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.
Highlights
X. strumarium L. is an annual herb that belongs to the Asteraceae family [1]
Xanthanolide biosynthesis was associated with the distribution of glandular cells on X. strumarium organs
Peak1 (Peak 1 was assigned to xanthumin by the following NMR analysis in this study) had a strong UV absorption at around 280 nm, whereas Peak2 (Peak 2 was assigned to 8-epi-xanthatin by the following NMR analysis in this study) showed a maximum UV absorption at less than 210 nm (Figure S2)
Summary
X. strumarium L. is an annual herb that belongs to the Asteraceae family [1]. The plant is traditionally used for the treatment of rhinitis, rheumatism, tuberculosis, cancer, ulcers and malaria [2,3,4,5]. The xanthanolides have been considered as a promising drug against methicillinresistant Staphylococcus aureus [12]. Despite their pharmaceutical importance, the biosynthesis of the xanthanolide sesquiterpene lactones in X. strumarium remains largely unknown. The biosynthesis of the xanthanolide sesquiterpene lactones in X. strumarium remains largely unknown To understand their specialised metabolism, it is essential to know which tissue or specific structures in the plants are the primary sites for biosynthesising the targeted compounds.
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