Chemical and morphological variability of Taxus : needles, seeds and cell cultures

Abstract

The genus Taxus (family Taxaceae) has during the last 30-40 years been the subject of extensive scientific investigation due to the discovery of the anti-cancer drug paclitaxel (Taxol) originally isolated from the bark of the Pacific yew tree (T. brevifolia). Worldwide demand for paclitaxel is high as it is currently being used to treat breast, ovarian and non-small cell lung cancers as well as AIDS-related Kaposi’s sarcoma. This has led to problems with sustainable supply from renewable sources and alternative means to production of paclitaxel are still under extensive investigation. Major problems associated with paclitaxel production include (i) the correct identification of the species within the genus Taxus in order to comply with FDA licence agreements and (ii) production of sufficient biomass either in the form of plant material or in vivo production of taxanes. One of the main objectives in this research was to address the problem of correct identification of Taxus species and cultivars and to evaluate the species delimitation within the genus. Morphological characteristics such as needle and seed dimensions combined with classical morphological characteristics (foliage colour and tree shape) were analysed from a large population of Taxus species and cultivars. The analysis of needle and seed dimensions was done using a computerised image analysis software-package called WinSEEDLE™. All measurements complied with literature values and no single parameter was found that could distinguish between one species and another.