Taxus Canadensis Research Articles

Modeling Canada yew (Taxus canadensis Marsh.) distribution and abundance in the boreal forest of northeastern Ontario, Canada

Canada yew (Taxus canadensis Marsh.) is a gymnosperm shrub that occurs in the understorey of coniferous and deciduous forests throughout the northeastern United States and southeastern Canada. Canada yew foliage contains high concentrations of paclitaxel and other taxanes, which have proven effective in treating many forms of cancer. A major challenge to the sustainable management of wild Canada yew harvest is the lack of a spatial inventory of the resource. The objective of this study was to develop a spatial model to predict the distribution and abundance of Canada yew populations in a forest landscape representative of the boreal forest region of Ontario, Canada. The study was conducted in the Romeo Mallete Forest (RMF) located on the southern edge of the boreal forest west of Timmins, Ontario. Abundance of Canada yew populations was assessed in 140 circular sample plots (5541m2), established at locations throughout the RMF. Canada yew abundance in each sample plot was estimated as the mean percent cover of three randomly located 100m2 subplots. Predictor variables were extracted from the Forest Resources Inventory (FRI) of the RMF, and from layers derived from remote sensing data covering the study area. A combination of classification and regression trees with Random Forests analysis was used to develop a classification model for FRI polygons based on patterns of Canada yew abundance, and assess the performance of the model. The classification error rate on the presence/absence model was approximately 21%, and the root mean squared error on the best continuous cover model was 9.1%. In all analyses, the most important classification node was based on percent basal area of the shade-tolerant late successional species Balsam Fir (Abies balsamea (L.) Mill), which suggests that patterns of Canada yew abundance are driven largely by time since disturbance.

Scale-Dependent Browsing Patterns on Canada Yew (Taxus canadensis) by White-Tailed Deer (Odocoileus virginianus)

Canada yew (Taxus canadensis) is a clonal shrub that forms discrete patches and was formerly an important component of forest understories in much of northeastern North America. Following Euro-American settlement, Canada yew has been extirpated or reduced in abundance throughout much of its former range, particularly in the USA; winter browsing by white-tailed deer (Odocoileus virginianus) has been implicated as responsible for much of its decline. Little is known about the factors affecting deer browsing intensity on Canada yew. We examined factors related to browsing intensity on Canada yew across three spatial scales in 29 forest stands in Michigan, USA. Browsing intensity on stems was related principally to two factors acting simultaneously across multiple spatial scales. Browsing intensity was negatively related to amount of Canada yew at the scale of the forest stand and negatively related to distance from the edge of Canada yew patches, effectively creating refugia from browsing. The browsing patterns we observed suggest that yew exists in two alternate stable states: (1) as loose aggregations of small stems or (2) large, dense patches of large stems. The implications of changes in deer density or snow cover to the probability of local persistence of Canada yew are discussed.

A new alkaloid taxane composed of two N-formyl rotamers from the rooted cuttings of Taxus canadensis

A taxane with an amino-side chain on C-5 was identified for the first time from rooted cuttings of the Canadian yew, Taxus canadensis. The structure was characterized as 2α,10β,13α-triacetoxy-5α-[3'-(N-formyl-Nmethylamino)-3'-phenylpropanoyloxy]taxa-4(20),12-dien-9α-ol (1) on the basis of 1D and 2D NMR data and HR-FAB-MS analyses. The spectra revealed that in CDCl3 solution 1 was composed of two rotamers (1a and 1b) in a ratio of approximately 1:1.

Resistance of Canada Yew (<em>Taxus canadensis</em>) Branch Wood to Two Wood Decay Fungi

Wood of the larger yews (Taxus spp.) is reported to be decay-resistant, but little is known about the decay resistance of Canada Yew (Taxus canadensis Marsh.) wood. Branch wood from Canada Yew was compared to branch wood from Northern Red Oak (Quercus rubra L.) and Eastern White Cedar (Thuja occidentalis L.) in a standard laboratory decay test to evaluate its resistance to decay by two decay fungi. Canada Yew was shown to be significantly more resistant to decay by Gloeophyllum trabeum (Pers.) Murr. (a brown rot fungus) and Trametes versicolor (L.: Fr.) Quél. (a white rot fungus) than Northern Red Oak (P ≤ 0.05). Canada Yew was shown to be equal to Eastern White Cedar in resistance to decay by G. trabeum and more than twice as resistant to decay by Trametes versicolor (P ≤ 0.05). These results may have relevance for survival of Canada Yew, which is under pressure from browsing by White-tailed Deer (Odocoileus virginianus).

