. And we also need to improve quality of our synthesized taxol
Q: Have you thought about some improvement about these techniques? What about PCF (Plant Cell Fermentation™)
A: We haven’t thought about this question. This tech is not mature now and the cost of fermentation is very high. The impurities of this tech is too much to discard and there is no clear standard about it. There are some new method to produce taxol but we will do experiments only after sufficient assessment about them. Maybe when someday it becomes clearer, we ‘ll think about it.
Q: Now there are many companies in China synthesizing taxol, so which do you think gave you more pressure, domestic or abroad?
A: Mainly come from abroad. We faced more on global market. In the late 1970s, American started to extract taxol from natural materials. In 1990s, European extract 10-DAB from Taxus baccata, and 10-DAB can easily chemically synthesize to taxol. These technology are very mature in Japan, India, Czech, Netherland, and the most pressure comes from the restrict supervision and quality control in other countries.
Q: How many times is a yew tree harvested a year? How long can it be used? And is it true that we can just harvest afer two years and take profits every year?
A: It’s a complex question. We can harvest after we plant trees 2 years. They accumulate biome between March to October and people harvest in autumn and winter, that is from September to November in Yunnan. For small plant we harvest every twice years, and for larger plants people can harvest every year. The profits to plant yew is relative with yew’s environment. Generally if the natural material have taxol less than 0.01% or the CAD less than 0.05%, then they are waste. Sometimes farmers plant trees with no guide and no plans, as a consequence, they suffered great loss. What’s more, the yew tree are mainly planted on crop field. Then this kind of disaster had great effect to society and economy. So it’s very important to unite company and farmers.