Natural product analysis and metabolic studies

Identification of natural products with ecological implications from natural sources is a major task of our work (Schneider, 2013, eMagRes 2, 451–466). Samples from phenylphenalenone-producing plant families (e.g. the Haemodoraceae and the Musaceae), from Arabidopsis thaliana (Bednarek et al., 2009, Science 323, 101-106), Nicotiana attenuata (Heiling et al., 2009, Plant Cell 22, 273-292), Papaver nudicaule (Tatsis et al., 2013, Org. Lett. 15, 156–159), and Picea abies (Li et al., 2008, Phytochemistry 69, 772-782) were recently studied together with internal or external collaborators or originate from projects of our group, respectively. Products of isolated or recombinant enzymes are another important group of compounds for NMR-spectroscopic analysis (Schneider, 2010, Prog. Bot. 72, 183-206; Jirschitzka et al., 2012, PNAS 109, 10304-10309). The samples (isolated compounds, extracts, pre-separated fractions) are subject to 1D and 2D NMR analysis, including quantification. In addition to plant-derived natural products, antibiotics from beewolf-symbiotic streptomycetes (Kroiss et al., 2010, Nature Chem. Biol. 6, 261-263) (collaboration with M. Kaltenpoth) and a fish pheromone released by dominant tilapia males have been identified (collaborative project with researchers from the University of Algarve, Portugal; Keller-Costa et al., 2014, Curr. Biol. 24, 2130-2135). Cryogenically cooled probeheads, operating at a proton resonance frequency of 500 MHz and 700 MHz, are available for measuring mass-limited samples. LC-DAD-MS-NMR coupling is especially useful to identify natural products without isolation.

Biosynthetic stable-isotope labelling studies (Schneider, 2007, Prog. NMR Spectr. 51, 155-198) are carried out by administering labeled precursors to plant tissue or root cultures or by incubating plants under 18O or 13CO2 atmosphere. NMR and MS analyses of the target molecules provide information about precursor-product relationships, biosynthetic pathways and other metabolic processes (Munde et al., 2011, Phytochemistry 72, 49-58; Munde et al., 2013, Phytochemistry 91, 165-176; Tatsis et al., 2014, ChemBioChem 15, 1645-1650).