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Publikationen - Natur- und Wirkstoffchemie

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Publikation

Dumri, K.; Seipold, L.; Schmidt, J.; Gerlach, G.; Dötterl, S.; Ellis, A. G.; Wessjohann, L. A.; Non-volatile floral oils of Diascia spp. (Scrophulariaceae) Phytochemistry 69, 1372-1383, (2008) DOI: 10.1016/j.phytochem.2007.12.012

The floral oils of Diascia purpurea, Diascia vigilis, Diascia cordata, Diascia megathura, Diascia integerrima and Diascia barberae (Scrophulariaceae) were selectively collected from trichome elaiophores. The derivatized floral oils were analyzed by gas chromatography–mass spectrometry (GC–MS), whilst the underivatized samples were analysed by electrospray ionization mass spectrometry (ESI-MS) and Fourier-transform ion cyclotron resonance mass spectrometry (FTICR-MS). The most common constituents of the floral oils investigated are partially acetylated acylglycerols of (3R)-acetoxy fatty acids (C14, C16, and C18), as was proven with non-racemic synthetic reference samples. The importance of these oils for Rediviva bees is discussed in a co-evolutionary context.
Publikation

Cuong, N. M.; Wilhelm, H.; Porzel, A.; Arnold, N.; Wessjohann, L.; 1-O-Substituted derivatives of murrayafoline A and their antifungal properties Nat. Prod. Res. 22, 950-954, (2008) DOI: 10.1080/14786410701650212

The synthesis of some 1-oxygenated derivatives of murrayafoline A (1) and their antifungal properties is reported. Three derivatives, 1-hydroxy-3-methyl-9H-carbazole (2), 1-(3-methylbut-2-enyloxy)-3-methyl-9H-carbazole (3) and 1-(2,3,4,6,-tetra-O-acetyl-α-D-O-glucopyranosyl)-3-methyl-9H-carbazole (4), of murrayafoline A were synthesized. Compounds 1 and 2 exhibit strong fungicidal activity against Cladosporium cucumerinum at the dose of 12.5 µg.
Publikation

Burse, A.; Frick, S.; Schmidt, A.; Buechler, R.; Kunert, M.; Gershenzon, J.; Brandt, W.; Boland, W.; Implication of HMGR in homeostasis of sequestered and de novo produced precursors of the iridoid biosynthesis in leaf beetle larvae Insect Biochem. Mol. Biol. 38, 76-88, (2008) DOI: 10.1016/j.ibmb.2007.09.006

Insects employ iridoids to deter predatory attacks. Larvae of some Chrysomelina species are capable to produce those cyclopentanoid monoterpenes de novo. The iridoid biosynthesis proceeds via the mevalonate pathway to geranyl diphospate (GDP) subsequently converted into 8-hydroxygeraniol-8-O-β-d-glucoside followed by the transformation into the defensive compounds. We tested whether the glucoside, its aglycon or geraniol has an impact on the activity of 3-hydroxy-3-methylglutaryl-CoA reductase (HMGR), the key regulatory enzyme of the mevalonate pathway and also the iridoid biosynthesis. To address the inhibition site of the enzyme, initially a complete cDNA encoding full length HMGR was cloned from Phaedon cochleariae. Its catalytic portion was then heterologously expressed in Escherichia coli. Purification and characterization of the recombinant protein revealed attenuated activity in enzyme assays by 8-hydroxygeraniol whereas no effect has been observed by addition of the glucoside or geraniol. Thus, the catalytic domain is the target for the inhibitor. Homology modeling of the catalytic domain and docking experiments demonstrated binding of 8-hydroxygeraniol to the active site and indicated a competitive inhibition mechanism. Iridoid producing larvae are potentially able to sequester glucosidically bound 8-hydroxygeraniol whose cleavage of the sugar moiety results in 8-hydroxygeraniol. Therefore, HMGR may represent a regulator in maintenance of homeostasis between de novo produced and sequestered intermediates of iridoid metabolism. Furthermore, we demonstrated that HMGR activity is not only diminished in iridoid producers but most likely prevalent within the Chrysomelina subtribe and also within the insecta.
Publikation

