Abstract
Naturally occurring coumarins possess antibacterial and antifungal properties. In this study, these natural and synthetic coumarins were used to evaluate their antifungal activities against Aspergillus flavus, which produces aflatoxins. In addition to control antifungal activities, antiaflatoxigenic properties were also determined using a high-performance liquid chromatography in conjunction with fluorescence detection. In this study, 38 compounds tested and 4-hydroxy-7-methyl-3-phenyl coumarin showed potent antifungal and antiaflatoxigenic activities against A. flavus. Inhibitory mode of antiaflatoxigenic action by 4-hydroxy-7-methyl-3-phenyl coumarin was based on the downregulation of aflD, aflK, aflQ, and aflR in aflatoxin biosynthesis. In the cases of coumarins, antifungal and aflatoxigenic activities are highly related to the lack of diene moieties in the structures. In structurally related compounds, 2,3-dihydrobenzofuran exhibited antifungal and antiaflatoxigenic activities against A. flavus. The inhibitory mode of antiaflatoxigenic action by 2,3-dihydrobenzofuran was based on the inhibition of the transcription factor (aflS) in the aflatoxin biosynthesis pathway. These potent inhibitions of 2,3-dihydrobenzofuran and 4-hydroxy-7-methyl-3-phenyl coumarin on the Aspergillus growth and production of aflatoxins contribute to the development of new controlling agents to mitigate aflatoxin contamination.
Highlights
Aflatoxins including AFB1, AFB2, AFG1, and AFG2 are mycotoxins produced by Aspergillus flavus and A. parasiticus, with potent carcinogenic activity, especially on human liver [1]
In addition to this finding, a structure–activity relationship (SAR) study of 24 coumarin derivatives showed that O-substitutions seem to be essential for antifungal activity against A. flavus and
We have found that methylenedioxy-containing natural and synthetic compounds possessed antifungal and antiaflatoxigenic properties against A. flavus [21]
Summary
Aflatoxins including AFB1, AFB2, AFG1, and AFG2 are mycotoxins produced by Aspergillus flavus and A. parasiticus, with potent carcinogenic activity, especially on human liver [1]. Molecules 2017, 22, 712 phytopathogens develop resistance to various fungicides [9,10] With this reason, alternatives for controlling Aspergillus infection and aflatoxin contamination are highly needed, and natural products could be considered as candidate compounds. Coumarins with antioxidant activities inhibit aflatoxin formation because aflatoxin formation occurs when fungal species are subject to oxidative stress [16,17,18] In addition to this finding, a structure–activity relationship (SAR) study of 24 coumarin derivatives showed that O-substitutions seem to be essential for antifungal activity against A. flavus and. 2,3-dihydrobenzofuran, indole, 1-methyl indole, 2-methyl indole, 3-methyl indole, and 2-phenyl indole to coumarins for understating relationships between the structure of tested compounds and antifungal and antiaflatoxigenic activities These antifungal and antiaflatoxigenic substances can be used for controlling A. flavus and reducing aflatoxin contamination in agricultural fields before harvest given their ability to decrease aflatoxin production
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