Regular or repeat readers of this here blog might recall a post I did around a year ago about the annual Autumn trimming of our Yew hedges. Well, it being October, we have obviously been doing much the same in the gardens at Chartwell once again this year but rather than go over old ground I thought I’d go into a bit more detail about one very important aspect of trimming yew trees and hedges: the use of the clippings for use in cancer treatments.
There are two chemotherapy drugs that were originally developed from Yew trees. One of them, docetaxel (Taxotere), was first made from the needles of the European yew tree. The other is called paclitaxel (Taxol) and was made from the bark of the Pacific yew tree. These chemical agents derived from the Yew are collectively known as taxanes. Both drugs can now be made semi-synthetically in the laboratory, but the needles are still collected and used as part of the process of making the drugs. The collecting season tends to be from July to the middle of September when the level of the active compound is greatest. Outside this time period the levels reduces significantly as the stems become woody.
This year, as in previous years we have collected our clean, fresh Yew clippings and had them collected by Chichester based company Limehurst, one of the country’s leading organisations in the harvesting and processing of medicinal plants. They have been harvesting Yew clippings for use in cancer treatments for over 20 years, collecting across England from over 4000 public and private gardens. This year we provided them with nearly 400kg of clipped Yew needles (390kg to be exact!) so we are very pleased to be ‘doing our bit’! For further information and to find out how to contact Limehurst, please visit their website at www.limehurst.co.uk
Once the clippings leave us there is much work to be done before they can be turned into cancer treatment drugs. After they are collected, the clippings are chopped finely and then put into large dryers to seal them before they are shipped to cancer treatment laboratories overseas. Once in the laboratory, the Taxane compound needed for use in cancer treatment is extracted under controlled conditions from this otherwise poisonous plant. The anti-cancer drugs produced from the yew clippings are then used to help patients with lung, ovarian, breast, neck and head cancer. The Taxane chemical was discovered in 1967 in a U.S. National Cancer Institute programme where over 200 plants were screened to identify their benefits.
And now the science bit! Taxanes present difficulties in formulation as medicines because they are poorly soluble in water. They are also difficult to synthesize because of their numerous chiral centres (an atom in a molecule that is bonded to four different chemical species – obviously!). Taxol, for example, has 11 of these tricky little atoms. The principal mechanism of action of the taxane class of drugs is the disruption of microtubule function. Microtubules are essential to cell division, and taxanes stabilize GDP-bound tubulin (globular proteins) in the microtubule, thereby inhibiting the process of cell division that cancer spreads by. Taxanes are essentially mitotic inhibitors. Taxanes are also thought to be radiosensitizing, which means they make tumor cells more sensitive to radiation therapy
It is not just big National Trust gardens like Chartwell that contribute to this important initiative. The Yew clippings from smaller private gardens are just as welcome at collection companies like Limehurst or Friendship Estates so there is no reason that you can’t get involved too.