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Publikationen - Natur- und Wirkstoffchemie

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Publikation

Lusebrink, I.; Dettner, K.; Schierling, A.; Müller, T.; Daolio, C.; Schneider, B.; Schmidt, J.; Seifert, K.; New Pyridine Alkaloids from Rove Beetles of the Genus Stenus (Coleoptera: Staphylinidae) Z. Naturforsch. C 64, 271-278, (2009) DOI: 10.1515/znc-2009-3-420

Three new pyridine alkaloids were detected in the pygidial glands of some Stenus species. The chemotaxonomic significance of the occurrence of these alkaloids and stenusine in different Stenus species is discussed. The antimicrobial properties of (Z)- and (E)-3-(2- methyl-1-butenyl)-pyridine and the deterrent activities of stenusine and norstenusine were investigated.
Publikation

Schliemann, W.; Schneider, B.; Wray, V.; Schmidt, J.; Nimtz, M.; Porzel, A.; Böhm, H.; Flavonols and an indole alkaloid skeleton bearing identical acylated glycosidic groups from yellow petals of Papaver nudicaule Phytochemistry 67, 191-201, (2006) DOI: 10.1016/j.phytochem.2005.11.002

From yellow petals of Iceland poppy, besides the known flavonoid gossypitrin, seven kaempferol derivatives were isolated. In addition to kaempferol 3-O-β-sophoroside and kaempferol 3-O-β-sophoroside-7-O-β-glucoside, known from other plants, the mono- and dimalonyl conjugates of the latter were identified by MS and NMR spectroscopy. Structure analyses of a set of co-occurring pigments, the nudicaulins, revealed that they have the identical acylated glycoside moieties attached to a pentacyclic indole alkaloid skeleton for which the structure of 19-(4-hydroxyphenyl)-10H-1,10-ethenochromeno[2,3-b]indole-6,8,18-triol was deduced from MS and NMR as well as chemical and chiroptical methods.
Publikation

Eckermann, C.; Schröder, G.; Eckermann, S.; Strack, D.; Schmidt, J.; Schneider, B.; Schröder, J.; Stilbenecarboxylate biosynthesis: a new function in the family of chalcone synthase-related proteins Phytochemistry 62, 271-286, (2003) DOI: 10.1016/S0031-9422(02)00554-X

Chalcone (CHS), stilbene (STS) synthases, and related proteins are key enzymes in the biosynthesis of many secondary plant products. Precursor feeding studies and mechanistic rationalization suggest that stilbenecarboxylates might also be synthesized by plant type III polyketide synthases; however, the enzyme activity leading to retention of the carboxyl moiety in a stilbene backbone has not yet been demonstrated. Hydrangea macrophylla L. (Garden Hortensia) contains stilbenecarboxylates (hydrangeic acid and lunularic acid) that are derived from 4-coumaroyl and dihydro-4-coumaroyl starter residues, respectively. We used homology-based techniques to clone CHS-related sequences, and the enzyme functions were investigated with recombinant proteins. Sequences for two proteins were obtained. One was identified as CHS. The other shared 65–70% identity with CHSs and other family members. The purified recombinant protein had stilbenecarboxylate synthase (STCS) activity with dihydro-4-coumaroyl-CoA, but not with 4-coumaroyl-CoA or other substrates. We propose that the enzyme is involved in the biosynthesis of lunularic acid. It is the first example of a STS-type reaction that does not lose the terminal carboxyl group during the ring folding to the end product. Comparisons with CHS, STS, and a pyrone synthase showed that it is the only enzyme exerting a tight control over decarboxylation reactions. The protein contains unusual residues in positions highly conserved in other CHS-related proteins, and mutagenesis studies suggest that they are important for the structure or/and the catalytic activity. The formation of the natural products in vivo requires a reducing step, and we discuss the possibility that the absence of a reductase in the in vitro reactions may be responsible for the failure to obtain stilbenecarboxylates from substrates like 4-coumaroyl-CoA.Hydrangea macrophylla (Garden Hortensia) encodes a type III polyketide synthase synthesizing the stilbenecarboxylate backbone which is the basis for the biosynthesis of many secondary products in liverworts and in higher plants.
Publikation

