The biosynthesis of fungal metabolites. Part VI. Structures and biosynthesis of some minor metabolites from variant strains of Aspergillus variecolor

Chexal, Kuldip K.; Holker, J. S. E.; Simpson, Thomas J.

doi:10.1039/p19750000549

Cited by 34 publications

(48 citation statements)

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“…Subsequent hydrolysis of 4 gave tajixanthone hydrate with spectroscopic properties, including optical rotation, in agreement with those previously described. 21,22 Thus, the structure and relative stereochemistry of 4 were confirmed. Furthermore, the absolute configuration (depicted in Chart 1) could be established, H-1′ 2′ 5, 3′ H-2′ 1′, 3′ 6, 3′ 5, 3′, 4′ 3′, 4′ H-3′ 2′, 4′ 1′, 2′, 6′ 1′, 2′, 6′, 2′′ H-4′ 3′, 5′, OH 2′, 5′ 2′, 5′, 3′′ H-5′ 4′, 6′, OH 4′, 7′ 4′, 7′, 3′′ H-6′ 5′, 7′ 3′, 7′ 3′, 7′, 2′′ H 3-7′ 6′ 5′, 6′ OCH3 2 OCH2-C-1 OH 1, 2, 6 H3-2′′ 3′, 6′…”

Section: Resultsmentioning

confidence: 76%

“…21 The HRMS of varitriol (1) indicated a C 15 H 20 O 5 molecular formula, corresponding to six elements of unsaturation. The main feature of the IR spectrum was a very strong absorption band centered at 3338 cm -1 , suggesting the presence of more than one hydroxyl group.…”

Section: Resultsmentioning

confidence: 99%

“…22 [R] 25 D -71.5°, c 2.3, CHCl3); 1 H and 13 C NMR spectra matched those previously described. 21,22 Triacetylvaritriol ( …”

Section: Methodsmentioning

confidence: 99%

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Bioactive Metabolites from a Marine-Derived Strain of the Fungus Emericella variecolor

et al. 2002

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From a marine-derived strain of the fungus Emericella variecolor, varitriol (1), varioxirane (2), dihydroterrein (3), and varixanthone (4), besides the known mold metabolites ergosterol, terrein, shamixanthone, and tajixanthone hydrate, were identified. The chemical structures of 1-4 were established by means of spectroscopic techniques and some chemical transformations. In the NCI's 60-cell panel, varitriol (1) displayed increased potency toward selected renal, CNS, and breast cancer cell lines. Varixanthone (4) showed antimicrobial activity.Recently, increased interest in the chemistry of fungi isolated from the marine environment has been documented. 1 Marine fungi are interesting organisms from an ecological point of view, because they are serious pathogens in the marine environment. 2 Furthermore, since many can be cultured, they represent an important biomedical resource. During our studies on the chemistry and biology of fungi, 3,4 we have investigated a marine strain 5 (named M75-2) of the fungus Emericella variecolor, isolated from a sponge collected in Venezuelan waters of the Caribbean Sea. 6 E. variecolor Berk and Br. is the perfect state of Aspergillus variecolor (Berk and Br.) Thom and Raper. 7 From different terrestrial strains of A. variecolor terrein, 8 2-methoxy-6-(3,4-dihydroxyhepta-1,5-dienyl)benzyl alcohol, 9 4,7-dimethoxy-5-methylcoumarin, 10 a dihydroisocoumarin, 11 and two sesterterpenoids (variecolin 12 and astellatol 13 ), as well as numerous xanthones 14 and meroterpenoids 15 of mixed polyketide and terpenoid origins, have been isolated. Moreover, in a terrestrial strain of E. variecolor, asteltoxin has been found. 16,17 This report deals with the chemical analysis and biological screening of the metabolites from the first marine strain of E. variecolor. Results and DiscussionFrom a static culture of the fungus the new compounds 1-4 (Chart 1) were identified, in addition to the known mold metabolites ergosterol, 18 terrein, 19 shamixanthone, 20 and tajixanthone hydrate. 21

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Section: Resultsmentioning

confidence: 76%

Section: Resultsmentioning

confidence: 99%

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Bioactive Metabolites from a Marine-Derived Strain of the Fungus Emericella variecolor

et al. 2002

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“…Based on their physical and spectral properties, compounds 1, 2, and 5 from strain CLS12 (Fig. 4) were identified as being the polyketides shamixanthone (8), emericellin (26,27), and dehydroaustinol (20,39). Spectral data and comparisons with authentic samples showed that compounds 3, 4, and 6 were ergosterol, ergosterol peroxide (59), and cerevisterol (58).…”

