Suppression of aflatoxin production in Aspergillus species by selected peanut (Arachis hypogaea) stilbenoids

Authors: Sobolev, Victor; Arias De Ares, Renee; Goodman, Kerestin; Walk, Travis; Orner, Valerie; Faustinelli, Paola; Massa, Alicia

Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/5/2017
Publication Date: 12/5/2017
Citation: Sobolev, V., Arias De Ares, R.S., Goodman, K.E., Walk, T., Orner, V.A., Faustinelli, P.C., Massa, A.N. 2017. Suppression of aflatoxin production in Aspergillus species by selected peanut (Arachis hypogaea) stilbenoids. Journal of Agricultural and Food Chemistry. 66:118-126.

Interpretive Summary: Aflatoxins are toxic carcinogenic compounds that are produced by a common soil fungus Aspergillus flavus (A. flavus). It was estimated that over a half of the world population is chronically exposed to aflatoxins. Preharvest aflatoxin contamination of peanuts caused by A. flavus is a serious health and economic problem. Peanut plants are most susceptible to invasion by A. flavus under conditions leading to drought stress. However, in irrigated fields peanut plants demonstrate an appreciable resistance to fungal invasion. This resistance has been attributed to phytoalexins. Peanut phytoalexins are low-molecular-weight antimicrobial compounds that are synthesized and accumulate in the plant after exposure to a fungal attack. Present research demonstrated that under laboratory conditions peanut phytoalexins significantly reduced, or completely suppressed aflatoxin production in A. flavus. Changes in fungal spore germination and growth rate were observed in one of the strains of A. flavus exposed to selected peanut phytoalexins. Elucidation of the mechanism of aflatoxin suppression by peanut phytoalexins could provide strategies for preventing plant invasion by the fungi that produce aflatoxins.

Technical Abstract: Aspergillus (A.) flavus is a soil fungus that commonly invades peanut seeds and often produces the carcinogenic aflatoxins. Under favorable conditions, the fungus-challenged peanut plant produces and accumulates resveratrol and its prenylated derivatives in response to such 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 effect on the viability and metabolite production by several important toxigenic Aspergillus species. Significant reduction, or complete suppression of aflatoxin production was revealed in feeding experiments in A. flavus, A. parasiticus, and A. nomius. Changes in morphology, spore germination and growth rate were observed on A. flavus exposed to 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.