The Origin and Source of Taxol

The Origin and Source of Taxol by Allen Meredith

Some observations and conclusions reached after years of study and research.
The original, written in 1997, has been edited for this article.

The Hampton Court Yews

The fact that several old yews at Hampton Court have been felled in recent years is a sad indictment that we appear to be more pre-occupied with formal garden design rather than seeing and appreciating the special presence of these 300 year old trees. They are after all trees which offer us a renewable source of a substance already of immense medicinal value, extracted chiefly from its evergreen needles. From this extract comes the ingredient called ‘taxol’. I would like to consider how I believe it might have even greater potential.

The use of taxol in drug form against certain kinds of cancer was, from its earliest trials, heralded as one of the biggest breakthroughs to date in the fight against cancer, because of the unique properties which it possesses, and the way these can be utilised to combat the disease. I believe that taxol/taxotere could be made to be even more effective than it is so long as more attention is paid to its point of origin, the yew tree.

We know that clippings from the Hampton Court Yews have already been used along with those from many other sources to help many hundreds of cancer patients. However it is my opinion that we need to be clear about the exact location of the batches of clipping that are used. At Hampton Court there are also avenues of yews, which are more important a source of origin than a yew hedge or maze. This is because yews in an avenue can be more readily identified as being female or male and, if it is not already becoming apparent in taxol research, it will become increasingly important to separate clippings into their gender origin. At present such attention is not given in the collection of clippings and if gathered from hedges or mazes, which are also to be found at Hampton Court, then the task of establishing gender is extremely difficult as both sexes of the yew grow so close to each other in such environments. Thus the yew avenue offers a better chance of gender selection at the outset and consequently vastly improves further research potential.

It is quite clear to me therefore that the chances of making future breakthroughs in Taxol research and treatment require the proper protection and registration of all yew avenues like Hampton Court.

Seasonal Variation Factors.

I have considered the need for the selection of yew needles by gender, for which a limited amount of work has already been done. This is also the case when considering how seasonal variation factors influence Taxol yields. (Griffin and Hook) It is surely time to look at the adequate funding of research possibilities which take into account the following criteria:

Examples:

Species - e.g. Taxus baccata

Gender - e.g. female

Estimated age - e.g. 300 years ( as in the case of Hampton Court ).

Month and season - e.g. late February, spring.

Conditions - e.g. wet or dry and if these conditions had been prevalent for some notable period previously, say three days at least, and especially if this was typically unseasonal.

Temperature - e.g. very cold, cold, mild, warm and hot and again note if these conditions had been prevalent for a noticeable period or were unusual.

Colour of needles - e.g. light green/dark green.

Specifically targeted methods of collection could also be used by for instance specifying spring collection from the male and summer for the female, thus they are gathered separately.

“The yew poison may be of moderate virulence only, and may occur in greater percentage in male than in female trees, or the percentage may vary from tree to tree without distinction of sex, and this may explain the capricious occurrence of poisoning……….also the half-dried leaves would be, ceteris paribus, more potent than the fresh. From an article “Variation in Taxol Content” by Professor Munro, published in the Journal of the Royal Agricultural Society 1892. Further details also in John Lowe’s The Yew Trees of Great Britain and Ireland.

We already know that there can be marked differences in taxol yield between sub species of the yew tree e.g. between taxus baccata and fastigiata, (Colin Morgan – Bedgebury Pinetum) but it is not yet so apparent that the yields are affected by seasonal and gender factors within each sub-species.

Furthermore it is becoming increasingly recognised that even individual yews might have unique chemical characteristics contained within the needle, aril, flower or trunk. After seeing thousands of Taxus baccata it becomes quite clear that the colour of the needles, the size of the berry, and the colour and character of trunk can all be quite different. These things may not appear to be so relevant now, but they could hold the minute difference between an extra year of life and a possible cure. Therefore during the course of any research we must respect and safeguard the future of this ‘Tree of Life’.

Identification - D.N.A. and ancestry

Very few areas of ancient yew wood remain anywhere in the world. Britain is the last main refuge for these trees. Therefore it is here that identification and tracking origins could be crucial. Most of the trees for example at Druid’s Grove or Newlands Corner may have originated from one or two trees - the parent trees. Natural layering by one or two yews could, over the centuries, create a wood or forest. A line of descent could be traced through DNA sampling to discover the ancestry of any yew. Hundreds of trees in the same forest might have shared the same D.N.A. in their wood for thousands of years. These origins might one day prove to be of importance in the development of life saving drugs.

Concentrations and strengths of yields are probably uppermost in the eyes of scientists but subtle differences in inherent qualities, as found in grape varieties for wine production, will probably reveal themselves to be of paramount importance. In looking more closely at the properties of the yew we should be prepared to consider all possibilities and rule none out at this point. We may have only taken the very first steps in recognising the potential of Taxol.

Planning for the Future.

I have tried to establish the importance of knowing as much detail as possible about the origin of the batches of needles used in research and to make taxol. If a particular yew, or group of yews, prove to have specific qualities that are beneficial then it is especially important to preserve those trees and preserve the line of descent through a planting programme taken from cuttings from individual trees.

The Conservation Foundation’s Millenium Yew planting programme which has taken cuttings from yews thought to be 2000 years old to eventually be placed in over 13000 parishes in Britain may be inadvertently activating one of the most important schemes of the new century as it will help to ensure the continuation of an ancient yew ancestry.

To safeguard our remaining especially ancient yews, we must not only protect them now but set up nurseries and plantations in areas where cuttings from the remaining yews can be maintained and propagated. The yews of ancient status which have survived this long should, it goes without saying, be protected by law.

There is no doubt that the yew contains a very powerful drug and we have to use it wisely and acknowledge where it comes from.

Additional notes :

Berries and seeds - how much attention has been paid to the healing qualities of the yew’s fruit, the red aril, and the seed therein rather than just the leaves and bark? Although very highly toxic, (indeed fatal if ingested) as the seed is, as well as the bark and leaves, the flesh of the surrounding fruit is not; but extreme caution is advised if the intention is to eat them, as the effects from consuming them can vary considerably from tree to tree, are not as yet properly understood and best avoided except under the most expert knowledge and supervision.

Fungi on the yew.

It would be an interesting exercise to examine the healing potential of the Yellow Sulphur Polypore, Laetiporus Sulphureus, as this is a very common fungus found on the yew, as well as the willow and the ash, which may well take on some of the properties of its host. Although sometimes cooked and eaten, second thoughts should perhaps be given to this intention if it is found growing on a yew. Its most potentially interesting stage however is when the bright yellow - orange stages of adolescent growth have paled as the fruit dries to an off-whitish colour. It is at this stage that it could be most potent concerning its medicinal properties. These dry brackets of this particular polypore could easily be reduced to powder form which investigative yew science may find to be of significant interest.

If amounts of Taxol are absorbed into the fungi, this may give an indicator in how to produce a soluble form of Taxol which could be directly administered to the patient. Probably natural quantities might not be suffcient but the equation of synthetic production might come in at this stage (see early reference to fungi in The Sacred Yew , p 234).

References :

Chetan A. & Brueton D. (1994) - The Sacred Yew, Penguin Arkana.
Griffin J. & Hook I. (1996 ) - Taxol Content of Irish Yews, PLANTA MEDICA, pp 370 - 372 Num62 .
Tabbush, P. & White, J. (1996 ) - Ancient Yew Woodand, Quarterly Journal of Forestry Vol 90 No.3 pp 197 - 206.

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