Canataxpyran A, a novel 3,8-secotaxane with a 13,17-ether bridge from needles of Taxus canadensis

Abstract A novel 6/12-membered bicyclic taxane with a 13,17-ether bridge, named canataxpyran A, was isolated from the needles of Taxus canadensis. The structures were characterized as 7β,9,10β,20-tetracetoxy-13β,17-epoxy-3,8-secotaxa-3E,8E,11-triene-2α,5α-diol (designated as canataxpyran A, 1). This bicyclic taxane gradually decomposed in CDCl3to give the corresponding enones, 10β,20-diacetoxy-13β,17-epoxy-4α,5α-dihydroxy-3,8-secotaxa-2E,7E,11-trien-9-one (canataxpyran B, 2) and 5α,10β,20-triacetoxy-13β,17-epoxy-4α-hydroxy- 3,8-secotaxa-2E,7E,11-trien-9-one (canataxpyran C, 3). Compound 1 is the first example of a natural 3,8-secotaxane with 13,17-oxygen bridge.

A new taxane from Taxus canadensis needles

A new 6/8/6-membered taxane was isolated from the needles of Taxus canadensis. The structure was characterized as 10β,13α-diacetoxy-5α,9α-dihydroxytaxa-4(20),11-diene (1) on the basis of 1D and 2D spectrascopic data.

(S)-Styryl-α-alanine Used To Probe the Intermolecular Mechanism of an Intramolecular MIO-Aminomutase

A Taxus canadensis phenylalanine aminomutase (TcPAM) catalyzes the isomerization of (S)-α- to (R)-β-phenylalanine, making (E)-cinnamate (~10%) as a byproduct at steady state. A currently accepted mechanism for TcPAM suggests that the amino group is transferred from the substrate to a prosthetic group comprised of an amino acid triad in the active site and then principally rebinds to the carbon skeleton of the cinnamate intermediate to complete the α-β isomerization. In contrast, when (S)-styryl-α-alanine is used as a substrate, TcPAM produces (2E,4E)-styrylacrylate as the major product (>99%) and (R)-styryl-β-alanine (<1%). Comparison of the rates of conversion of the natural substrate (S)-α-phenylalanine and (S)-styryl-α-alanine to their corresponding products (k(cat) values of 0.053 ± 0.001 and 0.082 ± 0.002 s(-1), respectively) catalyzed by TcPAM suggests that the amino group resides in the active site longer than styrylacrylate. To demonstrate this principle, inhibition constants (K(I)) for selected acrylates ranging from 0.6 to 106 μM were obtained, and each had a lower K(I) compared to that of (2E,4E)-styrylacrylate (337 ± 12 μM). Evaluation of the inhibition constants and the rates at which both the α/β-amino acids (between 7 and 80% yield) and styrylacrylate were made from a corresponding arylacrylate and styryl-α-alanine, respectively, by TcPAM catalysis revealed that the reaction progress was largely dependent on the K(I) of the acrylate. Bicyclic amino donor substrates also transferred their amino groups to an arylacrylate, demonstrating for the first time that ring-fused amino acids are productive substrates in the TcPAM-catalyzed reaction.

Novel Taxa-4(20),12-diene and 2(3→20)Abeotaxane from Needles ofTaxus canadensis

A novel 6/8/6-membered taxane with a rare C-12(13)-double bond and rare 2(3→20)abeotaxane were isolated from the needles of Taxus canadensis. Their structures were characterized as 7β,9α,10β-triacetoxytaxa-4(20),12-diene-2α,5α,11β-triol (1) and 2α,7β,10β-triacetoxy-5α-hydroxy-2(3→20)abeotaxa-4(20),11-diene-9,13-dione (2) on the basis of 1D and 2D spectroscopic data. 1 is the first example of a natural taxane without substitution at both C-13 and C-14.

Separation of taxanes from Taxus canadensis using dynamic pressurized liquid extraction

An extraction technique, dynamic pressurized liquid extraction (DPLE), was proposed to extract the taxanes; including 10-DAB III, Baccatin III, 9-DHB III and paclitaxel, from powdered Taxus canadensis needles. A dual-solvent approach was adopted in which the impurities were firstly removed by extraction with hexane, and the taxanes were subsequently extracted with an appropriate solvent. The performance of chloroform, dichloromethane, and mixtures of methanol/dichloromethane was compared for use as the taxane-extracting solvent, and it was found that solvents containing a higher proportion of methanol had higher extraction capabilities. The effect of temperature on DPLE extraction of the taxanes was also studied, and it was found that higher extraction efficiencies could be realized with increasing temperature up to a threshold of 90°C. Based on a progressive conversion model, a kinetic equation for the extraction process was proposed. This model successfully confirmed that smaller needle powder particle sizes would result in higher extraction rates, which is consistent with the data obtained by experimentation.

