Omanische Heilpflanze im Fokus der Phytochemie IPB-Wissenschaftler und Partner aus Dhofar haben jüngst die omanische Heilpflanze Terminalia dhofarica unter die phytochemische Lupe genommen. Die Pflanze ist reich an…
Geschmack ist vorhersagbar: Mit FlavorMiner. FlavorMiner heißt das Tool, das IPB-Chemiker und Partner aus Kolumbien jüngst entwickelt haben. Das Programm kann, basierend auf maschinellem Lernen (KI), anhand der…
Brandt, W.; Manke, K.; Vogt, T.;A catalytic triad – Lys-Asn-Asp – Is essential for the catalysis of the methyl transfer in plant cation-dependent O-methyltransferasesPhytochemistry113130-139(2015)DOI: 10.1016/j.phytochem.2014.12.018
Crystal structure data of cation-dependent catechol O-methyltransferases (COMTs) from mammals and related caffeoyl coenzyme A OMTs (CCoAOMTs) from plants have suggested operative molecular mechanisms. These include bivalent cations that facilitate deprotonation of vicinal aromatic dihydroxy systems and illustrate a conserved arrangement of hydroxyl and carboxyl ligands consistent with the requirements of a metal-activated catalytic mechanism. The general concept of metal-dependent deprotonation via a complexed aspartate is only one part of a more pronounced proton relay, as shown by semiempirical and DFT quantum mechanical calculations and experimental validations. A previously undetected catalytic triad, consisting of Lys157-Asn181-Asp228 residues is required for complete methyl transfer in case of a cation-dependent phenylpropanoid and flavonoid OMT, as described in this report. This triad appears essential for efficient methyl transfer to catechol-like hydroxyl group in phenolics. The observation is consistent with a catalytic lysine in the case of mammalian COMTs, but jettisons existing assumptions on the initial abstraction of the meta-hydroxyl proton to the metal stabilizing Asp154 (PFOMT) or comparable Asp-carboxyl groups in type of cation-dependent enzymes in plants. The triad is conserved among all characterized plant CCoAOMT-like enzymes, which are required not only for methylation of soluble phenylpropanoids like coumarins or monolignol monomers, but is also present in the similar microbial and mammalian cation-dependent enzymes which methylate a comparable set of substrates.
The male gametophyte of higher plants appears as a solid box containing the essentials to transmit genetic material to the next generation. These consist of haploid generative cells that are required for reproduction, and an invasive vegetative cell producing the pollen tube, both mechanically protected by a rigid polymer, the pollen wall, and surrounded by a hydrophobic pollen coat. This coat mediates the direct contact to the biotic and abiotic environments. It contains a mixture of compounds required not only for fertilization but also for protection against biotic and abiotic stressors. Among its metabolites, the structural characteristics of two types of phenylpropanoids, hydroxycinnamic acid amides and flavonol glycosides, are highly conserved in Angiosperm pollen. Structural and functional aspects of these compounds will be discussed.
Publikation
Farag, M. A.; Sakna, S. T.; El-fiky, N. M.; Shabana, M. M.; Wessjohann, L. A.;Phytochemical, antioxidant and antidiabetic evaluation of eight Bauhinia L. species from Egypt using UHPLC–PDA–qTOF-MS and chemometricsPhytochemistry11941-50(2015)DOI: 10.1016/j.phytochem.2015.09.004
Bauhinia L. (Fabaceae) comprises ca. 300–350 plant species, many of which are traditionally used in folk medicine for their antidiabetic, antioxidant and anti-inflammatory effects. Bauhinia s.l. recently has been subdivided into 9 genera based on phylogenetic data: Bauhinia s.str., Barklya, Brenierea, Gigasiphon, Lysiphyllum, Phanera, Piliostigma, Schnella (American Phanera) and Tylosema. The aerial parts of 8 species corresponding to 5 genera were analyzed: Bauhinia forficata, Bauhinia variegata, B. variegata var. candida, Bauhinia galpinii, Schnella glabra, Piliostigma racemosa, Phanera vahlii and Lysiphyllum hookeri. Leaves and shoots were subjected to metabolite profiling via UHPLC–PDA–qTOF-MS coupled to multivariate data analyzes to identify compound compositional differences. A total of 90 metabolites were identified including polyphenols and fatty acids; flavonoid conjugates accounted for most of the metabolite variation observed. This study provides a comprehensive map of polyphenol composition in Bauhinia and phytochemical species aggregations are consistent with recent Bauhinia genus taxonomic relationship derived from phylogenetic studies. DPPH radical scavenging and α-glucosidase inhibitory assays were also performed to assess selected aspects of the antioxidant and antidiabetic potential for the examined species with respect to metabolite profiles.
Publikation
Otto, A.; Porzel, A.; Schmidt, J.; Wessjohann, L.; Arnold, N.;A study on the biosynthesis of hygrophorone B12 in the mushroom Hygrophorus abieticola reveals an unexpected labelling pattern in the cyclopentenone moietyPhytochemistry118174-180(2015)DOI: 10.1016/j.phytochem.2015.08.018
The hitherto unknown natural formation of hygrophorones, antibacterial and antifungal cyclopentenone derivatives from mushrooms, was investigated for hygrophorone B12 in Hygrophorus abieticola Krieglst. ex Gröger & Bresinsky by feeding experiments in the field using 13C labelled samples of d-glucose and sodium acetate. The incorporation of 13C isotopes was extensively studied using 1D and 2D NMR spectroscopy as well as ESI-HRMS analyses. In the experiment with [U-13C6]-glucose, six different 13C2 labelled isotopomers were observed in the 2D INADEQUATE spectrum due to incorporation of [1,2-13C2]-acetyl-CoA. This labelling pattern demonstrated that hygrophorone B12 is derived from a fatty acid-polyketide route instead of a 1,4-α-d-glucan derived anhydrofructose pathway. The experiment with [2-13C]-acetate revealed an unexpected incorporation pattern in the cyclopentenone functionality of hygrophorone B12. Four single-labelled isotopomers, in particular [1-13C]-, [2-13C]-, [3-13C]-, and [4-13C]-hygrophorone B12, were detected that showed only half enrichment in comparison to the respective labelled alkyl side chain carbons. This labelling pattern indicates the formation of a symmetrical intermediate during hygrophorone B12 biosynthesis. Based on these observations, a biogenetic route via a 4-oxo fatty acid and a chrysotrione B homologue is discussed.