L’If Canadian : composition des boutures versus les plantes matures.

Petzke, Tracy L. (2002). L’If Canadian : composition des boutures versus les plantes matures. Mémoire. Québec, Université du Québec, Institut National de la Recherche Scientifique, Maîtrise en sciences expérimentales de la santé, 124 p.

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Résumé

The isolation of paclitaxel (Taxol®, Bristol-Meyers Squibb) in 1971 by Wani et al. and the eventual approval of it's use as a treatment for breast, ovarian and lung cancer almost twenty years later has greatly increased the study of paclitaxel and it's analogues, the taxanes. There are over three hundred and fifty of these natural products already reported from various natural sources, largely from the many species of yew, each with varying structural characteristics and bioactivities. The taxanes are studied not only for their potential anti-cancerous properties but also for the information they may provide towards the elucidation of the biosynthetic pathway of paclitaxel. The study of the Canadian Yew, Taxus canadensis, has shown that this species of yew differs from the other species of yew not only its appearance, which is smaller and rambling, but also in its composition of taxanes. While major taxanes such as paclitaxel and 10-deacetyl-baccatin III found in the numerous other species ofyew are also found in the Canadian Yew, their proportions are different. Also different is the taxane 9-dihydro- 13-acetyl-baccatin III, which has been reported as the major taxane of the Canadian Yew. Found only in minute quantities in other species ofyew, this taxane is found in quantities three to seven times greater than the amount of paclitaxel in the Canadian Yew, regardless of the season ofyear or location of the plant (Zamir et al., 1995:73:655). This difference in the composition of the Canadian Yew versus the other species of yew has spurred the continued study of the Canadian Yew in the laboratory of Dr Lolita Zamir. ln this study, the taxane content of rooted cuttings of Taxus canadensis was assessed and compared to the content of the previously studied needles and stems of the mature Taxus canadensis plant. The study of the composition ofrooted cuttings was done in order to establish whether a difference in composition between the mature Canadian yew and its rooted cuttings existed, and to thereby lead to the possible establishment of rooted cuttings as a feasible model for future biosynthetic studies, as weil as to possibly lead to the discovery of new taxanes. Twenty-nine taxanes were isolated and characterized from the rooted cuttings of Taxus canadensis by a series of chromatography purifications, using column chromatography and high-pressure liquid chromatography (HPLC) techniques. The resulting purified taxanes or mixtures of taxanes were analysed by NMR and mass spectroscopy. These analyses allowed the characterization of three new taxanes as weil as the identification of twenty-six known taxanes, of which fourteen taxanes were isolated for the first time from Taxus canadensis. The three major taxanes isolated from the rooted cuttings were 5-decinnamoyl-taxagifine, 10-deacetyl-baccatin III and paclitaxel, compared to 9-dihydro-13-acetylbaccatin III, taxinine and taxinine E as already reported for the mature Canadian yew (Zamir et al., 1992:33:36:5173, Zamir et al., 1995:73:655). These results show a difference in the taxane content of the rooted cuttings versus the mature Taxus canadensis and suggest a change in the taxane content of the plant may be due to the preparation of the rooted cuttings from the mature trees. The previously reported difference in taxane content of the Canadian yew compared to the other yew species, combined with the difference in taxane content of the rooted cuttings compared to the mature Canadian Yew encourages the continued study of the rooted cuttings of the Canadian Yew in our laboratory. This may lead to the possible future use ofthese plants as models for biosynthetic studies ofpaclitaxel in the Canadian yew.

Type de document:	Thèse Mémoire
Directeur de mémoire/thèse:	Zamir, Lolita
Mots-clés libres:	if-canadien ; paclitaxel
Centre:	Centre INRS-Institut Armand Frappier
Date de dépôt:	10 sept. 2014 13:56
Dernière modification:	16 sept. 2015 16:20
URI:	https://espace.inrs.ca/id/eprint/2343

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