|Kim, Jong Heon|
|Chan, Kathleen - Kathy|
|Haff, Ronald - Ron|
Submitted to: Frontiers in Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/18/2014
Publication Date: 3/7/2014
Publication URL: http://handle.nal.usda.gov/10113/58725
Citation: Kim, J.H., Mahoney, N.E., Chan, K.L., Campbell, B.C., Haff, R.P., Stanker, L.H. 2014. Use of benzo anologs to enhance antimycotic activity of kresoxim methyl for control of aflatoxigenic fungal pathogens. Frontiers in Microbiology. DOI: 10.3389/fmicb.2014.00087. Interpretive Summary: Controlling fungi that produce hepato-carcinogenic aflatoxins in crops is problematic as effective commercial fungicides for treating aflatoxin-producing fungi are very limited. A very low level of aflatoxin contamination can have a perniciously negative effect on food safety and economic value of a number of crops. Also, development of fungal resistance to conventional antifungal agents is a global agricultural issue. Therefore, effective methods are continually needed for control of aflatoxigenic fungal pathogens. In this study, we showed that application of safe benzo derivatives, such as octylgallate, could lower the effective dosage of the fungicide strobilurin when co-applied. In addition to the antioxidant system, octylgallate negatively affects fungal cell wall integrity, resulting in target-based inhibition of fungal pathogens. Octylgallate also has moderate antiaflatoxigenic activity. Thus, the method we developed, antifungal chemosensitization, renders treatment or agricultural practices for control of aflatoxin-producing fungi less expensive and safer.
Technical Abstract: Potentiation of the conventional fungicide, strobilurin, was achieved by octylgallate-mediated chemosensitization. Octylgallate exhibited considerably higher antifungal activity compared to veratraldehyde. Octylgallate in concert with the fungicide, strobilurin (kresoxim methyl), greatly enhanced sensitivity of aflatoxin-producing Aspergillus strains to this fungicide. The combination with octylgallate also overcame the tolerance of A. fumigatus stress signaling mutants to strobilurin. The degree of compound interaction resulting from chemosensitization of the fungi by octylgallate was determined, where synergistic activity greatly lowered minimum inhibitory concentrations or minimum fungicidal concentrations of compounds. The level of antifungal or chemosensitizing activity was also compound-strain specific, indicating differential susceptibility of tested strains to antifungal treatments. Besides targeting the antioxidant system, octylgallate also negatively affected the cell wall-integrity pathway. We concluded that certain benzo analogs, such as octylgallate, effectively inhibit fungal growth. They possess chemosensitizing capability to increase efficacy of strobilurin, and thus could reduce effective dosages of this fungicide and alleviate negative side effects associated with current antifungal practices. Octylgallate also exhibited moderate antiaflatoxigenic activity.