Gradient high-performance liquid chromatography using alkylphenone retention indices of insecticidal extracts of Penicillium strains

Tremorgenic and neurotoxic paspaline-derived indole-diterpenes: biosynthetic diversity, threats and applications

Indole-diterpenes (IDTs) such as the aflatrems, janthitrems, lolitrems, paspalitrems, penitrems, shearinines, sulpinines, and terpendoles are biogenetically related but structurally varied tremorgenic and neurotoxic mycotoxins produced by fungi. All these metabolites derive from the biosynthetic intermediate paspaline, a frequently occurring IDT on its own right. In this comprehensive review, we highlight the similarities and differences of the IDT biosynthetic pathways that lead to the generation of the main paspaline-derived IDT subgroups. We survey the taxonomic distribution and the regulation of IDT production in various fungi and compare the organization of the known IDT biosynthetic gene clusters. A detailed assessment of the highly diverse biological activities of these mycotoxins leads us to emphasize the significant losses that paspaline-derived IDTs cause in agriculture, and compels us to warn about the various hazards they represent towards human and livestock health. Conversely, we also describe the potential utility of these versatile molecules as lead compounds for pharmaceutical drug discovery, and examine the prospects for their industrial scale manufacture in genetically manipulated IDT producers or domesticated host microorganisms in synthetic biological production systems.

Production of mycotoxins by Penicillium expansum inoculated into apples

We investigated the production of mycotoxins in apple fruits inoculated with spores of 40 strains of apple blue mold, Penicillium expansum. Patulin and citrinin contents in the extracts from apples stored at 25 degrees C for 12 days after inoculation were determined by high-performance liquid chromatography (HPLC) analysis with UV and fluorescence detection. Patulin and citrinin were produced by 90% (36) and 80% (32) of the 40 strains, indicating that P. expansum is a consistent producer of these mycotoxins. The patulin content in the extracts was substantially higher than the citrinin content. Other mycotoxins whose production in pure culture has been reported were simultaneously detected with high-resolution liquid chromatography-mass spectrometry (LC-MS) analysis with the positive ion mode of electrospray ionization. Along with patulin and citrinin, expansolides A and B were identified based on the HPLC and LC-MS spectral data and detected in 88% (35) of the extracts. The results indicate that P. expansum is a consistent producer of expansolides A and B in rotten areas of apple fruits. The findings raise the possibility that products from decayed apples might contain expansolides A and B in addition to patulin and citrinin.

The isoepoxydon dehydrogenase gene of patulin biosynthesis in cultures and secondary metabolites as candidate PCR inhibitors

The European Union (EU) has introduced statutory limits for patulin in fruit products. Species definitions need to be unambiguous for this capability, especially to determine 'weak spots' in food, drink and feed production. Fungi were analysed for the isoepoxydon dehydrogenase (IDH) gene of the patulin metabolic pathway to indicate potential patulin production. In several cases inhibition of PCR product formation was indicated. Dilution as a means of overcoming PCR inhibition and to determine optimal concentrations was assessed and the ramifications for nucleic acid analysis in general are highlighted. The inhibitors may be secondary metabolites. However, inhibition was not involved obviously for Penicillium brevicompactum. The gene was detected frequently from Aspergillus section Clavati and Penicillium subgenus Penicillium species. Some strains within certain species were negative for the gene. Detection of the gene product in Byssochlamys is reported.

Determination of Penicillium mycotoxins in foods and feeds using liquid chromatography-mass spectrometry

New LC-MS (full scan) and LC-MS-MS (selected ion reaction monitoring) methods for the simultaneous determination of mycophenolic acid, griseofulvin, roquefortine C, chaetoglobosin B, verruculogen and penitrem A, and other Penicillium derived mycotoxins in food and feed samples are described. The methodologies involve sample extraction with acetonitrile-water, defatting with hexane and quantification using LC-MS with atmospheric pressure chemical ionisation or LC-MS-MS. Detector responses, for each of the methods and mycotoxins, were found to be linear over the range 10-1000 ng of mycotoxin/g of extracted food mixture material. The mean recoveries (n = 3 to 6) of the mycotoxins from spiked food mixture samples determined using MS and MS-MS detection were 87-116 and 91-112%, respectively, for mycophenolic acid, 104-109 and 91-112%, respectively, for griseofulvin, 70-85 and 75-110%, respectively, for roquefortine C, 94-109 and 81-116%, respectively, for chaetoglobosin B, 110-115 and 90-106%, respectively, for verruculogen and 78-97 and 99-108%, respectively, for penitrem A. RSDs varied from 5.6% at the 1000 ng/g level to 23.1% at the 10 ng/g level. The limits of detection for the mycotoxins using MS and MS-MS were 70 and 10 ng/g, respectively, for mycophenolic acid, 10 and 5 ng/g, respectivley, for griseofulvin, 50 and 20 ng/g, respectively, for roquefortine C, 25 and 20 ng/g, respectively, for chaetoglobosin B, 25 and 20 ng/g, respectively, for verruculogen and 10 and 5 ng/g, respectively, for penitrem A.

Mycotoxin production from fungi isolated from grapes

AIMS

In order to assess the potential for producing mycotoxins, fungi were isolated from wine producing grapes.

METHODS AND RESULTS

The isolates were identified and Penicillium expansum, the most well recognized mycotoxin producer, was analysed for mycotoxin production by TLC. Many of the strains produced patulin and/or citrinin, often depending on whether they were grown on a grape or yeast extract sucrose media.

CONCLUSION

Citrinin was produced by all strains grown in the yeast extract sucrose medium, but only one strain (from 51) was able to produce this compound in grape juice medium. Patulin was produced in the yeast extract medium by 20 strains and in grape juice medium by 33 strains.

SIGNIFICANCE AND IMPACT OF THE STUDY

The presence of mycotoxins in wine producing grapes is discussed. Grapes contamination with patulin seems not to contribute to wine contamination, and no ochratoxin producing fungi was identified.

Determination of viridicatin in Penicillium cyclopium by capillary gas chromatography

A sensitive gas chromatographic method for the determination of the quinoline alkaloid viridicatin, a fungal metabolite isolated from several Penicillium species and presumably a biogenetic precursor to naturally occurring diazepam-like 1,4-benzo-diazepines, has been developed. Prior to conversion of viridicatin into a volatile trimethylsilyl derivative, a rapid sample clean-up was accomplished by solid-phase extraction from mould mycelium on a C18 cartridge. Using synthetical 6-bromo-viridicatin as an internal standard, the amount of viridicatin produced de novo in emerged grown cultures of Penicillium cyclopium strain SM 72 was calculated in correlation to the duration of mould cultivation.

Neutral, alkaline and difference ultraviolet spectra of secondary metabolites from Penicillium and other fungi, and comparisons to published maxima from gradient high-performance liquid chromatography with diode-array detection

The ultraviolet spectra of 6 predominantly secondary metabolites from filamentous fungi which, inter alia, are useful in the identification of the compounds after chromatography, were obtained in neutral (methanol) and alkaline solvents. Difference spectra were obtained by subtracting the neutral from the alkaline spectrum for each metabolite, using the spectrophotometer software. The data and method are of use in differentiating metabolites with similar chromophores. A database of the maxima was stored on a microcomputer for flexible storage, retrieval and updating of information. These data are compared to those published previously, obtained by diode-array detection using gradient high-performance liquid chromatography, which indicated that changes in solvent concentrations of the gradient affect the spectra of some metabolites. This could cause misidentification of chemosyndromes and metabolites which have been claimed to be of use in fungal chemotaxonomy.