Suppression of Aflatoxin Production in Aspergillus Species by Selected Peanut (Arachis hypogaea) Stilbenoids

Abstract

Aspergillus flavus is a soil fungus that commonly invades peanut seeds and often produces carcinogenic aflatoxins. Under favorable conditions, the fungus-challenged peanut plant produces and accumulates resveratrol and its prenylated derivatives in response to such an invasion. These prenylated stilbenoids are considered peanut antifungal phytoalexins. However, the mechanism of peanut−fungus interaction has not been sufficiently studied. We used pure peanut stilbenoids arachidin-1, arachidin-3, and chiricanine A to study their effects on the viability of and metabolite production by several important toxigenic Aspergillus species. Significant reduction or virtually complete suppression of aflatoxin production was revealed in feeding experiments in A. flavus, Aspergillus parasiticus, and Aspergillus nomius. Changes in morphology, spore germination, and growth rate were observed in A. flavus exposed to the selected peanut stilbenoids. Elucidation of the mechanism of aflatoxin suppression by peanut stilbenoids could provide strategies for preventing plant invasion by the fungi that produce aflatoxins.

Inhibition of Aflatoxin Formation in Aspergillus Species by Peanut (Arachis hypogaea) Seed Stilbenoids in the Course of Peanut–Fungus Interaction

“…Such a correlation may be attributed to a probable conversion of stilbenoid 2 into 4 through 1 within the time frame of the experiments, as earlier suggested. 32 In agreement with our previous research, 26 production of aflatoxin B 1 in some experiments did not necessarily positively correlate with the degree of fungal colonization of wounded seeds as apparent from Table A of the Supporting Information. The present research demonstrated that in the course of peanut−fungus interaction, in the majority of experiments, aflatoxin production was suppressed in all fungi tested when lower concentrations of spores were applied to wounded seeds; with all fungi tested, higher concentrations of aflatoxin B 1 (5) were produced with a higher concentration of spores and shorter incubation times before spore application; production patterns of aflatoxin B 2 and the primary aflatoxin precursor, norsolorinic acid (6), were very similar to that of aflatoxin B 1 ; of all experimental seeds that showed fungal growth, 57.7% were aflatoxin-free after 72 h of incubation; overall production of stilbenoids was not significantly different between experiments with different fungi tested; concentrations of stilbenoids in wounded peanuts increased with higher concentrations of spores contacting them; compared to the control, the composition of stilbenoids changed significantly upon interaction with fungal structures; phytoalexin profiles and production changed with incubation time before fungal application and the number of spores applied; formation of SB-1 (4) was observed only in the presence of fungal spores or actively growing fungi; arachidin-1 (1) was the predominant phytoalexin in all the experiments with the exception of the experiment with the most aggressive fungus, A. flavus NRRL 29487, 500 spores used, and zero and 24 h of incubation before spore application.…”

Peanut (Arachis hypogaea L.): A Prospective Legume Crop to Offer Multiple Health Benefits Under Changing Climate

“…Recently, peanut plants with higher resveratrol content exhibited suppression in AF production by Aspergillus spp. (Sobolev et al., ). In an overall assessment, proper management of agricultural practices and the harvested crop are important aspects to minimize AF contamination (suggested readings Kumar et al., ; Matumba et al., ; Sobolev et al., ; Udomkun et al., ).…”

Presence of resveratrol in wild Arachis species adds new value to this overlooked genetic resource

“…The characterization of the genus has included studies on genetic diversity and phylogenetic analysis, and evaluation of different species for their resistance to several biotic and abiotic stresses 10 , 11 . Species from genus Arachis are among the few plant species that naturally synthesize resveratrol, a phytoalexin that protects plants against biotic and abiotic stresses 12 – 14 . Resveratrol is also well known for its potent antioxidant properties, and as a therapeutic agent in the prevention or treatment of many human diseases, including neoplastic, metabolic, cardiovascular, pulmonary and neurological disorders 15 – 17 .…”