The antibiotic properties of macrocyclic trichothecene mycotoxins]

Some trichotecenic mycotoxins (verrucarine A, roridines A and H, T-2-toxin) have been studied for their antibiotic effect on a wide spectrum of the yeast cultures (761 strains). The studied substances differ both in their activity and the action character. The yeast strains promising for development of microbiological methods of indication and detoxification of mycotoxins have been revealed.     

Methods of detecting and determining nitrogen-containing mycotoxins]

The influence of various nitrogen functional groups used for extraction cleanup and determination of N-containing mycotoxins (NM) in feeds and foodstuffs have been considered. TLC and LC are the most common techniques for detection and determination of nitrogen-containing mycotoxins. Gas chromatography has been used for determination (with or without derivatization) of several nitrogen-containing mycotoxins and/or their degradation products. Immunochemical techniques, in particular ELISA are available for only a very limited number of NM (e.g. ochratoxin A). Numerous methods for determination of ochratoxin A in feeds, grains, animal products and other foodstuffs have been developed. Methods for which recoveries have been carried out on spiked samples are also available for several other NM.     

Emerging mycotoxins: introduction

Mycotoxins are a diverse group of secondary metabolites produced by moulds. They have a wide range of toxicological effects both in humans and animals. Nowadays about 200 of these metabolites have been described, but only a few of them may be considered as important from the agricultural point of view. In this publication, some aspects such as mycotoxin producing species, analytical methods, natural occurrence, preventive and detoxification techniques and regulations of these kind of mycotoxins will be developed by different authors involved in these research issues.     

短瓣花中的含氮化合物

从云南民间草药短瓣花（Brachystemma calycinum D.Don)根的乙醇提取物中首次分到6个化合物,包括5个含氮化合物及1个可能的人工产物。它们的结构经光谱及化学方法鉴定为短瓣花苷A（brachystemoside A,1),L- 焦谷氨酸甲酯（methyl L-pyroglutamate,2),腺嘌呤核苷（adenosine,3),2-吡咯甲酸（2－minaline,4),吡咯－2－羧酸－3'－糖酯（3'-furfuryl-pyrrole-2-carboxylate,5)及α－D－乙基葡萄糖苷（ethyl α－D－glucopyranoside,6)。其中化合物1为新化合物。     

Biological detoxification of mycotoxins: a review

Mycotoxins are secondary fungal metabolites and are reported to be carcinogenic, genotoxic, teratogenic, dermato-, nephro- and hepatotoxic. Several studies have shown that economic losses due to mycotoxins occur at all levels of food and feed production, including crop and animal production, processing and distribution. Therefore, there is a great demand for a novel approach to prevent both the formation of mycotoxins in food and feed and the impact of existing mycotoxin contamination. Recently, investigators have reported that many microorganisms including bacteria, yeast, moulds, actinomycetes and algae are able to remove or degrade mycotoxins in food and feed. We have reviewed various strategies for the detoxification of mycotoxins using microorganisms such as bacteria, yeast and fungi.     

Mollicellins: mutagenic and antibacterial mycotoxins.

Eight mollicellins (depsidones) were assayed for mutagenicity and antibacterial activity in Salmonella/microsome tests involving histidine reversion and forward mutation to 8-azaguanine resistance. Two of them, mollicellins C and E, which contain a 3-methylbutenoic acid moiety, were mutagenic and bactericidal for Salmonella typhimurium in the absence of microsomes. Mollicellins D and F, each containing a chlorine atom, were bactericidal but not mutagenic. The mutagenic activity was completely abolished and the antibiotic activity was greatly reduced by coincubation with rat liver microsomes.     

Mollicellins: mutagenic and antibacterial mycotoxins.

Eight mollicellins (depsidones) were assayed for mutagenicity and antibacterial activity in Salmonella/microsome tests involving histidine reversion and forward mutation to 8-azaguanine resistance. Two of them, mollicellins C and E, which contain a 3-methylbutenoic acid moiety, were mutagenic and bactericidal for Salmonella typhimurium in the absence of microsomes. Mollicellins D and F, each containing a chlorine atom, were bactericidal but not mutagenic. The mutagenic activity was completely abolished and the antibiotic activity was greatly reduced by coincubation with rat liver microsomes.     

Fungi that produce mycotoxins: Conditions and occurrence

The occurrence of mycotoxins, in agricultural commodities is a worldwide problem with almost all commodities being potentially susceptible to contamination under the proper conditions. The genera of fungi most implicated are Aspergillus, Penicillium and Fusarium, although the potential for toxin production varies considerably within any given species.Conditions that affect toxin production include fungal strain variation, genetic susceptibility of the host plant or commodity, moisture content, commodity composition, temperature, aeration, microbial population and stress factors. There is undoubtedly interaction between these factors so that laboratory studies involving limited variables can only, at best, approximate field conditions.Natural contamination with mycotoxins has been reported for most of the major agricultural commodities in the world including corn, wheat, rice, millet, barley, oats, sorghum, peanuts, beans, copra, some fruits and nuts and various forages; strangely, soybeans do not appear to be involved to any major extent. The major mycotoxins on commodities reported to date include aflatoxin, the trichothecenes, ochratoxin, citrinin, zearalenone, sporidesmins and some tremorgens. However, laboratory studies have shown that the fungi are capable of producing hundreds of toxic chemicals, most of which are not included in routine analyses. In addition, since toxin effects are often insidious and may go undetected, the true dimensions of the mycotoxin problem are unknown.     

