Taxus cuspidata
Scientific classification Edit this classification
Kingdom: Plantae
Clade: Tracheophytes
Clade: Gymnospermae
Division: Pinophyta
Class: Pinopsida
Order: Cupressales
Family: Taxaceae
Genus: Taxus
Species:
T. cuspidata
Binomial name
Taxus cuspidata

Taxus cuspidata, the Japanese yew[2] or spreading yew, is a member of the genus Taxus, native to Japan, Korea, northeast China and the extreme southeast of Russia.

It is an evergreen tree or large shrub growing to 10–18 m tall, with a trunk up to 60 cm diameter. The leaves are lanceolate, flat, dark green, 1–3 cm long and 2–3 mm broad, arranged spirally on the stem, but with the leaf bases twisted to align the leaves in two flattish rows either side of the stem except on erect leading shoots where the spiral arrangement is more obvious.

The seed cones are highly modified, each cone containing a single seed 4–8 mm long partly surrounded by a modified scale which develops into a soft, bright red berry-like structure called an aril, 8–12 mm long and wide and open at the end. The arils are mature 6–9 months after pollination. Individual trees from Sikhote-Alin are known to have been 1,000 years old.[3]

Uses

It is widely grown in eastern Asia and eastern North America as an ornamental plant.

Toxicity

The molecular structure of taxine B
The structure of Taxine B, the cardiotoxic chemical in the yew plant

The entire yew bush, except the aril (the red flesh of the berry covering the seed), is toxic due to a group of chemicals called taxine alkaloids. Their cardiotoxicity is well known and act via calcium and sodium channel antagonism, causing an increase in cytoplasmic calcium currents of the myocardial cells. The seeds contains the highest concentrations of these alkaloids.[4][5] If any leaves or seeds of the plant are ingested, urgent medical advice is recommended, as well as observation for at least 6 hours after the point of ingestion.[6][7] The most cardiotoxic taxine is Taxine B followed by Taxine A; Taxine B also happens to be the most common alkaloid in the Taxus species.[5][8][9] Yew poisonings are relatively common in both domestic and wild animals who consume the plant accidentally.[10][11][12] The taxine alkaloids are absorbed quickly from the intestine and in high enough quantities can cause death due to general cardiac failure, cardiac arrest, or respiratory failure.[13] Taxines are also absorbed efficiently via the skin and Taxus species should thus be handled with care and preferably with gloves.[14] Taxus baccata leaves contain approximately 5 mg of taxines per 1g of leaves.[8] The estimated (i.e. not by any means a fact) lethal dose (LDmin) of Taxus baccata leaves is 3.0-6.5 mg/kg body weight for humans[15] There is currently no known antidotes for yew poisoning, but drugs such as atropine have been used to treat the symptoms.[16] Taxine remains in the plant all year, with maximal concentrations appearing during the winter. Dried yew plant material retains its toxicity for several months and even increases its toxicity as the water is removed,[17] fallen leaves are also toxic.[18] Although poisoning usually occurs when leaves of yew trees are eaten, in at least one case a victim inhaled sawdust from a yew tree.[19]

The following book made it clear that it is very difficult to measure taxine alkaloids and that this is a major reason as to why different studies show different results.[20] Minimum lethal dose, oral LDmin for many different animals were tested:

  • Chicken 82.5 mg/kg
  • Cow 10.0 mg/kg
  • Dog 11.5 mg/kg
  • Goat 60.0 mg/kg
  • Horse 1.0–2.0 mg/kg
  • Pig 3.5 mg/kg
  • Sheep 12.5 mg/kg

Several studies[21] have found taxine LD50 values under 20 mg/kg in mice and rats.

For symptoms of human toxicity see Taxine alkaloids

Male and monoecious yews in this genus release toxic pollen, which can cause the mild symptoms see Taxine alkaloids. The pollen are also a trigger for asthma. These pollen grains are only 15 microns in size, and can easily pass through most window screens.[22]

