Bioprospecting of plant natural products in Schleswig-Holstein (Germany) I: chemodiversity of the Cichorieae tribe (Asteraceae) in Schleswig-Holstein

Abstract

Recent international developments make access to biological resources across international borders more difficult than in the past. Local access to biological resources, including plant natural products, thus becomes more important. In order to evaluate the opportunities to access bioactive natural products in our region, we here start a series of dedicated articles assessing the chemical diversity of plant taxa, native and naturalized, in the region of Schleswig-Holstein, Germany. The region has only a limited biodiversity with about 1500 species of higher plants growing in the wild. Our aims are the following: (1) A complete review of the natural products reported from taxa occurring in Schleswig-Holstein from any part of their distribution range. (2) Proof or disproof, whether these substances are also occurring in populations of the taxa at hand occurring in the wild in Schleswig-Holstein. (3) To establish analytical GLC-MS and/or HPLC-DAD-MS systems to identify and quantify these compounds. (4) Initiation of dedicated efforts to unravel the array of secondary metabolites contained in species from the Schleswig-Holstein region not yet investigated. (5) Search for chemically defined intraspecific taxa, i.e. chemically differing lineages of morphologically indistinguishable plant taxa, by comparing plants from Schleswig-Holstein with plants collected in other regions. The survey into the plant natural products’ chemodiversity of the flora of Schleswig-Holstein begins with a review of the natural products from Schleswig-Holstein members of the Cichorieae tribe of the Asteraceae family. The Cichorieae tribe of the Asteraceae family, which encompasses 94 genera and about 1500 species and innumerous microtaxa worldwide (Kilian et al. in Systematics, evolution and biogeography of the Compositae, IAPT, Vienna, 2009), is represented by only 17 genera in Schleswig-Holstein: Arnoseris, Chondrilla, Cicerbita, Cichorium, Crepis, Hieracium, Hypochaeris, Lactuca, Lapsana, Leontodon, Picris, Pilosella, Scorzonera, Scorzoneroides, Sonchus, Taraxacum, and Tragopogon. In total, 48 species (50 taxa including the two species with two distinct subspecies each in the region and treating the sections in the hyper-species-rich genus Taraxacum as species here), occur in Schleswig-Holstein. For all of the genera and all but six of the species (Hieracium fuscocinereum, Lactuca macrophylla, Sonchus palustris, and Taraxacum sections Celtica, Hamata, and Obliqua), the array of plant natural products has already been investigated to some degree. However, for only two taxa (Pilosella officinarum and Tragopogon pratensis subsp. minor) also plants from the region of Schleswig-Holstein have been studied and for only very few taxa, such as Cichorium intybus and Taraxacum officinale, all major classes of natural products have been investigated in detail so far.