Berlich, M.; Menge, S.; Bruns, I.; Schmidt, J.; Schneider, B.; Krauss, G.-J.; Coumarins give misleading absorbance with Ellman’s reagent suggestive of thiol conjugates Analyst 127, 333-336, (2002) DOI: 10.1039/B110988J

In the course of a screening for phytochelatins in cadmium-exposed bryophytes in the terrestrial mosses Polytrichum formosum and Atrichum undulatum we detected compounds with absorption properties and retention times similar to phytochelatins when applying the commonly used standard method RP-HPLC and post-column derivatization with thiol-specific DTNB (Ellman) reagent. Moreover, as with phytochelatins known in other plants, the concentrations of these compounds increased slightly after Cd stress. The concentration of the precursor glutathione (γ-ECG), however, increased in the presence of Cd. In order to verify the identity of these putative phytochelatins we performed LC-ESI-MS analyses as well as 1H NMR on extracts from P. formosum and A. undulatum. Spectroscopic investigations indicated that the detected compounds were neither phytochelatins nor other thiol compounds. From the results of HPLC-1H NMR and mass spectrometry we concluded that at least one of these substances was a coumarin, probably a 5,8-dihydroxy-7-methoxycoumarin-5-β-glucopyranoside, which has already been described for A. undulatum and P. formosum. The results of our investigations prove that under the basic pH conditions essential for the Ellman test for thiol compounds, coumarins show comparable UV/VIS absorption properties. Therefore, a positive post-column Ellman reaction cannot unambiguously prove the presence of thiol-containing compounds in plants.
Publikation

Winter, J.; Schneider, B.; Meyenburg, S.; Strack, D.; Adam, G.; Monitoring brassinosteroid biosynthetic enzymes by fluorescent tagging and HPLC analysis of their substrates and products Phytochemistry 51, 237-242, (1999) DOI: 10.1016/S0031-9422(98)00760-2

Both the vicinal side chain hydroxyl groups and the 6-oxo function of brassinosteroids were modified by fluorescence tagging. Dansylaminophenylboronic acid was used as a derivatizing agent to form fluorescent esters of brassinosteroids containing a side-chain cis-diol structure. 6-Oxo type brassinosteroids were derivatized by means of dansylhydrazine. The modified brassinosteroids, as far as possible derivatized both at the diol and the oxo group, were separated by HPLC and the optimal emission wavelength was determined. By this approach almost all brassinosteroids, including biosynthetic precursors, were susceptible to highly sensitive analysis in the fmol range. This method has been verified as an analytical tool to determine brassinosteroids in cell culture extracts and to monitor brassinosteroid biosynthetic enzymes. 24-Epibrassinolide has been detected in tomato cell suspension cultures. Several steps of brassinosteroid biosynthesis, including the Baeyer–Villiger oxidation of 24-epicastasterone to give 24-epibrassinolide, were monitored in vitro with protein preparations of the same cell culture line.
Bücher und Buchkapitel

Adam, G.; Schmidt, J.; Schneider, B.; Brassinosteroids Fortschritte der Chemie organischer Naturstoffe / Progress in the Chemistry of Organic Natural Products 78, 1-46, (1999) ISBN: 978-3-7091-6394-8 DOI: 10.1007/978-3-7091-6394-8_1

