Isolation and identification of xanthomegnin, viomellein, rubrosulphin, and viopurpurin as metabolites of penicillium viridicatum

The Secondary Metabolites and Biosynthetic Diversity From Aspergillus ochraceus

Aspergillus ochraceus, generally known as a food spoilage fungus, is the representative species in Aspergillus section Circumdati. A. ochraceus strains are widely distributed in nature, and usually isolated from cereal, coffee, fruit, and beverage. Increasing cases suggest A. ochraceus acts as human and animal pathogens due to producing the mycotoxins. However, in terms of benefits to mankind, A. ochraceus is the potential source of industrial enzymes, and has excellent capability to produce diverse structural products, including polyketides, nonribosomal peptides, diketopiperazine alkaloids, benzodiazepine alkaloids, pyrazines, bis-indolyl benzenoids, nitrobenzoyl sesquiterpenoids, and steroids. This review outlines recent discovery, chemical structure, biosynthetic pathway, and bio-activity of the natural compounds from A. ochraceus.

Fungal quinones: diversity, producers, and applications of quinones from Aspergillus, Penicillium, Talaromyces, Fusarium, and Arthrinium

Quinones represent an important group of highly structurally diverse, mainly polyketide-derived secondary metabolites widely distributed among filamentous fungi. Many quinones have been reported to have important biological functions such as inhibition of bacteria or repression of the immune response in insects. Other quinones, such as ubiquinones are known to be essential molecules in cellular respiration, and many quinones are known to protect their producing organisms from exposure to sunlight. Most recently, quinones have also attracted a lot of industrial interest since their electron-donating and -accepting properties make them good candidates as electrolytes in redox flow batteries, like their often highly conjugated double bond systems make them attractive as pigments. On an industrial level, quinones are mainly synthesized from raw components in coal tar. However, the possibility of producing quinones by fungal cultivation has great prospects since fungi can often be grown in industrially scaled bioreactors, producing valuable metabolites on cheap substrates. In order to give a better overview of the secondary metabolite quinones produced by and shared between various fungi, mainly belonging to the genera Aspergillus, Penicillium, Talaromyces, Fusarium, and Arthrinium, this review categorizes quinones into families such as emodins, fumigatins, sorbicillinoids, yanuthones, and xanthomegnins, depending on structural similarities and information about the biosynthetic pathway from which they are derived, whenever applicable. The production of these quinone families is compared between the different genera, based on recently revised taxonomy. KEY POINTS: • Quinones represent an important group of secondary metabolites widely distributed in important fungal genera such as Aspergillus, Penicillium, Talaromyces, Fusarium, and Arthrinium. • Quinones are of industrial interest and can be used in pharmacology, as colorants and pigments, and as electrolytes in redox flow batteries. • Quinones are grouped into families and compared between genera according to the revised taxonomy.

Fungi as a Potential Source of Pigments: Harnessing Filamentous Fungi

The growing concern over the harmful effects of synthetic colorants on both the consumer and the environment has raised a strong interest in natural coloring alternatives. As a result the worldwide demand for colorants of natural origin is rapidly increasing in the food, cosmetic and textile sectors. Natural colorants have the capacity to be used for a variety of industrial applications, for instance, as dyes for textile and non-textile substrates such as leather, paper, within paints and coatings, in cosmetics, and in food additives. Currently, pigments and colorants produced through plants and microbes are the primary source exploited by modern industries. Among the other non-conventional sources, filamentous fungi particularly ascomycetous and basidiomycetous fungi (mushrooms), and lichens (symbiotic association of a fungus with a green alga or cyanobacterium) are known to produce an extraordinary range of colors including several chemical classes of pigments such as melanins, azaphilones, flavins, phenazines, and quinines. This review seeks to emphasize the opportunity afforded by pigments naturally found in fungi as a viable green alternative to current sources. This review presents a comprehensive discussion on the capacity of fungal resources such as endophytes, halophytes, and fungi obtained from a range or sources such as soil, sediments, mangroves, and marine environments. A key driver of the interest in fungi as a source of pigments stems from environmental factors and discussion here will extend on the advancement of greener extraction techniques used for the extraction of intracellular and extracellular pigments. The search for compounds of interest requires a multidisciplinary approach and techniques such as metabolomics, metabolic engineering and biotechnological approaches that have potential to deal with various challenges faced by pigment industry.