Brock, A.; Brandt, W.; Dräger, B.; The functional divergence of short-chain dehydrogenases involved in tropinone reduction Plant J. 54, 388-401, (2008) DOI: 10.1111/j.1365-313X.2008.03422.x

Tropane alkaloids typically occur in the Solanaceae and are also found in Cochlearia officinalis , a member of the Brassicaceae. Tropinone reductases are key enzymes of tropane alkaloid metabolism. Two different tropinone reductases form one stereoisomeric product each, either tropine for esterified alkaloids or pseudotropine that is converted to calystegines. A cDNA sequence with similarity to known tropinone reductases (TR) was cloned from C. officinalis . The protein was expressed in Escherichia coli , and found to catalyze the reduction of tropinone. The enzyme is a member of the short‐chain dehydrogenase enzyme family and shows broad substrate specificity. Several synthetic ketones were accepted as substrates, with higher affinity and faster enzymatic turnover than observed for tropinone. C. officinalis TR produced both the isomeric alcohols tropine and pseudotropine from tropinone using NADPH + H+ as co‐substrate. Tropinone reductases of the Solanaceae, in contrast, are strictly stereospecific and form one tropane alcohol only. The Arabidopsis thaliana homologue of C. officinalis TR showed high sequence similarity, but did not reduce tropinone. A tyrosine residue was identified in the active site of C. officinalis TR that appeared responsible for binding and orientation of tropinone. Mutagenesis of the tyrosine residue yielded an active reductase, but with complete loss of TR activity. Thus C. officinalis TR presents an example of an enzyme with relaxed substrate specificity, like short‐chain dehydrogenases, that provides favorable preconditions for the evolution of novel functions in biosynthetic sequences.
Publikation

Bräuer, L.; Brandt, W.; Schulze, D.; Zakharova, S.; Wessjohann, L.; A Structural Model of the Membrane-Bound Aromatic Prenyltransferase UbiA from E. coli ChemBioChem 9, 982-992, (2008) DOI: 10.1002/cbic.200700575

We report the first reasonable model for the active site of the membrane‐bound aromatic prenyltransferase UbiA, derived from structural—not sequence—similarity to a terpene synthase, with the aid of threading, site‐directed mutagenesis, and substrate selectivities. The high similarity of the active fold of UbiA‐transferase to that of 5‐epi‐aristolochene synthase (Nictotiana tabacum ), despite a low homology, allows a hypothesis on a convergent evolution of these enzymes to be formed.
Publikation

Braga, A. L.; Paixão, M. W.; Westermann, B.; Schneider, P. H.; Wessjohann, L. A.; Acceleration of Arylzinc Formation and Its Enantioselective Addition to Aldehydes by Microwave Irradiation and Aziridine-2-methanol Catalysts J. Org. Chem. 73, 2879-2882, (2008) DOI: 10.1021/jo702413n

The formation and 2-amino alcohol catalyzed addition of arylzinc reagents from and with boronic acids, respectively, is drastically accelerated to a few minutes under microwave irradiation without loss of enantioselectivity (up to 98% ee). Of the amino acid derived catalysts tested, the conformationally restricted bulky substituted aziridine-2-methanols derived from serine show the best overall performance in the formation of diarylmethanols.
Publikation

Böttcher, C.; von Roepenack-Lahaye, E.; Schmidt, J.; Schmotz, C.; Neumann, S.; Scheel, D.; Clemens, S.; Metabolome Analysis of Biosynthetic Mutants Reveals a Diversity of Metabolic Changes and Allows Identification of a Large Number of New Compounds in Arabidopsis Plant Physiol. 147, 2107-2120, (2008) DOI: 10.1104/pp.108.117754

