Chapter 1.9

1.9 - Yew family - taxus canadensis

Charlee Anderson , University of Guelph, Canada

Suggested citation for this chapter.

Anderson,C. (2022) Labrador tea. In The Student Encyclopedia of Canadian Indigenous Foods. Editor, M.N. Raizada, University of Guelph, Canada. http://www.firstnationsfoods.org/

Introduction

Taxus canadensis, known as Eastern yew, Ground Hemlock, or Taxus brevifolia, also known as the Western yew or Pacific yew, are different types of yew, that are all native to Canada. The yew can be found growing all over Canada and has been collected and used by many different groups of Indigenous peoples in several different ways. The purpose of this research section is to educate Canadians about the amazing properties of the yew plant, its history, and the different ways we can use this plant to benefit Canadian Indigenous peoples as well as anyone wanting to learn about yew plants today.

Morphology And Species Identification

Yews can be classified in different ways due to their growth patterns. The Eastern yew is described as one meter or smaller, straggling multi-branched shrub (Kuhnlein & Turner 1991), while the Western yew is typically a twisted and leaning small tree, usually five to ten meters. Although yews growth habits can differ, they all have commonalities between them. In a journal by Kuhnlein & Turner (1991) they describe the needles as 20mm thick and less than one inch long, typically they appear brownish green from above with a green underside and come to a pointed tip. The twigs are borne sightly, (contain or produce buds along itself for more branches), and they can appear flattened due to being 2-ranked (produce leaves directly across from each other in two vertical lines) as well, while the bark is scaly, with a reddish appearance. Kuhnlein & Turner (1991) also explain that the yew is a dioecious plant, meaning that one plant has only female flowers or only male flowers. The male produces small, yellowish pollen cones while the female produces berry-like fruits that are globular and pinkish red in color. The fruits of the yew ripen in late summer to early fall, on the underside of their twigs (Kuhnlein & Turner 1991).

Correct identification of this plant is necessary as it contains toxins that are harmful to humans if ingested (Kuhnlein & Turner 1991). For more information on the lethality of yews please see “Toxicity and Information”

Figure 1. images of the western yew tree located outside the university of Guelph. Image A shows a close view of the bark. Image B shows the shape of the leaves and berries.(Original Photos, 2022)

Toxicity And Information

Yews are an extremely toxic plant due to having diterpenoid alkaloids, such as Taxine A and B which can inhibit calcium and sodium transport in myocardial cells (Lee 1998). In the journal, by Kuhnlein & Turner (1991) It is strongly advised against consuming any part of the plant. Although yews are extremely toxic, the fleshy outer part of the fruit (not including the seeds) is the most edible part of the plant, which many indigenous peoples consumed (Kuhnlein & Turner 1991).

If you suspect someone has consumed any part of the yew plant, call emergency services immediately. In a study reviewed by Hermes-Laufer et al. (2020), they stated in one case that it only took approximately 50-100g of needles to have a lethal effect, toxic impacts can occur as quickly as five hours after consumption and can result in loss of consciousness and risk cardiovascular arrest. The symptoms of yew poisoning range from mild gastrointestinal symptoms such as nausea and vomiting, to seizures, loss of consciousness, cardiac dysrhythmias, and cardiogenic shock (Hermes-Laufer et al. 2020).

Geographic Origins And Locations Today

Yews can grow as small trees or shrubs depending on their location. In a journal by Kuhnlein & Turner (1991), it is said Eastern Yews are typically small shrubs (see morphology and species identification) and commonly found growing in thickets or rich woods (figure 2). They originate and are located from south to Iowa and Virginia, southeastern Manitoba, and the Maritimes. Western Yews are typically small trees (see morphology and species identification) found within moist woods, around a low to moderate elevation, originating from coastal British Columbia to the north of the Alaska Panhandle southwest Alberta, as well as south to California, and can still be found there today (Kuhnlein & Turner 1991). The yew has become a popular ornamental shrub and isn’t propagated for much else currently, but you can find yews all over the world in gardens and yards due to it being an attractive bushy shrub that is easily shaped for outdoor decoration (Piesch & Wheeler 1992).

Figure 2. northern shrub thicket, photo taken by: Joshua G. Conhen, (Michigan Natural Features Inventory, 2022)

Indigenous Peoples Associations

Due to the yew being so widespread, many Indigenous communities used the plant in a variety of ways. The main groups that were found to have used the yew plant historically were the Masset Haida, Mendocino County Indians, Iroquois, Micmac, Potawatomi, and the Straits Salish peoples (Kuhnlein & Turner 1991). Not all these groups used the yew plant in the same way, as the yew was used both medicinally and for consumption. For more information on how different indigenous groups used the yew plant see the section on “Historical and Cultural Uses”.

Figure 3. Canadian Indigenous groups and their locations.(Native American Tribes Map: Indigenous Peoples USA, 2022)

Historical And Cultural Uses

In a Journal by Kuhnlein & Turner (1991), it was described that the outer part of the fruit (minus the seed) of the western yew was eaten in small quantities by the Masset Haida (figure 3) of the Queen Charlotte Islands and the Upper Lillooet of the interior of British Columbia, and by the Mendocino County Indians of California. The fruits as well as the leaves were brewed with maple sugar and water by the Iroquois (figure 3) of the Lake Ontario region to make a beer (Kuhnlein & Turner 1991). The Micmac of the Maritimes and the Forest Potawatomi (figure 3) used twigs of the eastern yew for brewing tea.) Some Washington Salish groups, and the Straits Salish (figure 3) used the leaves in “very potent” smoking mixtures (Kuhnlein & Turner 1991).