Nitrogen-containing compounds from Solanum lyratum Thunb

The medicinal plant Solanum lyratum Thunb（Solanaceae）is distributed widely in China. The present phytochemical investigation on S. lyratum led to the isolation of ten known Nitrogen-containing compounds. Compounds 1, 2, 3, 6, 9 were isolated for the first time from this plant and compounds 8,10 were obtained for the first time from Solanum. Compound 10 was isolated from Solanaceae family and obtained outside from Loganiaceae family for the first time. This has important chemotaxonomic significance on solanaceae.     

Pine nuts: the mycobiota and potential mycotoxins

The mycobiota of pine nuts was investigated. In total, 1832 fungi belonging to 31 species and 15 genera (Ascomycota, 2; Zygomycota, 3; mitosporic fungi, 10) could be isolated. Cladosporium spp. dominated the mycobiota with 685 isolations followed by Phoma macrostoma with 351 isolations. Overall, 16 potentially mycotoxigenic species were present on pine nuts.     

Fiber-optic immunosensor for mycotoxins

Evanescent wave-based fiber-optic immunosensors were studied for the detection of fumonisins and aflatoxins in maize. Two formats, competitive and non-competitive, were used. A competitive format was used to measure fumonisin B1 (FB1) in both spiked and naturally contaminated maize samples. Fumonisin monoclonal antibodies were covalently coupled to an optical fiber and the competition between FB1 and FB1 labeled with fluorescein (FB1-FITC) for the limited number of binding sites on the fiber was assessed. The signal generated in the assay was inversely proportional to the FB1 concentration. For samples, the concentration causing an inhibition of binding by 50% (IC50) was dependent upon the clean-up procedure used. Simple dilution of methanolic maize extracts yielded an assay with an IC50 equivalent to 25 microg FB1 g(-1) maize with a limit of detection of 3.2 microg g(-1) maize. Affinity column clean-up yielded an assay with an IC50 equivalent to 5 microg FB1 g(-1) maize (limit of detection 0.4 microg FB1 g(-1)). An HPLC method and the immunosensor method agreed well for naturally contaminated maize samples except when large amounts of other fumonisins that cross-react with the immunosensor were present. The second sensor format, for the mycotoxin aflatoxin B1 (AFB1), was a non-competitive assay using the native fluorescence of this mycotoxin. Because the fluorescence of AFB1 itself was detected, the response of the sensor was directly proportional to the toxin concentration. The sensor, while capable of detecting as little as 2 ng ml(-1) of AFB1 in solution was technically not an immunosensor, since the attachment of aflatoxin specific antibodies was not required. Sensors of the formats described have the potential to rapidly screen individual maize samples but require coupling with a clean-up technique to be truly effective.     

Nitrogen-containing phorbol derivatives of Sapium indicum

From the ether-soluble fraction of an extract of Sapium indicum two new nitrogen-containing esters of deoxyphorbol, sapintoxins B and C, were isolated. Both were characterized by the bright blue fluorescence which they exhibited in UV light. Sapintoxin B was identified as 12-(N-methylaminobenzoyl)-4-deoxy-5-hydroxyphorbol-13-acetate and sapintoxin C as 12-(N-methylaminobenzoyl)-4,20-dideoxy-5-hydroxyphorbol-13-acetate.     

Biosynthesis of sphinganine-analog mycotoxins

Sphinganine-analog mycotoxins (SAMT) are polyketide-derived natural products produced by a number of plant pathogenic fungi and are among the most economically important mycotoxins. The toxins are structurally similar to sphinganine, a key intermediate in the biosynthesis of ceramides and sphingolipids, and competitive inhibitors for ceramide synthase. The inhibition of ceramide and sphingolipid biosynthesis is associated with several fatal diseases in domestic animals and esophageal cancer and neural tube defects in humans. SAMT contains a highly reduced, acyclic polyketide carbon backbone, which is assembled by a single module polyketide synthase. The biosynthesis of SAMT involves a unique polyketide chain-releasing mechanism, in which a pyridoxal 5'-phosphate-dependent enzyme catalyzes the termination, offloading and elongation of the polyketide chain. This leads to the introduction of a new carbon-carbon bond and an amino group to the polyketide chain. The mechanism is fundamentally different from the thioesterase/cyclase-catalyzed polyketide chain releasing found in bacterial and other fungal polyketide biosynthesis. Genetic data suggest that the ketosynthase domain of the polyketide synthase and the chain-releasing enzyme are important for controlling the final product structure. In addition, several post-polyketide modifications have to take place before SAMT become mature toxins.