Establishing a sustainable harvest for canada yew (Taxus canadensis marsh.) in Ontario

In 2003, commercial harvest of Canada yew (Taxus canadensis Marsh.) in Ontario began—but without a sustainable harvest policy. In 2005, we began to determine the sustainability of three harvest intensity treatments at three sites in central Ontario. Harvest treatments were labelled control (no initial harvest), light (two-year-old shoots removed), moderate (three-year-old shoots removed), and severe (seven-year-old shoots removed). We also looked at effects of harvest season and light levels on shoot regrowth. After three and four years, severe-harvest plants yielded less than half the biomass of the initial harvest, while biomass from moderate-harvest plants was about equal to the initial. Biomass from light-harvest plants generally increased. Moderate light levels stimulated more first-year regrowth in all plants than low light levels did but increased only Year 2 regrowth in severe-harvest plants. Spring harvest reduced first-year regrowth only. Comparing biomass of moderate-harvest plants after three or four years with initial moderate-harvest biomass suggested similar growth rate across time periods. Our results concur with Canada Yew Association sustainable harvest guidelines: Moderately harvesting three-year-old shoots plus allowing four years of regrowth before reharvest ensures sustainable harvest, at least through one harvest cycle.

Chemical Constituents from the Needles of Taxus canadensis

Aim To study the chemical constituents of Taxus canadensis. Method The constituents were isolated by various chromatographic methods, and the chemical structures were elucidated on the basis of spectral analysis. Results Six known compounds were isolated and identified as p-hydroxybenzoic acid ( 1), putraflavone ( 2), sequoiavone ( 3), 7, 13-dideacetyl-9, 10-debenzoyltaxchinin C ( 4), baccatin VI ( 5) and taxumairone A ( 6). Conclusion Compounds 1 and 2 were isolated from this genus for the first time, and compounds 3–6 were isolated from Taxus canadensis for the first time.

Efficient purification of paclitaxel from yews using high-performance displacement chromatography technique

Paclitaxel was purified using high-performance displacement chromatography (HPDC) technique, but not by the mechanism of HPDC. On small scale, paclitaxel was extracted with methanol from dry needles of Taxus canadensis and was enriched by extracting with chloroform after removing water-soluble hydrophilic components and hexane-soluble hydrophobic components. Then, 93–99% purity of paclitaxel was obtained using the HPDC technique. On large scale, taxanes were enriched by solvent partitioning between acetic acid/MeOH/H 2O and hexane and extracted with CH 2Cl 2. Taxanes except paclitaxel were further removed by extracting with methanol–water–trifluoroacetic acid (1.0:98.9:0.1, v/v/v). Applying HPDC technique to water-insoluble substances is problematic as this method requires a highly aqueous solvent system. In order to overcome this incompatibility, a system was set up where paclitaxel, although in low concentration, was extracted by methanol–water–trifluoroacetic acid (10.0:89.9:0.1, v/v/v). Recycling the extracting solvent to ensure minimal volume, the extracted paclitaxel was adsorbed on a C 18 trap column. A C 18 column of 4.6 mm internal diameter was then connected to the trap column. The HPDC technique was thus carried out using an isocratic acetonitrile–water–trifluoroacetic acid (30.0:69.9:0.1, v/v/v) mobile phase consisting of a displacer cetylpyridinium trifluoroacetate (3 mg/mL). Paclitaxel was co-eluted with the displacer and spontaneously crystallized. The crystal (114 mg) showed 99.4% purity and only 10% of paclitaxel in the starting crude extract was lost during the enrichment/purification processes. This large scale purification method was successfully applied to purify paclitaxel from Chinese yew in small scale, suggesting general applicability of the method. This is the first report of purifying a water-insoluble natural product using HPDC technique.

ChemInform Abstract: Two New Phytoecdysteroids from the Needles of Taxus canadensis.

AbstractTwo new phytoecdysteroids with a 20,22‐acetal group are identified for the first time from the needles of the Canadian yew, Taxus canadensis.

The ecology of Canada Yew (Taxus canadensisMarsh.): A review

Canada yew (Taxus canadensis Marsh.) is a shade-tolerant evergreen shrub native to the understories of the boreal and deciduous forests of northeastern North America. Canada yew has a relatively unique growth form, with low sprawling branches capable of forming dense clusters of stems. Historic accounts suggest that before Euro-American settlement, Canada yew was a common plant across its range in many forest types and that it was locally abundant or dominant in 5%–20% of forest stands in the northern part of its range. Canada yew’s range has declined during the last century as a result of browsing by native ungulates, fire, intensive forest management, and clearing of land for agriculture and other development. It is considered uncommon throughout most of its present North American range, except for often isolated populations in areas that remain free from heavy browsing pressure by moose and deer (e.g., islands, areas with heavy snow cover, or areas naturally low in ungulate abundance). Its decline has likely resulted in changes to abiotic and biotic conditions, including structure and composition of understory vegetation and concomitant effects on understory vertebrates. Increasing white-tailed deer populations and reduced snowfall as a result of climate change in eastern North America threaten to extirpate this species from additional parts of its range in the next century. Suggestions for future research are discussed.