Influence of the cultivation medium and pH on the pigmentation of Trichophyton rubrum

Trichophyton rubrum is a human pathogenic fungus. As a dermatophyte it causes athlete's foot, fungal infection of nails, jock itch and ringworm. The pigmentation of T. rubrum is variable and can range from white or yellow to wine-red. We demonstrate that the pigmentation is strongly influenced by pH. Under alkaline conditions, T. rubrum has a red pigmentation, whereas at acid conditions, T. rubrum has a yellow pigmentation. Moreover, the color change immediately from yellow to red by adding NaOH and reverse immediately from red to yellow by adding HCl. We suggest that the chemical compound Xanthomegnin is responsible for red as well for yellow pigmentation in T. rubrum. To figure out, why T. rubrum has red pigmentation on Trichophyton medium, adjust to alkaline, but not on Synthetic-Complete medium, also adjusted to alkaline, we measure the pH of liquid media, adjusted to pH 3.5, 6 and 8, over a period of four weeks. The pH of both cultivation media changes significantly, with a maximum of five pH levels. Whereas the Trichophyton medium, initially adjusted to pH 8, stays alkaline, the pH of the Synthetic-Complete medium drops to acid conditions. The acidification of the SC medium and the alkalization of the Trichophyton medium explains the different pigment color of the T. rubrum colonies.

Anti-dormant Mycobacterial Activity of Viomellein and Xanthomegnin, Naphthoquinone Dimers Produced by Marine-derived Aspergillus sp

In the course of a search for anti-dormant mycobacterial substances from marine-derived microorganisms, viomellein (1) and xanthomegnin (2) were rediscovered 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.

Naphthopyranones--isolation, bioactivity, biosynthesis and synthesis

The 1H-naphtho[2,3-c]pyran-1-one (naphthopyranone) moiety forms the structural framework of a group of secondary metabolites that have been isolated from a range of organisms including fungi, bacteria, lichen and plants. This review documents the known naturally occurring naphthopyranones - their isolation, biosynthesis and biological activity. A survey of methods reported for the synthesis of naphthopyranone natural products is presented.

Detection of xanthomegnin in epidermal materials infected with Trichophyton rubrum

Xanthomegnin, a mutagenic mycotoxin best known as an agent of nephropathy and death in farm animals exposed to food-borne Penicillium and Aspergillus fungi, was first isolated about 35 y ago as a diffusing pigment from cultures of the dermatophyte, Trichophyton megninii. This study investigates the production of xanthomegnin by the most common dermatophytic species, Trichophyton rubrum, both in dermatologic nail specimens and in culture. In view of the labile nature of xanthomegnin, a chromatographic procedure was developed to allow high-performance liquid chromatography analysis within 1 h of sample extraction. In cultures, Tricho- phyton rubrum produced xanthomegnin as a major pigment that appears to give the culture its characteristic red colony reverse. Xanthomegnin was also repeatedly extracted from human nail and skin material infected by Trichophyton rubrum. The level of xanthomegnin present, however, varied among the clinical samples studied. Xanthomegnin was not detected in uninfected nails. These results show that patients with Trichophyton rubrum infections may be exposed to xanthomegnin, although the consequences of such an exposure are not currently known.

Naphthoquinone metabolites of the fungi

Structures and physico-chemical properties of 100 naphthoquinone metabolites produced by filamentous fungi are reviewed. The conditions of pigment formation, biogenesis and the mechanism of biosynthesis of pigments by fungi are described. Sixty-three fungi cultures able to produce naphthoquinone are listed. The biological activities of the main pigments and the mechanism of fungal resistance to their own metabolites are described. The physiological role of the naphthoquinones in producers is discussed.

