- Taxus canadensis
Taxobox
name = "Taxus canadensis"
image_width = 200px
status = LR/lc | status_system = IUCN2.3
regnum =Plant ae
divisio =Pinophyta
classis = Pinopsida
ordo =Pinales
familia =Taxaceae
genus = "Taxus "
species = "T. canadensis"
binomial = "Taxus canadensis"
binomial_authority = Marshall"Taxus canadensis" (Canadian Yew) is a conifer native to central and eastern
North America , thriving in swampy woods, ravines, riverbanks and on lake shores. Locally called simply "Yew", this species is also referred to as American Yew or Ground-hemlock. Most of its range is well north of theOhio River . The southernmost colony known is in theRed River Gorge inKentucky .It is usually a sprawling
shrub , rarely exceeding 2.5 m tall. It sometimes forms strong upright central leaders, but these cannot be formed from spreading branches, only from the original leader of the seedling plant. The shrub has thin scaly brownbark . The leaves are lanceolate, flat, dark green, 1-2.5 cm long and 1.5 mm broad, arranged in two flat rows either side of the.The seed cones are highly modified, each cone containing a single
seed partly surrounded by a modified scale which develops into a soft, bright redberry -like structure called anaril , open at the end. The seeds are eaten by thrushes,waxwing s and otherbird s, which disperse the hard seeds undamaged in their droppings. The male cones are globose, 3 mm diameter. It is a monoecious plant – one of the few in the genus.Uses and traditions
While one would be ill-advised to consume this plant, it is nonetheless thought to be of lower toxicity than "
Taxus baccata ". All parts of the plant, save the aril, should be considered toxic.Tribes in its native range used small quantities of yew leaf tea topically or internally for a variety of ailments – notably
rheumatism . Tribes are also been said to have used yew twigs in steam baths to help alleviaterheumatism . Again, it should be noted that the plant is still quite toxic and modern herbalists prefer safer, more effective herbs."Taxus canadensis" is also being harvested in northern
Ontario ,Québec andAtlantic Canada as the plant is a source of the class of poisonous chemicals known astaxane s, which have been a focus forcancer research. "T. canadensis" is much more abundant than the near-threatened "Taxus brevifolia " (Pacific Yew), and the "greens" (new growth) can be harvested sustainably every five years, instead of stripping the bark and killing the plant.The most abundant taxane in "T. canadensis" is 9-dihydro-13-acetylbaccatin III, which can be effectively converted to
10-deacetylbaccatin III , used in the production ofpaclitaxel . Recently, two new taxanes have been identified from "T. canadensis", including 7β,10β,13α-triacetoxy-5α-(3'-dimethylamino-3'-phenylpropanoyl)oxy-2α-hydroxy-2(3→20)abeotaxa-4(20),11-dien-9-one and 2α,10β-diacetoxy-9α-hydroxy-5α-(3'-dimethylamino-3'-phenylpropanoyl)oxy-3,11-cyclotax-4(20)-en-13-one.References
*
* Gunawardana, G. P. "et al." (1992). [http://cat.inist.fr/?aModele=afficheN&cpsidt=4458772 Isolation of 9-dihydro-13-acetylbaccatin III from Taxus canadensis] . "J. Nat. Prod." 55 (11): 1686-1689.
* Nikolakakis, A. "et al." (2000). [http://cat.inist.fr/?aModele=afficheN&cpsidt=1396732 Taxus canadensis abundant taxane : Conversion to paclitaxel and rearrangements] . "Bioorg. Med. Chem." 8 (6): 1269-1280.
* Shi, Q. W. "et al." (2006). [http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=pubmed&cmd=Retrieve&dopt=AbstractPlus&list_uids=16556995&query_hl=7&itool=pubmed_docsum Two new alkaloidal taxoids from the needles and sap of "Taxus canadensis"] . "Biosci. Biotechnol. Biochem." 70 (3): 732-6
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