Seasonal variation of neutral and basic taxoid contents in shoots of European Yew ( Taxus baccata)

Abstract

Seasonal variations of taxoid constituents were determined in shoots of European Yew collected from two locations. The first samples originated from a male Taxus baccata tree growing in Gif, France. The second samples were obtained from genetically identical female Irish Yew trees ( T. baccata var. fastigiata), of the same age and growing at one site in Dublin, Ireland. Shoots were collected monthly for one year and separated into needles and stems. Neutral taxoids (paclitaxel and 10-deacetylbaccatin III (10-DAB III)) and basic taxoids (including taxines B) were extracted and quantified. Needles yielded significantly higher levels of taxoids than stems. 10-DAB III contents in needles of French samples showed considerable monthly fluctuations, while in needles of the Irish samples maximum yields of 10-DAB III were found in June. Highest levels of paclitaxel were present between February and April. Basic taxoids occurred in highest concentrations (total alkaloids 9.49 g/kg) in the August collection of French samples, but in needles of the Irish Yew in November and December (total alkaloids 16.9 g/kg; taxines B 10.9 g/kg). No conclusion could be drawn as to the optimum time of year for harvesting, since this varies from tree to tree, depending on T. baccata variety, location and taxoid type.