The first taxane peroxide from the rooted cuttings of Taxus canadensis

The first taxane peroxide from the rooted cuttings of Taxus canadensis

Two New Phytoecdysteroids from the Needles of Taxus canadensis

Two new phytoecdysteroids with a 20,22-acetal group were identified for the first time from the needles of the Canadian yew, Taxus canadensis. Their structures were characterized as ponasterone A 20,22-p-hydroxybenzylidene acetal (1) and ponasterone A 20,22-acetonide (2) on the basis of 1D, 2D NMR evidence and high-resolution FABMS analysis

Allometric models for predicting the aboveground biomass of Canada yew (Taxus canadensis Marsh.) from visual and digital cover estimates

The objectives of this study were to evaluate visual and digital estimates of percent cover as source data and to develop cover-based allometric models for the prediction of aboveground biomass of Canada yew ( Taxus canadensis Marsh.). Cover was determined from visual assessment and digital images captured over 25 plots (1 m2) at a model training site near Timmins, Ontario. Linear and power functions were fit to the cover–biomass data to develop models of foliage, stem, and total aboveground biomass. Both sources of cover data produced models that explained between 70% and 85% of the variance in the training data, with root mean square error estimates ranging from 27 g·m–2 (foliage) to 85 g·m–2 (total). Models based on visual cover data performed consistently better and were tested on independent data. Stem and total biomass were underestimated in the model testing data set; however, prediction statistics indicated that the linear and power forms of foliage biomass models were validated by the testing data. Final models of foliage biomass were developed from the entire data set, with mean absolute errors of 18.3 and 18.7 g·m–2 for the linear and power forms, respectively. Additional variables (e.g., plant height, age) may be required to provide general predictions of the woody biomass of Canada yew.

Death and Taxus: the high cost of palatability for a declining evergreen shrub, Taxus canadensis

Taxus canadensis Marsh., a shade-tolerant evergreen shrub, is in decline as a result of past anthropogenic disturbances and increased cervid browsing. To identify factors that may be influencing establishment for this species, we planted 1080 T. canadensis cuttings in a hemlock–hardwood forest in the spring of 2004. Cuttings were planted across a gradient of light environments, consisting of artificial canopy gaps (61–441 m2) and closed-canopy conditions, and half were protected with deer exclosures. Following four growing seasons, T. canadensis survival in exclosures was 92% compared with 75% in controls. A mixed-effects binary logistic regression analysis revealed that deer exclusion had the most influence on the probability of survival; all else being equal an individual was nearly seven times more likely to survive if planted inside an exclosure (P &lt; 0.001). Increasing light intensity had a counterbalancing effect on growth and survival; light increased leader growth (P = 0.019) but reduced an individual’s probability of survival (P &lt; 0.001), possibly owing to enhanced herbivory and elevated moisture stress. Consequently, enhancing resource availability and growth may not decrease the impact of biomass loss to herbivory. These results suggest that even with relatively low herbivore densities, exclosures are required for the recovery of highly palatable species.

Two New 11(15→1)Abeotaxanes with a 2,20-Epoxy Ring from the Needles of Taxus canadensis

Two 11(15-->1)abeotaxanes having a tetrahydrofuran ring along the carbon atoms C-2, C-3, C-4, C-20 were identified for the first time from the needles of the Canadian yew, Taxus canadensis. The compounds could be identified as 4alpha,10beta,13alpha-triacetoxy-15-benzoyloxy-2alpha,20beta-epoxy-11(15-->1)abeotax-11-ene-5alpha,7beta,9alpha-triol (1) and 4alpha,7beta,9alpha,10beta,15-pentaacetoxy-2alpha,20beta-epoxy-11(15-->1)abeotax-11-ene-5alpha,13alpha-diol (2) on the basis of 1D-, 2D-NMR evidence and high-resolution FABMS analysis. Compound 1 showed weak growth inhibitory activities against T-98 and MM1-CB cells in vitro.

A pair of taxoids from the needles of Taxus canadensis

A pair of taxoids were isolated from the needles of Taxus canadensis, which were identified as 2,10-diacetyl-5(Z)-cinnamoylphototaxicin II (1), a new taxoid, and 2,10-diacetyl-5(E)-cinnamoylphototaxicin II (2), a known one, by spectroscopic methods including 1H, 13C NMR, HSQC, HMBC, NOESY, and mass spectra.