References

  1. ↑ Katsuki, T.; Luscombe, D (2013). "Taxus cuspidata". IUCN Red List of Threatened Species. 2013: e.T42549A2987373. doi:10.2305/IUCN.UK.2013-1.RLTS.T42549A2987373.en. Retrieved 19 November 2021.
  2. ↑ USDA, NRCS (n.d.). "Taxus cuspidata". The PLANTS Database (plants.usda.gov). Greensboro, North Carolina: National Plant Data Team. Retrieved 8 December 2015.
  3. ↑ "Памятник природы "Сихотэ - Алинь". Центр реабилитации диких животных "УТЕС"" [The nature monument "Sikhote - Alin". Center for the rehabilitation of wild animals "UTES"]. Туристические комплексы[Tourist complexes] (in Russian). Archived from the original on 2007-09-29.
  4. ↑ Garland, Tam; Barr, A. Catherine (1998). Toxic plants and other natural toxicants. International Symposium on Poisonous Plants (5th : 1997 : Texas). Wallingford, England: CAB International. ISBN 0851992633. OCLC 39013798.
  5. 1 2 Alloatti, G.; Penna, C.; Levi, R.C.; Gallo, M.P.; Appendino, G.; Fenoglio, I. (1996). "Effects of yew alkaloids and related compounds on guinea-pig isolated perfused heart and papillary muscle". Life Sciences. 58 (10): 845–854. doi:10.1016/0024-3205(96)00018-5. PMID 8602118.
  6. ↑ "TOXBASE - National Poisons Information Service".
  7. ↑ "Plants for a Future Taxus baccata". Retrieved 2019-07-17.
  8. 1 2 Smythies, J.R.; Benington, F.; Morin, R.D.; Al-Zahid, G.; Schoepfle, G. (1975). "The action of the alkaloids from yew (Taxus baccata) on the action potential in the Xenopus medullated axon". Experientia. 31 (3): 337–338. doi:10.1007/bf01922572. PMID 1116544. S2CID 8927297.
  9. ↑ Wilson, Christina R.; Sauer, John-Michael; Hooser, Stephen B. (2001). "Taxines: a review of the mechanism and toxicity of yew (Taxus spp.) alkaloids". Toxicon. 39 (2–3): 175–185. doi:10.1016/s0041-0101(00)00146-x. PMID 10978734.
  10. ↑ "JAPANESE YEW PLANT POISONING - USA: (IDAHO) PRONGHORN ANTELOPE". ProMED-mail. 24 January 2016. Retrieved 25 January 2016.
  11. ↑ "PLANT POISONING, CERVID - USA: (ALASKA) ORNAMENTAL TREE, MOOSE". ProMED-mail. 22 February 2011. Retrieved 25 January 2016.
  12. ↑ Tiwary, Asheesh K.; Puschner, Birgit; Kinde, Hailu; Tor, Elizabeth R. (May 2005). "Diagnosis of Taxus (yew) poisoning in a horse". Journal of Veterinary Diagnostic Investigation. 17 (3): 252–255>. doi:10.1177/104063870501700307. PMID 15945382.
  13. ↑ Fuller, Thomas C.; McClintock, Elizabeth M. (1986). Poisonous plants of California. Berkeley: University of California Press. ISBN 0520055683. OCLC 13009854.
  14. ↑ Mitchell, A. F. (1972). Conifers in the British Isles. Forestry Commission Booklet 33.
  15. ↑ Watt, J.M.; Breyer-Brandwijk, M.G. (1962). Taxaceae. In The Medicinal and Poisonous Plants of Southern and Eastern Africa. Edinburgh, UK: Livingston. pp. 1019–1022.
  16. ↑ Wilson, Christina R.; Hooser, Stephen B. (2018). Veterinary Toxicology. Elsevier. pp. 947–954. doi:10.1016/b978-0-12-811410-0.00066-0. ISBN 9780128114100.
  17. ↑ "Yew". Provet. Retrieved 23 March 2013.
  18. ↑ "Intoxicación por tejo".
  19. ↑ José Luis Hernández Hernández; Fernando Quijano Terán; Jesús González Macías (2010). "Intoxicación por tejo". Medicina Clínica. 135 (12): 575–576. doi:10.1016/j.medcli.2009.06.036. PMID 19819481.
  20. ↑ Clarke, E.G.C.; Clarke, M.L. (1988). Veterinary Toxicology: Poisonous plants, Taxaceae (3rd ed.). London: Baillière, Tindall & Cassell. pp. 276–277.
  21. ↑ TAXINE - National Library of Medicine HSDB Database, section "Animal Toxicity Studies"
  22. ↑ "Pollen images in size order". www.saps.org.uk. Retrieved 2017-04-13.
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