naphthoquinones and viomellein

Two undescribed viomellein derivatives, xanthoelegansin and spiroxanthoelegansin, were isolated together with clavatol, sitosteanone, vioxanthin, xanthomegnin, viomellein, rubrosulphin, rubrosulphin diacetate, viopurpurin , ochratoxin A, ochratoxin A methyl ester, ochratoxin B and ochratoxin β, from cultures of the marine sponge-associated fungus Aspergillus elegans KUFA0015. The structures of the undescribed compounds were established based on an extensive analysis of 1D and 2D NMR spectra as well as HRMS data. The structure of xanthoelegansin and the absolute configuration of its stereogenic carbons were confirmed by X-ray analysis. The change in conformation of xanthoelegansin was interpreted using quantum mechanical theoretical calculation data in combination with the observation of the change of the proton signals of the 1,3-dioxepine ring in 1HNMR spectra at varying temperatures. The mechanisms of the formation of xanthoelegansin and spiroxanthoelegansin from viomellein were proposed. Clavatol, sitosteanone, vioxanthin, xanthomegnin, viomellein, xanthoelegansin, rubrosulphin, rubrosulphin diacetate, ochratoxin A, ochratoxin A methyl ester, ochratoxin B and ochratoxin β were assayed for their antibacterial activity against reference strains and multidrug-resistant isolates from the environment. The tested compounds were also evaluated for their capacity to inhibit biofilm formation in the reference strains.

Topics: Animals; Anti-Bacterial Agents; Aspergillus; Benzopyrans; Indoles; Naphthoquinones; Nitro Compounds; Porifera

It is thought that fungi protect themselves from predation by the production of compounds that are toxic to soil-dwelling animals. Here, we show that a nontoxic pigment, the bis-naphthopyrone aurofusarin, protects Fusarium fungi from a wide range of animal predators. We find that springtails (primitive hexapods), woodlice (crustaceans), and mealworms (insects) prefer feeding on fungi with disrupted aurofusarin synthesis, and mealworms and springtails are repelled by wheat flour amended with the fungal bis-naphthopyrones aurofusarin, viomellein, or xanthomegnin. Predation stimulates aurofusarin synthesis in several Fusarium species and viomellein synthesis in Aspergillus ochraceus. Aurofusarin displays low toxicity in mealworms, springtails, isopods, Drosophila, and insect cells, contradicting the common view that fungal defence metabolites are toxic. Our results indicate that bis-naphthopyrones are defence compounds that protect filamentous ascomycetes from predators through a mechanism that does not involve toxicity.

Topics: Adaptation, Physiological; Animals; Arthropods; Aspergillus ochraceus; Food Preferences; Fusarium; Naphthoquinones; Pigments, Biological; Predatory Behavior

In the course of a search for anti-dormant mycobacterial substances from marine-derived microorganisms, viomellein (1) and xanthomegnin (2) were re- discovered from the active fraction of the culture of a marine-derived Aspergillus sp. together with rubrosulphin (3) and asteltoxin (4) on the guidance of bioassay-guided separation. In particular, compound 1 showed higher activity against the dormant than against actively growing Mycobacterium bovis BCG and weak activity against M smegmatis. Furthermore, evidence that compound 1 did not directly bind to plasmid DNA suggests its anti-mycobacterial activity differs from its direct chelating effect on the mycobacterial genome.

Topics: Antitubercular Agents; Aspergillus; Dimerization; Microbial Sensitivity Tests; Mycobacterium; Naphthoquinones; Seawater

Penicillium freii (Lund and Frisvad 1994) mutants deficient in the synthesis of xanthomegnin were isolated. In vitro translated mRNA populations from selected radiation induced mutants and naturally occurring P. freii strains not able to produce xanthomegnin were examined by 2-dimensional polyacrylamide gel electrophoresis (2D-PAGE). Specific translation products were absent in mutants and natural isolates unable to produce xanthomegnin metabolites. One mutant (TSM 73) did not produce several of these translation products, indicating that a mutation in a regulatory gene involved in xanthomegnin production had occurred.

Topics: Electrophoresis, Gel, Two-Dimensional; Fungal Proteins; Gene Expression Regulation, Fungal; Genetic Variation; Hydroxyquinolines; Mutagenesis; Naphthoquinones; Penicillium; Protein Biosynthesis; RNA, Messenger; Xanthine; Xanthines

Wheat seed was adjusted to 18, 20, 22, 24 and 26% moisture content (m.c.), and stored for 240 days at 4 or 10 degrees C following inoculation with a strain of Penicillium viridicatum producing the toxins, xanthomegnin (XA), viomellein (VIO), and brevianamide A (BA). Wheat kernels were not sterilized before inoculation. The concentration of ergosterol (ERG), a chemical indicator of fungal biomass, remained constant at 18% m.c./4 degrees C, but increased under the other conditions. The time before a detectable increase of ERG concentration was higher and the rate of ERG production lower with decreasing moisture content and temperature. XA and BA were produced at both temperatures at 20-26% m.c., VIO was produced at 22-26% m.c./4 degrees C and 20-26% m.c./10 degrees C. The results suggest or indicate that the onset of XA, VIO and BA production (detection limits: 10, 15, and 0.1 micrograms/kg, respectively) coincided with the onset of ERG production. Maximum toxin contents were lower with decreasing moisture content at both temperatures, but were similar at 4 and 10 degrees C at 22-26% m.c. It is concluded that wheat contaminated with P. viridicatum should not be stored beyond the onset of ergosterol production; maximum storage periods are recommended.

