t. brevifolia 2
TRANSCRIPT
Taxus brevifolia
Ben Merritt
-Biology, Chemistry, and Pharmacology
Taxus (Taxaceae)- Evergreen trees or shrubs; not resinous
or aromatic
Roots – fibrous, woody
Leaves – needles, persist for several years (evergreen), spirally arranged
(alternate), resin canals may be present or absent
Bark – scaly or fissured
-6-10 species --- mostly unique
because of geographical
location
Taxus Growth Forms
T. chinensis
T. bacata“Repandens”
T. bacata“Little Gem”
T. brevifolia var. reptaneta
Taxus
Seeds – one per “cone,” surrounded by fleshy aril Pollen Cones – produced annually,
axillary, globose/ovoid
- Reproductive Structures
Seed Cones – 1-2 ovules, axillary
T. cuspidata
- Aril is edible but seeds are toxic
T. brevifolia Anatomy-shrub/small
tree 15-25m tall (200y to mature)
-dioecious
-bark scaly; outer scales
purplish/brown
-branches horizontal/droo
ping
-vegetative reproduction
common
-inner scales reddish/purple
-leaves 1-2cm x 1-4mm
-epidermal cells mostly taller
than wide
-seeds mature late
summer/fall
Habitat
-Western NA – Alaska south to Montana, Idaho and
California- Lives in moist
areas around river banks, ravines
-Sea-level to 2200m
-May grow in sun or shade
(needs acclimation
period)
Common Names
The only common names seem to be “Pacific Yew” and
“Western Yew.” - “yōl’-kō” in
Concow language (CA)
Latin Name
Taxus brevifolia (Nutt.)
brevi - = short, abbreviated
-folia = foliage; leaves
↵1. Loanword of Scythian (Iranian) origin; means simply “yew” in Latin
2. From the Greek, meaning “bow”; origin of word “toxic”
Traditional Uses
-Was sometimes used in Native American
(Algonquin) smoking mixtures called
kinnikinnick
-Needles of Taxus with uva-ursi plant said to
produce “too strong of an effect”
-Wood was used by Native
American tribes to make bows
-Used similarly by the ancient
Greeks/Romans –
considered toxic
Modern Uses
-Originally found to have cytotoxic effects on cancer cells (antineoplastic) -Less toxic than other species, most taxol Used on a variety of
cancers (breast, ovarian, lung, colon, leukemia)
-Often 24-h infusion every few weeks
Parts used
Primarily the bark and leaves (active
constituents in phloem)
-Was initially tested against KB cells (HeLa
derivatives); have carcinoma and
papilloma cancersOrder of potency (extract)
stem > bark > root > needles > wood >twigs
-Needles first require non-polar wash to
remove fats (then CO2, or other)
T. cuspidata
Constituents
- Taxol – Isolated first in 1966 by Wall and Wani (0.02%, dried bark)
Contains variety of Taxanes –
taxol most active
Mechanism of Action
Microtubule (MT) stabilization
-Beta-tubulin binding only
-Promotes assembly, discourages depolymerization
-Prevents mitosis, eventual cell death
Undesirable Effects of Taxol Administration
(Long-term)
Causes build-up of MT’s
Effects rapidly-dividing cells – gut, bone marrow, lymphocytes
-Hypersensitivity (allergic reaction)
-Mostly due to vehicle (cremophor) – some use albumin -Peripheral Neuropathy (doses greater than 170mg/m2) – also may result from cremophor
-Neutropaenia
-Problems with heart (arrythmia, bradycardia)
-Vomiting-Mucositis (dig., painful)-Dysphagia
Isolation/SynthesisFrom the bark (0.01-0.02%):
MeOH, then methylene chloride/H20 (or chloroform)
From the needles (0.025-0.044%):
Hexane pre-wash (waxes, lipids)
- [ ] in bark rises over summer- Concentration increases in plant material after letting sit for a week or two
Hauser Chemical used 15,000lb of bark for 1kg of taxol (0.015%)
Semi-synthetic route (80%)
10-deacetlybaccatin IIITotal synthesis
possible
Other Methods of Isolation
Plant Cell Fermentation: Grow Taxus calluses in aqueous media, extract taxol (chromatography, crystallization)-Bristol-Myers Squibb
Endophytic Fungi?-Taxomyces andreanae
Original study – (1993)-15-20% of taxanes is taxol-24-50ng/liter-May require precursors
Later study – (2013)-Not found to have homologous genes/evidence of trans-kingdom gene transfer
- Thought to remain in membrane after isolation from tree!!!
The Future
Taxol and related taxanes are useful in the treatment of cancer, but they have many terrible side effects.
Further research should be centered around:
1. Molecules with less toxic effects2. Specific cell targeting (work is being done with IG)3. Better vehicles for administration (albumin, pro-drug)
• ATCC. “KB (ATCC® CCL-17TM).” <http://www.atcc.org/products/all/CCL-17.aspx> May 1 2014. • EPA. “Greener Synthetic Pathways Award: Bristol-Myers Squibb Company.”
<http://www2.epa.gov/green-chemistry/2004-greener-synthetic-pathways-award> Last updated 16 March 2014. • Hagiwara, H. and Y. Sunada. “Mechanism of Taxane Neurotoxicity.” Breast Cancer. Vol. 11(1): pp. 82-5. 2004. • Heinig, U., S. Scholz, and S. Jennewein. “Getting to the Bottom of Taxol Biosynthesis by Fungi.” Fungal Diversity. Vol. 60:
pp. 161-170. 9 April 2013. • Itokawa, H. and Kuo-Hsiung Lee. Taxus: The Genus Taxus. New York: Taylor and Francis, 2003. eBook. • Lowe, J., H. Li, K.H. Downing, and E. Nogales. “Refined Structure of αβ-Tubulin at 3.5 Å Resolution.” Journal of Molecular
Biology. Vol. 313(5): pp. 1045-57. 9 November 2001. • Markman, M. “Taxol: An Important New Drug in the Management of Epithelial Ovarian Cancer.” The Yale Journal of
Biology and Medicine. Vol. 64: pp. 583-90. 26 March 1991. • Mitchell, A.K. “Acclimation of the Pacific Yew (Taxus brevifolia) Foliage to Sun and Shade.” Tree Physiology. Vol. 18: pp.
749-57. 1998. • Morin, N. R. Flora of North America: Volume 2: Pteridophytes and Gymnosperms. Edited by Flora of North America
Editorial Committee. Toronto: Oxford University Press, 1993. eBook. • Sarosy, G., and E. Reed. “Taxol Dose Intensification and Its Clinical Implications.” Journal of the National Medical
Association. Vol. 85(6): pp. 427-31. 1993. • Stierle, A, G. Stobel, and D. Stierle. “Taxol and Taxane Production by Taxomyces andreanae, an Endophytic Fungus of
Pacific Yew.” Science. Vol. 260: pp. 214-216. 9 April 1993. • Suffness, M. Taxol Science and Applications. Boca Raton: CRC Press LLC, 1995. eBook.