It was in 1979 when GROVE et al. isolated from pollen of rape (Brassica napus) a highly active plant growth promoter, named it brassinolide and elucidated its structure as (22R,23R,24S)-2α,3α, 22,23-tetrahydroxy-24-methyl-B-homo-6a-oxa-5α-cholestan-6-one (1) by spectroscopic methods including X-ray analysis (1). The original structural features of this compound and its unique high biological activity at very low concentrations stimulated intense research activities in many laboratories. Such efforts were directed towards the search for similar compounds in the plant kingdom, their chemical synthesis, biochemistry and biological mode of action leading up to their practical application in agriculture and horticulture. As a result of this interdisciplinary and rapidly processing research, brassinosteroids can nowadays be regarded as a new class of plant hormones with ubiquitous occurrence in the plant kingdom. Especially, recent molecular biological studies demonstrated their essential role for normal plant growth and development. A series of reviews have been published (2–11). Whereas the first book on brassinosteroid research covers developments up to 1990 (12), two up-to-date publications about this topic have appeared very recently (13, 14). The present article covers the literature up to December 1998 with special consideration of phytochemical, analytical and biochemical aspects.
Publikation

Kolbe, A.; Schneider, B.; Porzel, A.; Adam, G.; Metabolic inversion of the 3-hydroxy function of brassinosteroids Phytochemistry 48, 467-470, (1998) DOI: 10.1016/S0031-9422(98)00037-5

Exogenously applied 3-dehydro-24-epi-teasterone is transformed by cell suspension cultures of Lycopersicon esculentum to give the metabolites 24-epi-teasterone and 24-epi-typhasterol in about equal but low quantities. The major portion of 24-epi-teasterone was found as carbohydrate conjugates while 24-epi-typhasterol occurred in free form, indicating significant influence of glycosidation on the equilibrium between both compounds. The importance of these conjugation processes for the regulation of the brassinosteroid biosynthesis is discussed.In tomato cell cultures, 3-dehydro-24-epi-teasterone is transformed both to 24-epi-teasterone and 24-epi-typhasterol. The ratio between both epimers is regulated by glycosidation in 3β-position
Publikation

Winter, J.; Schneider, B.; Strack, D.; Adam, G.; Role of a cytochrome P450-dependent monooxygenase in the hydroxylation of 24-epi-brassinolide Phytochemistry 45, 233-237, (1997) DOI: 10.1016/S0031-9422(96)00827-8

24-epi-Brassinolide, exogenously applied to cell suspension cultures of Lycopersicon esculentum is hydroxylated at C-25 and C-26, respectively, followed by glucosylation of the newly formed hydroxyl group. Treatment of the cell cultures with the specific cytochrome P450 inhibitors, clotrimazole and ketoconazole, resulted in a strong decrease of only the C-25 hydroxylation, whereas hydroxylation at C-26 was not affected. The common cytochrome P450 inducers, ethanol, MnCl2, phenobarbital, pregnenolone 16α-carbonitrile or clofibrate, did not induce hydroxylation activity at C-25 or at C-26. In addition, substrate analogues (22S,23S-homobrassinolide, 24-epi-castasterone, ecdysone, and 20-OH-ecdysone) were not accepted. Only application of 24-epi-brassinolide and brassinolide resulted in an increased activity of both the C-25- and C-26-hydroxylases. For further examination of the molecular level of this inducing effect, the influence of the protein biosynthesis inhibitor cycloheximide has been studied. Thus, increase of both hydroxylase activities is obviously based on gene expression by action of the substrates, 24-epi-brassinolide and brassinolide.
Publikation

Kolbe, A.; Porzel, A.; Schneider, B.; Adam, G.; Diglycosidic metabolites of 24-epi-teasterone in cell suspension cultures of Lycopersicon esculentum L. Phytochemistry 46, 1019-1022, (1997) DOI: 10.1016/S0031-9422(97)00390-7

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Bücher und Buchkapitel

Adam, G.; Porzel, A.; Schmidt, J.; Schneider, B.; Voigt, B.; New Developments in Brassinosteroid Research Stud. Nat. Prod. Chem. 18, 495-549, (1995) DOI: 10.1016/S1572-5995(96)80033-0

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