Topics: Alkaloids; Cold Temperature; Ergosterol; Food Microbiology; Food Preservation; Mycotoxins; Naphthoquinones; Penicillium; Pigments, Biological; Piperazines; Refrigeration; Seeds; Spiro Compounds; Triticum

In a batch of barley associated with field cases of mycotoxic porcine nephropathy and containing ochratoxin A and citrinin, the mycoflora were isolated by parallel incubation at 10 and 25 degrees C. Subsequently, the isolated cultures were checked for production of nephrotoxins (xanthomegnin, viomellein, ochratoxin, and citrinin). The nephrotoxin producers, all isolated by incubation at 10 degrees C, were comprised of one culture of Penicillium viridicatum, five cultures of Penicillium cyclopium, and one culture of Penicillium crustosum, all producing xanthomegnin and viomellein. One culture of P. cyclopium produced citrinin. Viomellein was detected in the barley at a concentration of approximately 1 mg/kg. The method of analysis for xanthomegnin and viomellein included extraction with chloroform, partitioning in hexane-acetone, and thin-layer chromatographic separation and identification. The identity of the xanthomegnin and viomellein produced by the isolated fungi and of viomellein detected in the barley was supported by infrared spectroscopy. This is the first report of viomellein as a natural contaminant of foodstuffs.

Topics: Animals; Food Contamination; Food Microbiology; Hordeum; Kidney Diseases; Mycotoxins; Naphthoquinones; Penicillium; Quinones; Swine; Swine Diseases

A medium, pentachloronitrobenzene-rose bengal-yeast extract-sucrose agar (PRYES), for the isolation of moulds occurring during storage of cereals has been developed and compared with other selective media. The basal medium is yeast extract agar containing 15% sucrose (w/v). In addition to the sucrose content further selective measures include the addition of antibacterial antibiotics chloramphenicol and chlortetracycline (50 mg/l), the fungicides rose bengal (25 mg/l each), and pentachloronitrobenzene (1 g/l) and a low incubation temperature (20 degrees C). Members of the Mucorales were completely inhibited, and fast-growing species of other moulds were slightly inhibited, allowing important storage moulds to develop. The important ochratoxin A and citrinin-producing Penicillium viridicatum group II was indicated by a typical violet brown reverse on PRYES. Producers of xanthomegnin and viomellein (P. viridicatum group I and P. aurantiogriseum) were indicated on PRYES by their yellow reverse and obverse colours. The medium was used for screening 40 samples of barley, and moulds with the characteristic colours were all identified as the species mentioned above.

Topics: Citrinin; Culture Media; Edible Grain; Food Microbiology; Hordeum; Mycotoxins; Naphthoquinones; Ochratoxins; Penicillium; Triticum

Fungal isolates from legumes were cultured on rice and examined for production of the toxic mold metabolites xanthomegnin and viomellein. Six of 14 Aspergillus ochraceus isolates produced from 0.3 to 1.3 mg of xanthomegnin per g and 0.1 to 1.0 mg of viomellein per g. One of nine isolates of Penicillium cyclopium produced 0.1 mg of xanthomegnin per g and 0.06 mg of viomellein per g. Three of nine P. viridicatum isolates produced from 0.4 to 1.6 mg of xanthomegnin per g and 0.2 to 0.4 mg of viomellein per g. This is the first report of xanthomegnin and viomellein production by A. ochraeus and P. cyclopium.

Topics: Aspergillus; Culture Media; Fabaceae; Food Microbiology; Mycotoxins; Naphthoquinones; Oryza; Penicillium; Plants, Medicinal; Species Specificity

By using thin-layer chromatography and infrared spectroscopy, xanthomegnin and viomellein have been isolated and identified from species of the Aspergillus ochraceus group. A correlation was established between the occurrence of these fungal quinones in the fungal cultural products and the ability of these products to induce mycotoxicosis in mice. In addition, a method was employed to estimate the amount of xanthomegnin and viomellein produced by the fungi.

Topics: Animals; Aspergillus; Chromatography, Thin Layer; Female; Male; Mice; Mycotoxins; Naphthoquinones; Species Specificity; Spectrophotometry, Infrared

Topics: Animals; Biotransformation; Chemical and Drug Induced Liver Injury; Diet; Kidney; Liver; Male; Mice; Mycotoxins; Naphthoquinones; Penicillium; Pigments, Biological