Editing Paclitaxel (section)

=== Bark processing ===
[[Image:Yew bark Taxol PD.jpg|thumbnail|The bark is peeled and processed to provide paclitaxel.]]

From 1967 to 1993, almost all paclitaxel produced was derived from bark of the Pacific yew, ''[[Taxus brevifolia]]'', the harvesting of which kills the tree in the process.<ref name="Gersmann 2011">{{cite news| vauthors = Gersmann H, Aldred J |title=Medicinal tree used in chemotherapy drug faces extinction|url=https://www.theguardian.com/environment/2011/nov/10/iucn-red-list-tree-chemotherapy|access-date=15 February 2017|work=The Guardian|date=10 November 2011|url-status=live|archive-url=https://web.archive.org/web/20170216143120/https://www.theguardian.com/environment/2011/nov/10/iucn-red-list-tree-chemotherapy|archive-date=16 February 2017}}</ref> The processes used were descendants of the original isolation method of [[Monroe Wall]] and [[Mansukh Wani]]; by 1987, the U.S. [[National Cancer Institute]] (NCI) had contracted Hauser Chemical Research of [[Boulder, Colorado]], to handle bark on the scale needed for [[Phases of clinical research|phase]] II and III trials.{{citation needed|date=June 2014}} While both the size of the wild population of the Pacific yew and the magnitude of the eventual demand for paclitaxel were uncertain, it was clear that an alternative, sustainable source of the [[natural product]] would be needed. Initial attempts to broaden its sourcing used needles from the tree, or material from other related ''[[Taxus]]'' species, including cultivated ones,{{citation needed|date=June 2014}} but these attempts were challenged by the relatively low and often highly variable yields obtained. Early in the 1990s, coincident with increased sensitivity to the ecology of the forests of the [[Pacific Northwest]], paclitaxel was extracted on a clinically useful scale from these sources.{{sfn|Goodman|Walsh|2001|pp=172–5}}