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Secondary metabolites by chemical screening, 41 - Structure and biosynthesis of mutolide, a novel macrolide from a UV mutant of the fungus F-24 ' 707
No full textThe 14-membered macrolide, mutolide (1), was discovered by chemical screening of the culture broth of the fungus F-24'707y, obtained after UV mutagenesis of the wild type strain, which normally produces the spirobisnaphthalene cladospirone bisepoxide (2). The structure of 1 was established by detailed spectroscopic analysis, X-ray analysis and derivatisation. The biogenetic origin of the carbon skeleton and the hydroxy groups was verified by feeding sodium [1-C-13]acetate and O-18(2) to growing cultures of the fungus. Macrolide 1 is generated from acetate/malonate only. The unexpected change of the normal metabolite pattern of this strain is discussed, and proves the value of the OSMAC method
Secondary metabolites by chemical screening, 42 - Cladospirones B to I from Sphaeropsidales sp F-24 ' 707 by variation of culture conditions
No full textVariation of the culture conditions - static surface cultures in particular - of the fungus Sphaeropsidales sp. (strain F-24'707), which produces cladospirone bisepoxide (1), led to the isolation of eight new spirobisnaphthalenes - the cladospirones B to I (8-15) -together with seven known representatives of this class of secondary metabolites. Cladospirones C (9) and D (11) show antibiotic activity against bacteria and algae. The structures of cladospirone B (8) and E (12) were confirmed by X-ray structure analysis. Cladospirones C (9) and G to I (10, 14-15) represent new members of the spirobis-naphthalene family, thanks to their hydroxylation patterns. Moreover, they underline the extraordinary status of this interesting class of compounds as the most diverse secondary metabolites, allowing for their small number of carbon atoms, described to date. Almost all possible permutations of stereochemistry and oxygen substitution pattern on the C-10 skeleton are produced by different fungi
Biosynthesis of cladospirone bisepoxide, a member of the spirobisnaphthalene family
No full textThe biosynthesis of cladospirone bisepoxide (1) was investigated by feeding C-13-labeled acetate to growing cultures of the fungus Sphaeropsidales sp. (strain F-24'707). C-13 NMR spectral analysis demonstrated the polyketide origin of both naphthalene units. The origin of two epoxide oxygens was confirmed as from air by cultivation of the strain in an O-18(2)-enriched atmosphere. The [O-18]incorporation pattern into palmarumycin C-12 (11), the putative precursor of 1 led to the hypothesis that the carbonyl oxygen of 1 is derived from water by exchange of an oxygen atom. inhibition of the biosynthesis of 1 with tricyclazole, an inhibitor of the 1,8-dihydroxynaphthalene (DHN) melanin biosynthesis, confirmed the connection of both biosynthetic pathways
Secondary metabolites by chemical screening, 42 - Cladospirones B to I from Sphaeropsidales sp F-24 ' 707 by variation of culture conditions
No full textVariation of the culture conditions - static surface cultures in particular - of the fungus Sphaeropsidales sp. (strain F-24'707), which produces cladospirone bisepoxide (1), led to the isolation of eight new spirobisnaphthalenes - the cladospirones B to I (8-15) -together with seven known representatives of this class of secondary metabolites. Cladospirones C (9) and D (11) show antibiotic activity against bacteria and algae. The structures of cladospirone B (8) and E (12) were confirmed by X-ray structure analysis. Cladospirones C (9) and G to I (10, 14-15) represent new members of the spirobis-naphthalene family, thanks to their hydroxylation patterns. Moreover, they underline the extraordinary status of this interesting class of compounds as the most diverse secondary metabolites, allowing for their small number of carbon atoms, described to date. Almost all possible permutations of stereochemistry and oxygen substitution pattern on the C-10 skeleton are produced by different fungi
Secondary metabolites by chemical screening, 41 - Structure and biosynthesis of mutolide, a novel macrolide from a UV mutant of the fungus F-24 ' 707
No full textThe 14-membered macrolide, mutolide (1), was discovered by chemical screening of the culture broth of the fungus F-24'707y, obtained after UV mutagenesis of the wild type strain, which normally produces the spirobisnaphthalene cladospirone bisepoxide (2). The structure of 1 was established by detailed spectroscopic analysis, X-ray analysis and derivatisation. The biogenetic origin of the carbon skeleton and the hydroxy groups was verified by feeding sodium [1-C-13]acetate and O-18(2) to growing cultures of the fungus. Macrolide 1 is generated from acetate/malonate only. The unexpected change of the normal metabolite pattern of this strain is discussed, and proves the value of the OSMAC method
Structure and biosynthesis of kendomycin, a carbocyclic ansa-compound from Streptomyces