Metabolomics is facing a major challenge: the lack of knowledge about metabolites present in a given biological system. Thus, large-scale discovery of metabolites is considered an essential step toward a better understanding of plant metabolism. We show here that the application of a metabolomics approach generating structural information for the analysis of Arabidopsis (Arabidopsis thaliana) mutants allows the efficient cataloging of metabolites. Fifty-six percent of the features that showed significant differences in abundance between seeds of wild-type, transparent testa4, and transparent testa5 plants could be annotated. Seventy-five compounds were structurally characterized, 21 of which could be identified. About 40 compounds had not been known from Arabidopsis before. Also, the high-resolution analysis revealed an unanticipated expansion of metabolic conversions upstream of biosynthetic blocks. Deficiency in chalcone synthase results in the increased seed-specific biosynthesis of a range of phenolic choline esters. Similarly, a lack of chalcone isomerase activity leads to the accumulation of various naringenin chalcone derivatives. Furthermore, our data provide insight into the connection between p-coumaroyl-coenzyme A-dependent pathways. Lack of flavonoid biosynthesis results in elevated synthesis not only of p-coumarate-derived choline esters but also of sinapate-derived metabolites. However, sinapoylcholine is not the only accumulating end product. Instead, we observed specific and sophisticated changes in the complex pattern of sinapate derivatives.
Publikation

Bohn Rhoden, C. R.; Westermann, B.; Wessjohann, L.; One-Pot Multicomponent Synthesis of N-Substituted Tryptophan-Derived Diketopiperazines Synthesis 2008, 2077-2082, (2008) DOI: 10.1055/s-2008-1067112

A simple, rapid, one-pot multicomponent synthesis of tryptophan-derived diketopiperazines with variable side chains is presented. Microwave radiation gives comparable yields, but allows a significant decrease in reaction times.
Publikation

Baraza, L. D.; Joseph, C. C.; Munissi, J. J.; Nkunya, M. H.; Arnold, N.; Porzel, A.; Wessjohann, L.; Antifungal rosane diterpenes and other constituents of Hugonia castaneifolia Phytochemistry 69, 200-205, (2008) DOI: 10.1016/j.phytochem.2007.06.021

The rosane diterpenoids hugorosenone [3β-hydroxyrosa-1(10),15-dien-2-one], 18-hydroxyhugorosenone and 18-hydroxy-3-deoxyhugorosenone, and 12-hydroxy-13-methylpodocarpa-8,11,13-trien-3-one were isolated as antifungal constituents of H. castaneifolia Engl. root bark, together with the previously reported di-podocarpanoids hugonone A and hugonone B that were weakly active, and 1(10),15-rosadiene-2β,3β-diol (hugorosenol), 4α-methoxyhimachal-10-en-5β-ol (hugonianene B) and 2-hydroxyhenpentacont-2-enal, and the known compounds tetracosyl-(E)-ferrulate and caryophyllene oxide, all of which were inactive. Hugorosenone also exhibited activity against Anopheles gambiae mosquito larvae. Structural determination was achieved based on spectroscopic data.
Publikation

Ali, N. A. A.; Wurster, M.; Arnold, N.; Lindequist, U.; Wessjohann, L.; Essential Oil Composition from Oleogum Resin of Soqotraen Commiphora kua Rec. Nat. Prod. 2, 70-75, (2008)

The major constituents of the essential oil obtained by hydrodistillation from the oleogum resin of Commiphora kua Vollesen were identified by GC-MS. Sixteen constituents were detected from the essential oil, which constituted about (90.5%) of the total amount. Major constituents of the oil were α- cadinol (33.0%), g -cadinene (22.5%), d -cadinene (17.0%), isocaryophyllene (3.7%), allo-aromadendrene (2.8%), α-muurolene (2.7%), and α-humulene (2.4%). The Oil of Commiphora kua showed moderate antifungal activity against Cladosporium cucumerinum.
  • Die Leibniz-Gemeinschaft
  • Digitalisierung in der Landwirtschaft
  • Martin-Luther Universität Halle
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