Undercover federal agents. Illegal sourcing of drug supplies. An endangered species pushed to the brink of extinction.
Not crystal meth today (the endangered species is a bit of a giveaway), but some of the the results of the discovery that certain rare species of Yew trees contain extracts that inhibit cancer cell growth.
Luckily, those aren’t the only results. Millions of patients with cancer have been treated with the drug since it was licensed in 1993.
This project starter includes information and practical protocols to help you investigate the medical effects of plant extracts, by looking in detail at the inhibitory effects of conifer extracts on plant and microbial growth.
Get inside the science
There are two chemotherapy drugs that were originally developed from Yew trees. The first to be discovered, paclitaxel (Taxol), was made from the bark of the Pacific yew tree. The second, docetaxel (Taxotere), was first made from the needles of the European yew tree.
It is well known that conifer trees, such as Yew trees, contain compounds which inhibit the growth of other plants. Conifer trees tend to have few other species of plants growing under them and experiments can be done which show that pine needles have an inhibitory effect on the germination of seeds such as cress.
In the 1960s, the US National Cancer Institute carried out a major programme to discover new anti-cancer drugs in plants. Researchers went out into different environments, gathering plant samples and sending them back to the lab. Here, the lab scientists discovered that the extracts of Pacific yew bark showed cytotoxic activity. This began a long process of research and investigation, to discover what the active components were, and then to translate it into a clinical drug. (See the link below for the history of Taxol development.)
Taxol affects structures within the cell called microtubules, ‘freezing’ them in place, and preventing them from separating the chromosomes when a cell divides. This kills dividing cells, and has a particular effect on rapidly-dividing cancer cells.
Unfortunately, the discovery that these – and other, now critically endangered species of Yew – had medicinal properties, led to illegal logging which may still be taking place.
More recently, it has also been reported that extracts from the immature cones of a species of common conifer tree (Lawson’s Cypress) contain anti-bacterial agents which may be effective against MRSA.
You can carry out a number of practical investigations yourself to research the inhibitory effects of conifer extracts on plant and microbial growth.
Find out more
- The history of Taxol development How this cancer drug was developed
- How bark from the Pacific yew tree improved the treatment of breast cancer. (The Pharmaceutical Journal, 21 September 2011, from the Royal Pharmaceutical Society)
- Why don’t we prescribe bark for cancer? A doctor introduces the pharmacology and toxicology of plant-derived drugs
- Yew – symbol of death and life A brief introduction to the history of the medical effects of yew trees. (The Pharmaceutical Journal, 26 February 2009, from the Royal Pharmaceutical Society)
- How does Taxol work? A news story from University of California Berkeley, reporting on the discoveries of UC Berkeley scientists into how the drug works. Includes a video and animation showing its effect on microtubules.
- Antibacterials and modulators of bacterial resistance from the immature cones of Chamaecyparis lawsoniana, Smith et al (Phytochemistry 68 (2007) 210-217) This research article covers Eileen Smith’s work on antibacterials from Cypress cones. If you look around the site, you’ll find other articles by Eileen Smith that may also give you useful research ideas.
Practical Investigations – step-by-step protocols
We’ve put together step-by-step protocols for you to use for a practical investigation on this topic.