Polyesters of 14-Hydroxylated Taxoids Found for the First Time in <i>Taxus canadensis</i> Intact Plants

Abstract

Taxane diterpenoids (taxoids) are found only in representatives of the Taxaceae family (different yew species); however, the unique structure and therapeutic properties of taxoids, which are in demand in medicine, have made these compounds one of the most studied secondary metabolites of higher plants. In this work, for the first time, a detailed study is performed into the structural diversity of polyesters of 14-hydroxylated taxoids in Taxus canadensis a yew species, for intact plants of which nonpolar 14-hydroxylated taxoids have not been previously described. At the first stage of the work, it was shown using chromato-mass spectrometry that polyesters of 14-hydroxylated taxoids (yunnanxan, taxuyunnanin C, sinenxan B, sinenxan C) are the dominant diterpenoid secondary metabolites in T. canadensis callus cell culture. Based on these results, as well as the similarity of the metabolism of cultivated in vitro plant cells and root cells in planta, it was suggested that polyesters of 14-hydroxylated taxoids will preferentially accumulate in the roots in intact T. canadensis plants. The validity of this hypothesis was confirmed using liquid chromatography-mass spectrometry and nuclear magnetic resonance spectroscopy (NMR). According to chromato-mass-spectrometric screening in T. canadensis needles, polyesters of 14-hydroxylated taxoids are actually found only in trace amounts, while they are one of the major (quantitatively) diterpenoids in the roots. One of the main 14-hydroxylated taxoids of T. canadensis roots, yunnanxan, was isolated preparatively and uniquely identified using NMR spectroscopy and high-resolution mass spectrometry. This work is the first report on the presence of polyesters of 14-hydroxylated taxoids in intact Canadian yew plants.