Studies of the teratogenicity of xanthomegnin and viridicatumtoxin in ICR mice

The myotoxins xanthomegnin and viridicatumtoxin were not teratogenic when administered orally to pregnant ICR mice during the 8-12th and 8-13th days of gestation, respectively. Viridicatumtoxin produced high mortality in mice given 200, 250 or 350 mg/kg of body weight.

Penicillium viridicatum, Penicillium verrucosum, and production of ochratoxin A

The taxonomy of the important mycotoxigenic species Penicillium viridicatum and P. verrucosum was reviewed to clarify disagreements relating to the three P. viridicatum groups erected by Ciegler and coworkers (A. Ciegler, D. I. Fennell, G. A. Sansing, R. W. Detroy, and G. A. Bennett, Appl. Microbiol. 26:271-278, 1973) and the mycotoxins produced by them. Cultures derived from the types of these two species and authentic cultures from each group and from many other sources were examined culturally, microscopically, and for mycotoxin production. It was concluded that P. viridicatum group II has affinities with P. verrucosum and not with P. viridicatum, as indicated by J. I. Pitt in the 1979 monograph (The Genus Penicillium and Its Teleomorphic States Eupenicillium and Talaromyces). As a result of this study it can now be unequivocally stated that the mycotoxins ochratoxin A and citrinin are not produced by P. viridicatum. Of species in subgenus Penicillium, only P. verrucosum is known to produce ochratoxin A.

Toxic fungal metabolites in food

About 100 fungal metabolites may cause cancer, embryological defects, or other histopathological effects in mammals. They are produced by a wide variety of fungi. Few of these metabolites have significant acute toxicity. With the exception of aflatoxin B1 and sterigmatocystin, there is no conclusive evidence that any of them is carcinogenic. However, several of the compounds are mutagenic. Cytochalasin D and T-2 toxin are probably teratogenic. A wide variety of other histopathological effects have been shown. Liver damage has been most frequently reported. In almost all cases the molecular bases of these effects have not been extensively investigated. Although much is known about the routes by which some of the compounds are synthesized in vivo, nothing is known about control at the molecular level of these biosynthetic routes. Little is known about the biological degradation of these compounds or about the levels and incidences of them in food and animal feed. Future work in all these areas will depend on the further development of sensitive assay methods that are applicable to their measurement in food, in animal feed, and in animal tissues and body fluids and on the application of these methods to define exposure to these compounds in the diet.

Natural occurrence of the mycotoxin viomellein in barley and the associated quinone-producing penicillia

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.

Genotoxicity of quinone pigments from pathogenic fungi

The genotoxicity and mutagenicity of several kinds of quinone pigments from pathogenic fungi were examined by means of the hepatocyte primary culture (HPC)/DNA repair test and of Ames test with TA98 and TA100. Clear genotoxicity of the two quinone chemicals, xanthomegnin and luteosporin were observed in the HPC/DNA repair test, though definite mutagenicity was not detected in the Salmonella microsome test. These two pigments are thus suspected to be genotoxic carcinogens.

Isolation of xanthomegnin from Penicillium viridicatum by preparative high-pressure liquid chromatography

A method was developed for the production and purification of xanthomegnin from Penicillium viridicatum (NRRL 6430) cultured on rice at 15 degrees C for 29 days. Liquid-liquid extraction followed by high-pressure liquid chromatography afforded 440 mg of crystalline xanthomegnin per kg of rice.

Production of Naphthoquinone Mycotoxins and Taxonomy of Penicillium viridicatum

Groups I and II of Penicillium viridicatum were further differentiated on the basis of synthesis of two mycotoxins, xanthomegnin and viomellein. Strains previously classified as group II produced these pigments, whereas those in group I did not. These napthoquinone pigments were quantitated by thin-layer chromatography and high-pressure liquid chromatography. A new mobile phase of toluene and acetic acid effected a baseline separation of the two components. It is proposed that such biochemical distinctions be incorporated into an artificial taxonomic scheme of use to nontaxonomists.

