Cyclodextrins as modifiers of the luminescence characteristics of aflatoxins

Vázquez, Maribel; Cepeda, Alberto; Prognon, Patrice; Mahuzier, G.; Blais, J.

doi:10.1016/0003-2670(91)80066-3

Cited by 44 publications

(31 citation statements)

References 26 publications

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“…They are available commercially, and their physical and chemical properties have been described in the literature (14). These oligomers are able to include a large number of organic and inorganic species in their cavities, and in this work, excitation of the natural fluorescence of aflatoxins has been accomplished using a derivative of these molecules (2,8,16,17).Experimental results obtained in previous work (2, 16, 17) revealed that ␤-cyd and its methylated derivatives have excellent cavities for exciting the fluorescence responses of aflatoxins B 1 and G 1 through the formation of inclusion complexes. In this work, we have exploited this property for the direct visual measurement of aflatoxin production by A. flavus and A. parasiticus strains.…”

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New Additive for Culture Media for Rapid Identification of Aflatoxin-Producing Aspergillus Strains

Fente

Ordaz

Vázquez

et al. 2001

Appl Environ Microbiol

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A new reliable, fast, and simple method for the detection of aflatoxigenic Aspergillus strains, consisting of the addition of a cyclodextrin (a methylated ␤-cyclodextrin derivative) to common media used for testing mycotoxin production ability, was developed. We propose the use of this compound as an additive for fungal culture media to enhance the natural fluorescence of aflatoxins. The production of aflatoxins coincided with the presence of a bright blue or blue-green fluorescent area surrounding colonies when observed under longwavelength (365-nm) UV light after 3 days of incubation at 28°C. The presence of aflatoxins was confirmed by extracting the medium with chloroform and examining the extracts by high-pressure liquid chromatography with fluorescence detection.Aflatoxins are mycotoxins with highly toxic and carcinogenic properties produced by some strains of Aspergillus flavus, Aspergillus parasiticus, and Aspergillus nomius. These fungi are frequently found in foodstuffs and animal feeds. However, not all strains are able to produce aflatoxins, and this has encouraged the use of screening for their aflatoxin production abilities. The methodology commonly used for this survey involves the culture of strains in a suitable liquid or solid medium and their later extraction and analysis for the presence of aflatoxins by chromatographic techniques. Yeast extract-sucrose (YES) medium (3) and natural media with wheat, rice, or peanut (9) have been used for this purpose. Testing large numbers of isolates on a variety of substrates with this procedure is tedious and time-consuming. For this reason, several screening methods for direct visual determination of aflatoxin production have been developed. These methods use more or less complicated culture media containing additives to enhance the production of aflatoxins in order to achieve direct visual determination of a bright blue or blue-green fluorescent area surrounding colonies under UV radiation. Thus, a complex agar medium containing sucrose, various salts, and an aqueous extract of aflatoxin-free peanuts (5); a modified Czapek agar medium containing corn steep liquor, named aflatoxin-producing ability (APA) medium (9); media containing coconut, named coconut agar medium (4, 13), coconut extract agar (11,12), and coconut cream agar (6); the synthetic liquid medium of Adye and Mateles (1); and a silica gel medium (15) are currently in use.The natural fluorescence of aflatoxins arises from their oxygenated pentaheterocyclic structure. The cyclodextrins (cyd) are molecules formed by the action of the enzyme cyd-transglycolase on dextrans and have different sizes [they contain from six to eight units of glucose in an ␣(1-4) configuration, according to which they are called ␣-, ␤-, or ␥-cyd]. They are available commercially, and their physical and chemical properties have been described in the literature (14). These oligomers are able to include a large number of organic and inorganic species in their cavities, and in this work, excitation of the natural fluorescen...

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New Additive for Culture Media for Rapid Identification of Aflatoxin-Producing Aspergillus Strains

Fente

Ordaz

Vázquez

et al. 2001

Appl Environ Microbiol

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“…The results of the three methods are comparable: the Iluorescence intensities for B, and G, are improved to the level of the B, and G, species in aqueous solutions. Since the fluorescence quantum yields of the latter species are already high [69], further significant improvements of the derivatization methods are not to be expected.…”

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“…Later spectroscopic studies [69] showed that cY-cyclodextrins have the same effect, while y-cyclodextrins are not effective.…”

Section: Other Post-column Derivatization Methodsmentioning

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Derivatization reactions for the determination of aflatoxins by liquid chromatography with fluorescence detection

Kok

1994

Journal of Chromatography B: Biomedical Sciences and Applicatio

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Various derivatization methods for the fluorometric detection of aflatoxins after separation by HPLC are reviewed. In normal-phase chromatography the sensitivity for aflatoxins B, and B, was improved by using special mobile phases or a flow cell packed with silica-gel particles. In the nowadays more popular reversed-phase methods, the fluorescence intensity of B, and G, can be increased by precolumn derivatization with trifluoroacetic acid or by postcolumn derivatization with iodine or bromine. Optimum conditions for the reactions are discussed. In terms of sensitivity, the three derivatization schemes give similar results. The methods are compared with respect to experimental convenience, selectivity, reproducibility and suitability for automation.

