Taxanes in Taxus baccata pollen: cardiotoxicity and/or allergenicity?

Diterpenic alkaloids belonging to taxine (yield: 0.18 % dry weight) and taxoids (paclitaxel, baccatine III and 10-deacetylbaccatine III, cumulated yield: 0.004 % dry weight) were isolated from Taxus baccata L. pollen. Moreover, taxoids conjugated to macromolecules were also detected by ELISA. According to these data and to semi-quantitative measurements of pollen production, a hundred-year-old yew during its flowering time releases several grams of taxanes contained in 16 to 20 kg of pollen. Toxicity assays on mice indicated that any risk of acute toxicity resulting from Taxus pollen inhalation and subsequent taxine absorption is unlikely. On the other hand, anti-paclitaxel IgG were above all detected in sera of subjects displaying hypersensitivity reactions during the pollination periods of Taxus sp. and Betula sp. This natural anti-paclitaxel IgG acquisition by individuals living in the distribution areas of these trees could be at the origin of atopic manifestations. We also postulate that such a natural sensitization could have a marked influence on the tolerance to anticancer taxoids.