This is the first study focused on using AgNPs in control of OTA production.
Silver nanoparticles (AgNPs) have potential antimicrobial activity against bacteria and fungi. The synthesis of AgNPs have been reported using several chemical and physical methods which are not friendly environment. Therefore, our technique has focused on the synthesis of AgNPs by natural compounds. The aim of this study has been to synthesis AgNPs by safe nontoxic method using Egyptian honey (EH) as reducing and capping agents and to investigate its ability to reduce the mycelial growth and the production of aflatoxins (AFs) and ochratoxin A (OTA) by Aspergillus flavus and Aspergillus ochraceus, respectively. AgNPs have been characterized by UV-Visible Spectrophotometer, Dynamic Light Scattering (DLS), Fourier Transform Infrared Spectroscopy (FTIR), and Transmission Electron Microscope (TEM).The obtained results indicated that the synthesis of honey AgNPs depends on the concentration of bulk metal (AgNO3) used in the synthesis process. The TEM image has revealed the formation of spherical well dispersed AgNPs, while the main size of AgNPs detected by DSL is 9.9 nm. Our results have indicated that 3 mg -100 ml media of honey derived AgNPs have reduced the aflatoxin (AF) G1, G2, B1 andB2 production by A. parasiticus to 77.55, , 62.91, 58.76 and 66.56%, respectively and ochratoxin A (OTA) by A. ochraceus to 79.85 % with significantly inhibitory effect on mycelial growth. The percentage of reduction depends on the AgNPs concentration.
AIM:In this study, we evaluated the effect of silver nanoparticles (AgNPs) on the production of aflatoxin B1 (AFB1) through assessment the transcription activity of aflatoxin biosynthesis pathway genes in Aspergillus flavus ATCC28542.MATERIAL AND METHODS:The mRNAs were quantitative by Real Time-polymerase chain reaction (qRT-PCR) of A. flavus grown in yeast extract sucrose (YES) medium containing AgNPs. Specific primers that are involved in the AFB1 biosynthesis which highly specific to A. flavus, O-methyltransferase gene (omt-A), were designed and used to detect the fungus activity by quantitative PCR assay. The AFB1 production (from A. flavus growth) which effected by AgNPs were measured in YES medium by high-pressure liquid chromatography (HPLC).RESULTS:The AFB1 produced by A. flavus have the highest reduction with 1.5 mg -100 ml of AgNPs were added in media those records 88.2%, 67.7% and 83.5% reduction by using AgNP HA1N, AgNP HA2N and AgNP EH, respectively. While on mycelial growth give significantly inhibitory effect. These results have been confirmed by qRT-PCR which showed that culture of A. flavus with the presence of AgNPs reduced the expression levels of omt-A geneCONCLUSION:Based on the results of the present study, AgNPs inhibit growth and AFB1 produced by Aspergillus flavus ATCC28542. This was confirmed through RT-PCR approach showing the effect of AgNPs on omt-A gene involved in aflatoxin biosynthesis.
Objectives: The present study was prepared to investigate the impact of insect density, adult emergence of Tribolium castaneum on the secretion of Benzoquinones (BQs) consist of methyl-1,4-benzoquinone(MBQ) and Ethyl-1,4-Benzoquinone (EBQ), and accumulation of Aflatoxins (AFs) in wheat flour stored at different periods. Methods: Forty grams of wheat flour were put into small glass jars (8 cm diameter and 12 cm length). Then T. castaneum was put in each jars at rates of 10, 20 and 30 unsexed pairs of insect adult. The jars were covered with muslin cloth and the rubber band was fixed to prevent insects to escape. A glass jar without any insects served as the control. The jars lifted on bench in the laboratory for two, three and four months of storage under laboratory temperature conditions (with average 28 ± 20C and 65±5 R.H). The previous design was replicated three times. At the end of each storage period, the jars containing the flour were sieved thoroughly by 40 wire mesh size to separate the insects. The insects have been counted on the other hand wheat flour was prepared to determine MBQ, EBQ and AFs by HPLC methods. Results: The results indicated the levels of EBQ higher than MBQ in all infested samples at all insect densities (No. of insect pairs). The concentrations of MBQ in wheat flour released by ten adult pairs (10P) with the three storage periods two, three and four months were 10.42 ± 0.56, 22.38 ± 3.67, 27.06 ± 6.71µg/g, respectively. These results increased with insect densities to (30p) were 39.67 ± 0.10, 63.58 ± 2.35 and 106.24 ± 7.4 µg/g after storage periods two, three and four months, respectively. In addition to the concentrations of EBQ with (10P) were 67.45 ± 3.64, 98.0 ± 6.1 204.66 ± 5.8 µg/g with storage periods two, three and four months, respectively. In case (30P) the levels of EBQ were 376.7 ± 0.87, 570.1 ± 2.11 and 1558.66 ± 10.88 (µg/g). The highest concentration of the BQs 1664.90 ± 11.43 (µg/g) released by T. castaneum achieved with the highest adult emergence (1021 insect adult) and the highest insect density (30p) at four months storage period. In general, AFs levels enhanced with a period of storage and insect densities. Conclusion: Levels of the BQs (MBQ and EBQ) increased with an increase of storage periods and insect densities. Therefore, the presence of this insect should be prevented in stored wheat flour reducing AFs contamination is possible by storage for short time and prohibit insects which causes an increase temperature of the flour and moisture, all of which promote production of AFs.
Plants are one of a prefect source of natural effective compounds that have antimicrobial, and other activities. This study investigated the activity of the aqueous extract for three wild edible plants ( Sonchus oleraceus , Cichorium pumilum, and Portulaca oleracea ) at three concentrations (1.5, 2.5 and 5 mg/ml) as antifungal and antitoxigenic. Many functional groups such as alcohols, phenols, alkanes and alkenes, etc were appeared in aqueous extracts by Fourier Transform Infrared Spectroscopy (FTIR) analysis. Where an extract of Portulaca oleracea gave a greater total phenolic and flavonoids were 210.4 ± 1.15 and 36.7 ± 0.79 mg/mL, respectively, followed by Sonchus oleraceus (192.3 ± 2.11 mg/mL) and Cichorium pumilum (186.4 ± 2.18 mg/mL). The results indicated that increasing the concentration of the extract, the area of inhibition zone increased with all treatments, where the highest inhibition zone was observed using 5 mg/ml for Portulaca oleracea extract was 17.1 ± 1.7, 26.5 ± 1.5 and 22.8.±2.3 mm against Aspergillus flavus, Aspergillus ochraceus and Aspergillus parasiticus , respectively, while the lowest antifungal activity was marked with Cichorium pumilum extract with all tested fungi. The results have also indicated that the aqueous extract has inhibited formed of aflatoxin B 1 (AFB 1 ) and ochratoxin A (OTA), where the percentages of inhibition AFB 1 were 78.03, 68.8 and 81.7% after treated yeast extract sucrose (YES) media by 5 mg crude extract for extract Sonchus oleraceus, Cichorium pumilum and Portulaca oleracea , respectively. In contrast, the inhibitory effect against OTA at the same concentration was 77.5, 72.3, and 85.2% in the same order for plants. Finally, these plants provide an aqueous extract that contains many effective compounds that enable to play the role of antifungal and antitoxigenic .
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