Mycotoxicosis produced in swine by cultural products of an isolate of Aspergillus ochraceus. I. Clinical observations and pathology

Pigs fed a ration, 25% of which was rice culture, of Aspergillus ochraceus lost weight or failed to gain and became depressed. Some pigs died and most developed subcutaneous edema, hydrothorax, hydroperitoneum, pulmonary atelectasis, edema of the mesentery and perirenal edema. Microscopic lesions in addition to edema were primarily renal and consisted of tubular degeneration and necrosis, hyaline tubular casts, interstitial fibrosis and tubular cell regeneration. The first change found after 3 days was cytoplasmic vacuolation of the convoluted and straight segments of the proximal tubules. Necrotic proximal tubules were found after 4 days and after 9 days degeneration and necrosis involved predominantly proximal tubular segments. Pigs fed a ration, 12.5% of which was rice culture, for 8 weeks did not develop perirenal edema but had firm kidneys. Extensive interstitial fibrosis of the cortical labyrinth was the principal change. Within the fibrous connective tissue, some tubules were necrotic and others were atrophied.

Carotenogenesis associated with arthrosporulation of Trichophyton mentagrophytes

Carotenoid pigments were demonstrated in arthrospores of the dermatophyte Trichophyton mentagrophytes but were absent from hyphae and microconidia of this fungus. Incubation at higher temperatures (39 degrees C) allowed arthrosporulation to occur, but essentially no carotenoid was detected in such arthrospores. The carotenoid formation in arthrosporulating T. mentagrophytes did not appear to be either induced or stimulated by light illumination. Mature arthrospores contained the carotenoids phytoene, phytofluene, zeta-carotene, neurosporene, lycopene, and gamma-carotene and a few minor unidentified carotenoids. These carotenoids were localized within intracellular granules consisting of osmiophilic matrices and complex membranous elements. This is the first demonstration of carotenoid pigments in dermatophytic fungi.

Production of xanthomegnin and viomellein by species of Aspergillus correlated with mycotoxicosis produced in mice

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.

Production of xanthomegnin and viomellein by isolates of Aspergillus ochraceus, Penicillium cyclopium, and Penicillium viridicatum

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.

Mycotoxicosis produced in rats by cultural products of an isolate of Aspergillus ochraceus

The toxicity of an isolate of Aspergillus ochraceus was examined in weanling male Sprague-Dawley rats fed diets containing a rice culture or fungal mat of the organism for 5 wk. The ground rice culture was mixed with a commercial purified diet at concentrations of 5, 7·5 and 10% and the fungal mat at concentrations of 1, 2 and 3%. In groups fed the rice-culture diets, weight gains were reduced and all the rats in the group fed the 10% diet died. Rats fed fungal-mat diets showed a marked reduction in weight gain, and the death rate was high (about 83%) in groups fed the 2 or 3% diet. Gross lesions found in groups fed either type of diet included focal necrosis in the liver, greenish discoloration of the kidneys, gastric ulceration, ulceration of the scrotal epidermis and corneal opacity. Histological changes in the liver included necrosis of the epithelium of biliary ducts, periductal oedema, pericholangitis, periductal fibrosis and disseminated focal hepatocellular necrosis. Necrosis of epithelium occurred also in the extraheptic ducts and was accompanied by an interstitial pancreatitis in certain rats. Foci of leucocytes and macrophages were found in the dermis of the scrotum and in the epididymal adipose connective tissue. Ulceration of the epidermis occurred late in the sequence of scrotal changes. Ocular lesions comprised corneal oedema, interstitital keratitis, iridocyclitis and hypopyon. Renal lesions consisted of tubular necrosis and hyaline and biliary casts within convoluted tubules.

Metabolic products of microorganisms 167. Cyclopaldic acid from Aspergillus duricaulis. 1. Production, isolation and bioloical properties

In the course of a screening for new metabolites from fungi we isolated a substance with antimicrobial activity from cultures of Aspergillus duricaulis (CBS 481.65) (Tü 679). It was antagonized by putrescine, spermidine, spermine, arginine, citrulline, lysine, ornithine, in higher concentration by aspraagine and glutamine too. The effect of ethylenediaminetetraacetate on the susceptibility of Streptomyces viridochromogenes (Tü 57) and Bacillus subtilis ATCC 6051 to this antibiotic has been studied. The substance was characterized and identified as cyclopaldic acid.