Taxol formation in yew — Taxus

Abstract

In Pacific yew, Taxus brevifolia, taxol is found most abundantly in the vascular cambial region followed by the phloem, sapwood and heartwood. It is in this order that ‘in vitro’ taxol biosynthetic activity was also demonstrated using [1- 14C]acetate as a precursor. However, only traces of taxol biosynthesis could be demonstrated in the xylem (sapwood-heartwood) suggesting that taxol may be mobilized from its place of greatest biosynthetic activity (vascular cambial region) to the xylem; perhaps via ray parenchyma. Taxol could also be effectively trapped under ‘bark flaps’, over a period of several weeks, using silica gel powder as an adsorbant. In vitro taxol biosynthesis using [1- 14C]acetate in outer bark samples (cambium-phloem) could only be demonstrated in Taxus brevifolia, Taxus floridana and Taxus canadensis, among 10 of the 11 native Taxus species tested.