Medical Uses In The Treatment Of Cancers

Even though the yew plant seems to do more harm than good wherever it is grown, due to its toxic aspects (see “Toxicity and Information”), there is a few very good things that have come from this plant. In 1967, two compounds were found through isolation and synthesis from the bark of the Pacific yew (Taxus brevifolia), discovered by Monroe E. Wall and Mansukh C. Wani and his colleagues. (Priyadarshini & Aparajitha 2012). These compounds were paclitaxel (Priyadarshini & Aparajitha 2012) and synthesized docetaxel (Lyseng-Williamson & Fenton 2012).

In the review by Priyadarshini & Aparajitha (2012) Paclitaxel (figure 4) is described as a crystalline powder that is white to off-white in appearance, the trademark often referred to as Taxol. It is also said in the review by Priyadarshini & Aparajitha (2012) it was first isolated from the bark of Taxus brevifolia, it is a mitotic inhibitor drug that targets tubulin, but also stabilizes and protects microtubules against disassembly. Paclitaxel in various studies is shown as an effective anticancer agent against lung, breast, ovarian, leukopenia, and liver cancer (Priyadarshini & Aparajitha 2012). In the review by Lyseng-Williamson & Fenton (2012)

Docetaxel (figure 4) is often referred to as its trademark Taxotere, it is a cytotoxic taxane, that has an antimicrotubular agent effective in the treatment of metastatic breast cancer, that has failed previous rounds of chemotherapy. It is often thought to be similar to or even better than Paclitaxel at treating cancer but has more risks associated with neutropenia and other adverse events (Lyseng-Williamson & Fenton 2012).

Figure 4. differences in the molecular structures of Paclitaxel and Docetaxel. (Aamdal 2022)

Limitations – Toxic Boundaries Of Yews In Cultivation

Regarding the toxic nature of yews, farmers all over the world where species of the yew plant grow are wary of the toxic effect on livestock and must have been for many centuries, as the first description of yew poisoning in British literature was by Hurt in the Lancet and was written in 1836. (Lee 1998). The review by Parkinson (1996), discussed the sudden death of four horses on a small farm. It was reported that two of them were Morgan geldings and were seen eating just an hour prior to their death (Parkinson 1996). The post-mortem autopsy on one of the geldings reported finding needles of the yew plant in their digestive systems, containing the compound taxine, which causes cardiotoxic poisoning and cardiac arrest, resulting in the sudden death of these horses (Parkinson 1996). Horses aren’t the only livestock extremely susceptible to yew poisoning, cases of yew poisoning have been reported in goats, donkeys, sheep, and cattle as well (Ray & Binnington 1995). Death can occur within hours for livestock, in minutes after signs of ingestion of yews can be seen, such as trembling, depression, dyspnea, and collapse, but in most cases, livestock are simply found dead (Ray & Binnington 1995). From this information, it can be concluded that yews cannot be cultivated under any circumstances near livestock, and since the compound resists decomposition after storage and drying, even cuttings that have turned brown are still dangerous to consume (Ray & Binnington 1995). More information on the toxic properties of yews please see the section “Toxicity and Information”.

References

1.Kuhnlein H. V., Turner N. J. (1991). Yew Family (Taxaceae). Traditional Plant Foods of Canadian Indigenous Peoples Book Nutrition, Botany and Use, 8(3), pp. 44-45.

2.Lee M. R. (1998). THE YEW TREE (TAXUS BACCATA) IN MYTHOLOGY AND MEDICINE. Emeritus Professor, University of Edinburgh, 28(1), pp. 569-575. https://journals.sagepub.com/doi/pdf/10.1177/147827159802800414

3.Hermes-Laufer J., Meyer M., Rudiger A., Henze J., Enselmaan K., Kupferschmidt H., Muller D., Herzog A., Bettex D., Keller D. I., Kruger B., Engeler J. (2020). Extracorporeal life support as bridge to recovery in yew poisoning: case reports and literature review. ESC Heart Failure, 8(1), pp. 705-709. https://doi.org/10.1002/ehf2.12828

4.Piesch R. F., Wheeler N. C. (1992) INTENSIVE CULTIVATION OF TAXUS SPECIES FOR THE PRODUCTION OF TAXOL® -- Integrating Research and Production in a New Crop Plant. Weyerhaeuser Company & George R. Staebler Forest Resources Research Center. pp. 219-228. The original publication is available at:DOI: 10.17660/ActaHortic.1993.344.26

5.Priyadarshini, Aparajitha K. (2012). Paclitaxel Against Cancer: A Short Review. Medicinal chemistry, 2(7), pp. 139-141. DOI: 10.4172/2161-0444.1000130

6.Lyseng-Williamson K. A., Fenton C. (2012). Docetaxel – A Review of its Use in Metastatic Breast Cancer. Adis Drug Evaluation, 65, pp. 2513–2531. https://doi.org/10.2165/00003495-200565170-00007

7.Parkinson N. (1996). Yew poisoning in horses. The Canadian Veterinary Journal, 37(3), p. 68PMID: 8939338

8.Ray C. A., Binnington B. D. (1995). Yew poisoning in Sheep. The Canadian Veterinary Journal, 36(3), p. 446. PMID: 7585426

9.Native American Tribes Map: Indigenous Peoples USA. (2022). Wondering maps. https://wonderingmaps.com/native-american-tribes/

10.Michigan Natural Features Inventory. (2022). Michigan State University. https://mnfi.anr.msu.edu/communities/description/10677/northern-shrub-thicket

11.Aamdal S. (2022). High sensitivity assays for docetaxel and paclitaxel in plasma using solid- phase extraction and high-performance liquid chromatography with UV detection. ResearchGate. https://www.researchgate.net/figure/Molecular-structure-of-paclitaxel-and-docetaxel-Molecular-structure-of-paclitaxel-1a_fig1_7360513