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confidence: 99%

“…Spectral data and comparisons with authentic samples showed that compounds 3, 4, and 6 were ergosterol, ergosterol peroxide (59), and cerevisterol (58). Shamixanthone is a moderately cytotoxic molecule first isolated from Aspergillus variecolor (8) but not reported previously in A. nidulans.…”

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Phosphopantetheinyl Transferase CfwA/NpgA Is Required for Aspergillus nidulans Secondary Metabolism and Asexual Development

et al. 2007

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Polyketide synthases (PKSs) and/or nonribosomal peptide synthetases (NRPSs) are central components of secondary metabolism in bacteria, plants, and fungi. In filamentous fungi, diverse PKSs and NRPSs participate in the biosynthesis of secondary metabolites such as pigments, antibiotics, siderophores, and mycotoxins. However, many secondary metabolites as well as the enzymes involved in their production are yet to be discovered. Both PKSs and NRPSs require activation by enzyme members of the 4-phosphopantetheinyl transferase (PPTase) family. Here, we report the isolation and characterization of Aspergillus nidulans strains carrying conditional (cfwA2) and null (⌬cfwA) mutant alleles of the cfwA gene, encoding an essential PPTase. We identify the polyketides shamixanthone, emericellin, and dehydroaustinol as well as the sterols ergosterol, peroxiergosterol, and cerevisterol in extracts from A. nidulans large-scale cultures. The PPTase CfwA/NpgA was required for the production of these polyketide compounds but dispensable for ergosterol and cerevisterol and for fatty acid biosynthesis. The asexual sporulation defects of cfwA, ⌬fluG, and ⌬tmpA mutants were not rescued by the cfwA-dependent compounds identified here. However, a cfwA2 mutation enhanced the sporulation defects of both ⌬tmpA and ⌬fluG single mutants, suggesting that unidentified CfwA-dependent PKSs and/or NRPSs are involved in the production of hitherto-unknown compounds required for sporulation. Our results expand the number of known and predicted secondary metabolites requiring CfwA/NpgA for their biosynthesis and, together with the phylogenetic analysis of fungal PPTases, suggest that a single PPTase is responsible for the activation of all PKSs and NRPSs in A. nidulans.Filamentous fungi represent a rich and diverse source of bioactive compounds derived from secondary metabolism. Indeed, many positive and negative effects that fungi have on human activity are mediated by secondary metabolites such as antibiotics and other pharmaceutical drugs, mycotoxins, or pathogen virulence factors (22, 30, 54-56, 60, 66). In contrast to primary metabolism, common to most living organisms, secondary metabolism is not essential for the immediate survival of the producing organism. Furthermore, different taxonomic groups produce different types of secondary metabolites.Despite their large chemical diversity, secondary metabolites can be grouped according to their primary metabolism precursors. Acetyl coenzyme A, shikimate, and amino acids are major secondary metabolite building units. Acetyl coenzyme A is used to produce terpenoids, steroids, carotenoids, and polyketides.

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Genetic and Biosynthetic Studies of the Fungal Prenylated Xanthone Shamixanthone and Related Metabolites in Aspergillus spp. Revisited

Simpson

2012

ChemBioChem

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Biosynthetic genes for the prenylated xanthone shamixanthone have been identified in the Aspergillus nidulans genome; based on assignment of putative functions from sequence analyses and selected gene deletions, a pathway was proposed leading from the anthraquinone emodin via the benzophenone carboxylic acid monodictyphenone and the xanthone emericellin to shamixanthone. Several aspects of this proposed pathway are inconsistent with previously identified biosynthetic intermediates: the anthraquinone chrysophanol and the benzophenone aldehyde derivatives arugosins F and A/B, isotopic labelling studies and chemical precedents. A new pathway is presented that provides a full rationale for the results of the gene deletion studies and reconciles them with previous biosynthetic results, and is in accord with established chemical and biosynthetic mechanisms. The importance of interpreting genetic information in terms of established biosynthetic events is discussed.

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The biosynthesis of fungal metabolites. Part VI. Structures and biosynthesis of some minor metabolites from variant strains of Aspergillus variecolor

Cited by 34 publications

References 0 publications

Bioactive Metabolites from a Marine-Derived Strain of the Fungus Emericella variecolor

Bioactive Metabolites from a Marine-Derived Strain of the Fungus Emericella variecolor

Phosphopantetheinyl Transferase CfwA/NpgA Is Required for Aspergillus nidulans Secondary Metabolism and Asexual Development

Genetic and Biosynthetic Studies of the Fungal Prenylated Xanthone Shamixanthone and Related Metabolites in Aspergillus spp. Revisited

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