2.3.3 Taxol
Synonym Paclitaxel; Taxol A; NSC – 125973.
Biological Source It is obtained from the bark of the Pacific Yew tree, Taxus brevifolia Nutt belonging to the family Taxaceae.
Geographical Source The plant is a native to the northwest United States. It is a small, not so growing evergreen tree.
Preparation Keeping in view the paucity of the drug it look quite sometime to isolate taxol and establish its chemical structure. The very complexity of its chemistry has more or less turned its total synthesis into a not so viable and feasible economic exercise. However, an attempt is being made to enhance its availability through the semisynthetic route whereby the taxol precursors are usually obtained by extraction from the needles of largely available species of Taxus.
Example The chemical component, 10-descetylbaccatin III, isolated from the needles of Taxus baccata Linn., may be conveniently converted to taxol via simple synthetic route.
Note: The needles, in comparison to the bark, may be harvested without causing any injury to the plant whatsoever, and thus provides a rather more easily renewable plant source for the drug.
Chemical Structure The chemical structure is provided below:
Characteristic Features Taxol has the following characteristic features, namely:
(a) It has a taxane ring system,
(b) It has a four membered octane ring
(c) An ester side chain at C-13 of the taxane ring is a prime requirement for taxol’s cytotoxic activity, and
(d) The presence of an accessible hydroxyl moiety at C-2 of the ester side chain renders an appreciable enhancement of the cytotoxic activity.
Uses
1. Taxol is primarily employed in the treatment and management of metastatic carcinoma of the ovarian glands after the failure of follow-up chemotherapy.
2. It is also used in the treatment of breast cancer usually after the observed failure of combination chemotherapy for metastatic disease.
3. Because of its hydrophobic nature the injectable concentrate of taxol formulation meant for
intravenous infusion is normally solubilized duly in polyoxyethylated caster oil. However, before
injection it should be appropriately diluted in normal saline or dextrose solution or combination thereof.