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“…Like many others heterocyclic fluoresce compounds, AFs also are distinguished by native fluorophore characteristics. AFB1 and AFB2 fluoresce blue color while AFG1 and AFG2 are endowed with yellow-green fluoresce under ultraviolet light (Hussein and Brasel, 2001;Vazquez et al, 1991). The abbreviations B and G show Blue and Green color, while 1 and 2 represents the relative migration distance, 1(higher) and 2 (lower) of the compounds as seen on a thin-layer chromatographic plate under ultraviolet light (Klich, 2007).…”

Section: Aspergillus Flavus and Aspergillus Parasiticusmentioning

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Current Maize Production, Postharvest Losses and the Risk of Mycotoxins Contamination in Tanzania

Suleiman¹,

Rosentrater²

2015

2015 ASABE International Meeting

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Agriculture is the backbone of Tanzanian economy. It accounts for about one-third of the gross domestic product (GDP), provides 85 percent of all exports and saves as a livelihood to over 80 percent of the total population. Maize is the primary staple crop; it's grown in nearly all agro-ecological zones in the country. Tanzania is a major maize producer in Sub-Saharan Africa. In the last four decades, Tanzania has ranked among the top 25 maize producing countries in the world. In the 2013/14 growing seasons Tanzania produced over half billion metric tons of maize of these maize smallholder farmers produced around 85%. Despite the steady production of maize over the past three decades, post-harvest losses of maize remained significant, up to 30-40 % in some rural areas. Post-harvest handling, poor infrastructure, weather variability, biotic factors such as insects and pests, bacteria, pathogens, viruses, and fungi, often aggravate such losses. Mycotoxin producing fungi pose a major risk. Mycotoxins are toxic secondary metabolites of fungi that frequently contaminate the maize in the field and/or during storage. Mycotoxin contamination of maize poses a health risk to humans and animals if not properly managed. The most important mycotoxins in Tanzania are the aflatoxins, fumonisins and Ochratoxin. The objective of this paper was to review current literature on the production trends, consumption, post-harvest losses, and mycotoxins contamination of maize and to provide strategies to control and prevent postharvest losses and mycotoxins contamination in Tanzania. Agriculture is the backbone of Tanzanian economy. It accounts for about one-third of the gross domestic product (GDP), provides 85 percent of all exports and saves as a livelihood to over 80 percent of the total population. Maize is the primary staple crop; it's grown in nearly all agro-ecological zones in the country. Tanzania is a major maize producer in Sub-Saharan Africa. In the last four decades, Tanzania has ranked among the top 25 maize producing countries in the world. In the 2013/14 growing seasons Tanzania produced over half billion metric tons of maize of these maize smallholder farmers produced around 85%. Despite the steady production of maize over the past three decades, post-harvest losses of maize remained significant, up to 30-40 % in some rural areas. Post-harvest handling, poor infrastructure, weather variability, biotic factors such as insects and pests, bacteria, pathogens, viruses, and fungi, often aggravate such losses. Mycotoxin producing fungi pose a major risk. Mycotoxins are toxic secondary metabolites of fungi that frequently contaminate the maize in the field and/or during storage. Mycotoxin contamination of maize poses a health risk to humans and animals if not properly managed. The most important mycotoxins in Tanzania are the aflatoxins, fumonisins and Ochratoxin. The objective of this paper was to review current literature on the production trends, consumption, post-harvest losses, and mycotoxins contamination of mai...

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Cyclodextrins as modifiers of the luminescence characteristics of aflatoxins

Cited by 44 publications

References 26 publications

New Additive for Culture Media for Rapid Identification of Aflatoxin-Producing Aspergillus Strains

New Additive for Culture Media for Rapid Identification of Aflatoxin-Producing Aspergillus Strains

Derivatization reactions for the determination of aflatoxins by liquid chromatography with fluorescence detection

Current Maize Production, Postharvest Losses and the Risk of Mycotoxins Contamination in Tanzania

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