Abstract

   Ephedra is one of the world’s most important plants, used in medicine,
   plants and ecology. Most Ephedra grows in plain areas and is stable.
   But the plateau environment is special, with the change of altitude,
   the variety difference of plateau Ephedra saxatilis is very obvious. E.
   saxatilis metabolism on the Tibetan Plateau is not only affected by
   altitude, but also environmental conditions such as climate conditions
   and different soil components. However, the change mechanism of E.
   saxatilis alkaloids in special ecological environment is still unclear.
   Therefore, we analyzed the metabolic and altitude of E. saxatilis
   species in the Tibetan Plateau. Through the functional analysis of
   Kyoto Metabolism and Metabolomic Encyclopedia (KEGG), we can determine
   that the number of E. saxatilis metabolites decreases with the increase
   of altitude, and there are differences in metabolism among the three
   mountains. This was confirmed by univariate analysis of the top five
   metabolic pathways. Based on the analysis of soil and metabolomics, it
   was found that soil water content was also a factor affecting E.
   saxatilis metabolism. According to the difference of vertical height
   gradient, ephedrine and pseudephedrine showed the same change in
   vertical altitude under different mountains. Ephedrine increased as the
   altitude gradient increased, and pseudoephedrine decreased as the
   altitude gradient decreased. Our results provide valuable information
   for further study of metabolic mechanism and efficacy stability. It
   provides useful reference for the research of E. saxatilis planting in
   special area.

1 Introduction

   The medicinal resources of Ephedra are very rich, the metabolites in
   the body such as ephedrine, polysaccharide, flavonoids and so on are
   very rich [[34]1]. The stems of some Ephedra (ephedraceae) are rich in
   metabolites such as ephedrine and pseudoephedrine, effective for
   headaches, bronchial asthma, rhinitis, and the common cold [[35]2].
   With the research of Ephedra more and more in-depth, people found that
   Ephedra contains a variety of chemical components, such as volatile
   oil, flavonoids, polysaccharides, amino acids, tannins, organic acids,
   lignans and trace elements, but alkaloids is still the most important
   medicinal ingredients of Ephedra [[36]3–[37]5].

   Ephedra is distributed in 40 groups all over the world, such as Japan,
   Nepal, Uzbekistan, China and so on [[38]6–[39]9]. There are about 6
   species in the southern Tibet Plateau of China. The Tibetan Plateau and
   its adjacent areas have strong ecosystem diversity and vegetation is
   obviously affected by local climate and topography [[40]10]. Previous
   studies on Ephedra mostly focused on the phylogeographic structure,
   phylogenetic reconstruction and chemical substances [[41]11, [42]12].
   However, ecological investigation of the effects of altitude on
   alkaloids has not been established. E. saxatilis, which is unique to
   Tibet in China, E. saxatilis is difficult to pick due to its high
   altitude, so the analysis of ephedrine and pseudoephedrine can find the
   factors that determine its stable efficacy, which can provide
   references for our later cultivation of E. saxatilis and provide a