Identification of Phenolics for Control of Aspergillus flavus Using Saccharomyces cerevisiae in a Model Target-Gene Bioassay

Abstract

The yeast Saccharomyces cerevisiae was used in a high-throughput bioassay to identify phenolic agents for control of the aflatoxigenic fungus Aspergillus flavus. Veratraldehyde, 1, cinnamic acid, 5, and the respective benzoic acid derivatives vanillin, 2, vanillic acid, 3, and vanillylacetone, 4, and cinnamic acid derivatives o-coumaric acid, 6, m-coumaric acid, 7, and p-coumaric acid, 8, showed significant antifungal activities (from highest to lowest, 2, 5 > 1 > 6, 7 > 4 > 3, 8) in the yeast system, with caffeic acid, 9, having little to no effect. Antifungal activity levels against A. flavus were similar. This similarity in antifungal activity demonstrated the usefulness of the S. cerevisiae bioassay for screening antifungal compounds. Assays using deletion mutants of yeast identified signal transduction and antioxidative stress response genes important to fungal tolerance. Targeting the antioxidative stress response system with certain compounds (e.g., 4) in combination with strobilurin fungicides had a synergistic effect against both fungi.

Effectiveness of pulsed light treatment for degradation and detoxification of aflatoxin B1 and B2 in rough rice and rice bran

“…This strain only produces AFB 1 and AFB 2 . A. flavus was grown in potato dextrose agar (PDA) (Sigma, St. Louis, MO, USA) at 28 C for 7 days (Kim, Campbell, Mahoney, Chan, & Molyneux, 2004). A conidial suspension of 10 5 cfu/mL was prepared by flooding the culture plates with 0.03% Tween 80 (w/w) (Wang et al, 2014).…”

Natural Products as Tools for Chemogenomic Analysis of Mycotoxin Biosynthesis and Fungal Stress-Response Systems

“…Bioassays involving gene deletion mutants of the yeast, Saccharomyces cerevisiae, as a model fungus, show that gallic acid acts as a potent antioxidant. These findings suggest there is an association between oxidative stress and aflatoxigenesis in A. flavus (3).…”

“…), which, in turn, may subdue signaling in pathways involved in oxidative stress responses. For example, methyl gállate inhibits aflatoxin biosynthesis (2) and also inhibits peroxide-induced oxidative stress in yeast (3). This compound was recently found to directly inhibit cyclooxygenase-2 (COX-2), an enzyme involved in lipid hydroperoxide formation (20).…”

Antimicrobial phenylpropanoids from the Argentinean highland plant Parastrephia lucida (Meyen) Cabrera

“…The effect found in the subfraction IV suggests synergism with other constituents. Cinnamic acids have been found to display better antifungal effects than coumaric acids (Kim et al, 2004). Transcinnamic acid was found to increase the activity of various antibiotic drugs against Mycobacterium avium.…”