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United States Department of Agriculture

Agricultural Research Service

Title: Structure/activity Studies of Some Inhibitiors of A. Flavus Aflatoxin B1 Synthesis Which Occur in Corn Kernels

item Norton, Robert

Submitted to: Aflatoxin Elimination Workshop Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: October 29, 1996
Publication Date: N/A

Technical Abstract: This work evaluated metabolites of corn and related compounds for their effect on growth and aflatoxin B1 (AFB1) production by Aspergillus flavus NRRL 3357 and determined how representative NRRL 3357 was as a test strain. The suspended disc culture method (RA Norton, 1995, Mycopath. 129:103-109) was used in evaluating the compounds discussed. Anthocyanin aglycones were tested and compounds lacking a hydroxy group at the 3-position of the heterocyclic ring were significantly less inhibitory than 3-hydroxy compounds. Tests with other flavonoids showed that a double bond at the 2-position was essential for activity. For carotenoids, highest inhibition correlated with the presence of an alpha-ionone type ring structure. Ring keto groups at the 4,4' position decreased activity as did terminal aldehyde and carboxylic acid groups. Use of A. parasiticus mutant SRRC 164 showed that alpha-carotene and delphinidin showed no accumulation of intermediates in the aflatoxin biosynthetic pathway and inhibited AFB1 and norsolorinic acid about equally, indicating that inhibition occurs early in the pathway for these two compounds. Aflatoxin B1 inhibitors were tested pairwise to determine if interference in inhibition would occur. No interference was found. Various A. flavus and A. parasiticus strains were tested against beta-carotene. A. flavus strains had from 89% to 96% inhibition and were significantly more sensitive than NRRL 3357 which averages about 50% inhibition. A. parasiticus strains were less sensitive and generally similar in inhibition to NRRL 3357.

Last Modified: 4/21/2015
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