Seasonal changes in the concentrations of four taxoids in Taxus baccata L-during the autumn-spring period

The concentrations of four common taxoids: baccatin III, paclitaxel, cephal omannine and 10-deacetylbaccatin III (10-DAB III) were measured in fresh ne edles and stems of Taxus baccata L. during the late autumn-spring period (N ovember '96 - April '97) which has not been investigated to date in this sp ecies. Baccatin III, paclitaxel and 10-DAB III were present on the surface of the twigs in concentrations of 8-26 mu g/1000 g (fresh weight). Changes in the levels of baccatin III and paclitaxel inside the needles and stems s howed similar trends over the investigated period. From November to March t he total level of taxoids differed between the needles and stems, and were the same only in April. Total levels in fresh needles were stable from Dece mber to March. The highest concentrations of 10-DAB III in the whole analys ed period in fresh stems were measured, as well as in the fresh needles exc ept for samples collected in November and December when the levels of cepha lomannine were higher. The concentrations of paclitaxel were usually the lo west. These results confirm that epigenetic factors - date of collection (a nd thus phyllogenesis) and kind of plant tissue - determine taxoid levels d uring the late autumn-spring period in T. baccata. The opposite patterns of changes for 10-DAB III and cephalomannine, especially in the fresh needles , suggest a possible role for 10-DAB III in the biosynthetic pathway to cep halomannine, a less polar taxoid with a side-chain at position C-13. As wel l, owing to the thermolability of taxoids, the influence of low temperature s in December and January could explain the highest observed concentrations of 10-DAB III in the fresh stems and needles, respectively.