tailieunhanh - Báo cáo khoa học: Phenylalanine-independent biosynthesis of 1,3,5,8-tetrahydroxyxanthone A retrobiosynthetic NMR study with root cultures of Swertia chirata

Root cultures ofSwertia chirata(Gentianaceae) were grown with supplements of [1-13 C]glucose, [U-13 C6]glucose or [carboxy-13 C]shikimic acid. 1,3,5,8-Tetrahydroxyxanthone was isolated and analysed by quantitative NMR analysis. The observed isotopomer distribution shows that 1,3,5,8-tetrahydroxyxanthone is biosynthesized via a polyketide-type pathway. The starter unit, 3-hydroxybenzoyl-CoA, is obtained from an early shikimate pathway intermediate. Phenylalanine, cinnamic acid and benzoic acid were ruled out as intermediates | Eur. J. Biochem. 270 2950-2958 2003 FEBS 2003 doi Phenylalanine-independent biosynthesis of 1 3 5 8-tetrahydroxyxanthone A retrobiosynthetic NMR study with root cultures of Swertia chirata Chang-Zeng Wang1 Ulrich H. Maier1 Michael Keil2 Meinhart H. Zenk1 Adelbert Bacher3 Felix Rohdich3 and Wolfgang Eisenreich3 1 Biozentrum-Pharmazie Universitat Halle HalleịSaale Germany 2Boehringer Ingelheim Pharma KG Ingelheim Germany 3Lehrstuhl fur Organische Chemie und Biochemie Technische Universitdt Munchen Garching Germany Root cultures of Swertia chirata Gentianaceae were grown with supplements of 1-13C glucose U-13C6 glucose or carboxy-13C shikimic acid. 1 3 5 8-Tetrahydroxyxanthone was isolated and analysed by quantitative NMR analysis. The observed isotopomer distribution shows that 1 3 5 8-tetrahydroxyxanthone is biosynthesized via a polyketide-type pathway. The starter unit 3-hydroxybenzoyl-CoA is obtained from an early shikimate pathway intermediate. Phenylalanine cinnamic acid and benzoic acid were ruled out as intermediates. Keywords hydroxybenzoate isotope labelling NMR spectroscopy retrobiosynthesis xanthone. The shikimate pathway Fig. 1 supplies building blocks for a wide variety of plant metabolites via phenylalanine 7 such as lignin stilbenes and flavonoids or via early pathway intermediates as specific precursors. Differentiation between these alternatives is possible by retrobiosynthetic analysis using general 13C-labelled precursors . glucose reviewed in 1 . Using this approach we previously showed that the biosynthetic pathways of the tannic acid precursor gallic acid 8 and the bitter compound amarogentin 9 produced in Swertia chirata Gentianaceae branch off the shikimate pathway at a level before phenylpyruvate 6 Fig. 1 2 3 . We now exploit the retrobiosynthetic method to analyse the biosynthesis of a xanthone derivative. Xanthones are formed in at least 30 families of higher plants . Gentianaceae and Guttiferae 4 5 .

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