As most elementary school science worksheets explain (complete with bolded vocabulary terms and the same tired examples offered when you were in elementary school), trees are a renewable resource that provide humans with the raw materials for making finished goods like lumber, paper and pencils.
The thrust of the lesson is true enough, but it sells trees short. Take the examples of finished goods; while lumber and paper are certainly important for modern civilization, trees have yielded products that are arguably even more important: medications.
From pain killing bark extracts to cancer-killing compounds, trees produce a number of important tools that are helpful in the fight against suffering and disease.
Oh, My Aching Bark
The primary active ingredient in aspirin is derived from the bark of willow trees. Although first produced in its modern form by Bayer in 1899, humans have used willow bark extracts for pain relief since 400 B.C.
The bark itself is a popular herbal remedy for a variety of ailments, including back pain, inflammation and toothaches. The amount of salicylic acid — the active ingredient in the willow bark – varies from one species to the next. White (Salix alba), purple (Salix purpurea) and crack willows (Salix fragilis) are among the species with the highest proportion of the salicylic acid, and they are most commonly used to manufacture aspirin.
Some birch trees (Betula ssp.) also contain salicylic acid, although they are not used the commercial manufacture of the drug. However, folk remedies commonly encourage the chewing of birch twigs to relieve pain.
Some trees are important allies in the fight against cancer. In 1962, researchers working at Research Triangle Institute’s Natural Product Laboratory in Research Triangle Park, NC, found that extracts from the bark of Pacific yews (Taxus brevifolia) exhibited cytotoxic (cell-killing) characteristics in laboratory tests.
Eventually, researchers identified the active chemical from the bark, called paclitaxel. By 1977, paclitaxel had demonstrated anti-tumor activity in mice. Unfortunately, paclitaxel was difficult to synthesize at the time; but after developing a way to extract the precursor to paclitaxel from the bark of the common yew (Taxus baccata) – which is very common – production began to ramp up.
To date, the National Cancer Institute states that, Taxol (the proprietary name for the drug) is the “best-selling cancer drug ever manufactured.” (National Cancer Institute)
Native to the Western United States and Canada, the cascara tree (Rhamnus purshiana) has been an important medicinal tree for hundreds of years. Often called the Cascara Sagrada (“sacred bark” in Spanish), the tree produces compounds – known to chemists as hydroxyanthracene glycosides – that work as natural laxatives.
Scientists continue to learn new things about the cascara tree and the medical benefits it may offer. For instance, some evidence has suggested that another compound in the bark – emodin – may exhibit both cancer- and virus-fighting abilities. (Dang Shuangsuo, 2006) (Gopal Srinivas, 2003)
One of the most important diseases in the history of Homo sapiens, malaria is a deadly parasite that continues to threaten those living in tropical locations. While often produced synthetically, quinine is a very old malaria medication, which is derived from the bark of several trees of the genus Cinchona.
During the Civil War, quinine was a difficult substance to obtain. In response, doctors of the time turned to a common North American species: the flowering dogwood (Cornus floridana), whose bark also produces antimalarial compounds.
Dang Shuangsuo, Z. Z. (2006). Inhibition of the replication of hepatitis B virus in vitro by emodin. Medical Science Monitor.
Gopal Srinivas, R. J. (2003). Emodin induces apoptosis of human cervical cancer cells through poly(ADP-ribose) polymerase cleavage and activation of caspase-9. European Journal of Pharmacology.
National Cancer Institute. (n.d.). Success Story: Taxol® (NSC 125973). Retrieved from U.S. National Institutes of Health: http://dtp.nci.nih.gov/timeline/flash/success_stories/S2_taxol.htm