Identification and Characterization of Peanut Seed Coat Secondary Metabolites Inhibiting <i>Aspergillus flavus</i> Growth and Reducing Aflatoxin Contamination

The peanut seed coat acts as a physical and biochemical barrier against <i>Aspergillus flavus</i> infection; however, the nature of the inhibitory chemicals in the peanut seed coat in general is not known. This study identified and characterized peanut seed coat metabolites that inhibit <i>A. flavus</i> growth and aflatoxin contamination. Selected peanut accessions grown under well-watered and water-deficit conditions were assayed for <i>A. flavus</i> resistance, and seed coats were metabolically profiled using liquid chromatography mass spectrometry. Kyoto Encyclopedia of Genes and Genome phenylpropanoid pathway reference analysis resulted in the identification of several seed coat metabolic compounds, and ten selected metabolites were tested for inhibition of <i>A. flavus</i> growth and aflatoxin contamination. Radial growth bioassay demonstrated that 2,5-dihydroxybenzaldehyde inhibited <i>A. flavus</i> growth (98.7%) and reduced the aflatoxin contamination estimate from 994 to 1 μg/kg. Scanning electron micrographs showed distorted hyphae and conidiophores in cultures of 2,5-dihydroxybenzaldehyde-treated <i>A. flavus</i>, indicating its potential use for field application as well as seed coat metabolic engineering.