No full textKendomycin [(-)-TAN 2162] 1 was re-isolated from Streptomyces violaceoruber (strain 3844-33C) in the course of our chemical screening programme. The structure with the relative configuration only was confirmed by the X-ray analysis of 1. The absolute configuration of 1 was determined by using the advanced Mosher's ester method applied to kendomycin acetonide 2. The biosynthesis of 1 was performed using stable isotope labelling experiments. From the results it is assumed that a highly oxygenated benzoic acid, derived from (3,5-dihydroxyphenyl)acetic acid, serves as the starter unit of the aliphatic polyketide chain. The cyclisation generating the 18-membered ansa-bridge by the formation of a C-C bond might follow a new type of aldol condensation. 1 and 2 exhibit antibacterial activity and strong cytotoxicity against different tumor cell lines
Biosynthesis of kendomycin: origin of the oxygen atoms and further investigations
No full textThe origin of all oxygen atoms of the structurally unique polyketide antibiotic kendomycin 1 was confirmed by feeding [1-C-13,O-18(2)]acetate, [1-C-13,O-18(2)]propionate and O-18(2) to Streptomyces violaceoruber (strain 3844-33C) resulting in a more detailed insight into the biosynthesis of 1. Further information about the biosynthesis of the starter unit in which a chalcone synthase (CHS) must be involved was obtained from comparison of recent literature data with the requirements of the kendomycin biosynthesis. The incorporation of acetate into the methylmalonyl extender units reported previously was investigated by additional feeding [2-C-13]malonic acid and [1,4-C-13(2)]succinic acid to the strain. As a result, the coexistence of two independent pathways to methylmalonyl-CoA was demonstrated. Furthermore, feeding of N-acetylcysteamine and other thiols resulted in the formation of the new kendomycin derivatives 2 and 3 in good yields
Bacterial degradation of natural and synthetic rubber
No full textThe degradation of natural rubber (NR), synthetic poly(cis-1,4-isoprene) (SR), and cross-linked NR (latex gloves) by Gram-positive and Gram-negative bacteria was analyzed by weight loss, gel permeation chromatography, and determination of the protein content. Weight losses of 11-18% and an increase in protein up to 850 microg/mL after incubation of Nocardia sp. DSMZ43191, Streptomyces coelicolor, Streptomyces griseus, bacterial isolate 18a, Acinetobacter calcoaceticus, and Xanthomonas sp. with latex gloves as a carbon source indicated degradation of the polymer. An increase of protein up to 1250 microg/mL was obtained upon incubation of the bacteria with SR. No or only little weight losses and no increase in the protein content were found for nondegrading control strains such as Streptomyces lividans and Streptomyces exfoliatus and for mutants of degrading strains of S. coelicolor and S. griseus, which have been identified by their inability to produce clearing zones on opaque latex agar. Measurement of the average molecular weight of synthetic rubber before and after degradation showed a time-dependent shift to lower values for the degrading strains. Diketone derivates of oligo(cis-1,4-isoprene) were identified as metabolites of rubber degradation. An oxidative degradation pathway of poly(cis-1,4-isoprene) to acetyl-coenzymeA and propionyl-coenzymeA by beta-oxidation is suggested for bacterial degradation of isoprene rubber
Sphaerolone and dihydrosphaerolone, two bisnaphthyl-pigments from the fungus Sphaeropsidales sp. F-24′707
No full textTwo new bisnaphthalene compounds, sphaerolone (1) and dihydrosphaerolone (2), together with 2-hydroxyjuglone (9), were isolated from the culture broth of a Sphaeropsidales sp. (strain F-24'707) after inhibition of the regular proceeding 1,8-dihydroxynaphthalene (DHN) biosynthesis with tricyclazole. The structures of 1 and 2 were established by detailed spectroscopic analysis and present novel bisnaphthalenes. The biosynthetic origin of 1 and 2 as dimerization products of 1,3,8-trihydroxynaphthalene, an intermediate of the DHN biosynthesis, is discussed
UV mutagenesis and enzyme inhibitors as tools to elucidate the late biosynthesis of the spirobisnaphthalenes
No full textThe metabolite pattern of UV mutants of the spirobisnaphthalene producing fungus F-24'707 by TLC and HPLC analysis has been investigated. Mutants with differences in colony morphology or colour compared to the parent strain were isolated. Cultivation in shaking flasks and P flasks showed differences in the metabolite pattern of some of the strains. Furthermore, enzyme inhibitors were used to block the spirobisnaphthalene biosynthesis of the parent strain at different steps. Feeding of precursors and intermediates of cladospirone bisepoxide (15) led to a two-fold increase of the production of 15. From these data and preceding biosynthetic studies we deduced a general pathway for the biosynthesis of all spirobisnaphthalenes of the fungus F-24'707. This enables us to present the hypothesis that all bisnaphthalenes described so far are produced using a common pathway with only a few intermediates as central branching points. (C) 2000 Elsevier Science Ltd. All rights reserved
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