Identifying Three Ecological Chemotypes of Xanthium strumarium Glandular Trichomes Using a Combined NMR and LC-MS Method

Abstract

Xanthanolides, as the sesquiterpene lactones, are reportedly the major components for the pharmacological properties of X. strumarium L. species. Phytochemical studies indicated that the glandular structures on the surface of plant tissues would form the primary sites for the accumulation of this class of the compounds. As the interface between plants and their natural enemies, glandular trichomes may vary with respect to which of their chemicals are sequestered against different herbivores in different ecologies. However, to date, no data are available on the chemical characterisation of X. strumarium glandular cells. In this study, the trichome secretions of the X. strumarium species originating from nineteen unique areas across eleven provinces in China, were analysed by HPLC, LC-ESI-MS and NMR. For the first time three distinct chemotypes of X. strumarium glandular trichomes were discovered along with the qualitative and quantitative evaluations of their presence of xanthanolides; these were designated glandular cell Types I, II, and III, respectively. The main xanthanolides in Type I cells were 8-epi-xanthatin and xanthumin while no xanthatin was detected. Xanthatin, 8-epi-xanthatin, and xanthumin dominated in Type II cells with comparable levels of each being present. For Type III cells, significantly higher concentrations of 8-epi-xanthatin or xanthinosin (relative to xanthatin) were detected with xanthinosin only being observed in this type. Further research will focus on understanding the ecological and molecular mechanism causing these chemotype differences in X. strumarium glandular structures.

Comparative Transcriptome Analysis Identifies Putative Genes Involved in the Biosynthesis of Xanthanolides in Xanthium strumarium L.

“…The glandular trichome-specificity of xanthanolide biosynthesis in X. strumarium has also been described recently (Chen et al, 2013). In general, a low expression of pathway genes in specialized cells is one of the major challenges to investigating plant secondary metabolism.…”

“…The young leaves of the Zunyi-cultivar also synthesize xanthanolides (Chen et al, 2013), indicating that the gene transcripts for xanthanolide biosynthesis are present in the leaves of Zunyi-cultivar as well. Thus, in addition to the glandular trichome-specificity, the common presence of gene transcripts in both the Hubei- and Zunyi-cultivars was considered as the second filter in reducing the number of candidate genes.…”

Chemical defense against insects in Heterotheca subaxillaris and three Orobanchaceae species using exudates from trichomes

“…Xanthanolides produced by Xanthium sp. are also stored in glandular trichomes and play a role in herbivore resistance …”

“…are also stored in glandular trichomes and play a role in herbivore resistance. 16,17 There have been several reports about phytochemicals, including monoterpenes, cadinenes, and calamenenes, in camphorweed. 18,19 There was a notable report that the productivity of these terpenes was changed by the nitrogen content in environmental soil.…”

Differential microRNA Analysis of Glandular Trichomes and Young Leaves in Xanthium strumarium L. Reveals Their Putative Roles in Regulating Terpenoid Biosynthesis

“…Previously, we discovered that xanthanolides were highly biosynthesized and accumulated in the glandular trichomes of the X . strumarium tissues, especially on its leaves at early stage [ 40 ]. To identify genes encoding enzymes involved in trichome-dependent biosynthesis of xanthanolides in X .…”