Location: Food and Feed Safety ResearchTitle: Identification of novel metabolites from Aspergillus flavus by high resolution and multiple stage mass spectrometry Author
|Vanden Bussche, Julie|
|Diana Di Mavungu, Jose|
|De Saeger, Sarah|
Submitted to: Food Additives & Contaminants
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/25/2013
Publication Date: 1/9/2014
Publication URL: http://handle.nal.usda.gov/10113/58361
Citation: Malysheva, S.V., Arroyo-Manzanares, N., Cary, J.W., Ehrlich, K., Vanden Bussche, J., Vanhaecke, L., Bhatnagar, D., Diana Di Mavungu, J., De Saeger, S. 2014. Identification of novel metabolites from Aspergillus flavus by high resolution and multiple stage mass spectrometry. Food Additives & Contaminants. Part A, 31(1):111-120. doi: 10.1080/19440049.2013-859743. Interpretive Summary: Aspergillus flavus is a mold that is a common contaminant of cotton, corn, and peanuts. Because of its ability to produce the extremely toxic and cancer causing compounds, the aflatoxins, it can be a serious problem for food and feed safety. Although strategies to reduce aflatoxins in foods has been the main concern of this research, we now find that A. flavus produces metabolites in sclerotia that are of interest because of their ability to form sclerotial pigments that help stabilize the stability of the sclerotia in soil. The soil in agricultural fields is the source of the contamination that occurs in the cotton, corn, and peanut seeds. Using a highly accurate analytical method that utilizes mass spectrometry, a new metabolite has been identified that is a likely source of the sclerotial pigments of A. flavus. This metabolite is formed by a polyketide synthase enzyme that is related to the same type of enzyme that is needed for formation of the aflatoxins.
Technical Abstract: Aspergillus flavus contains more than 55 gene clusters which are predicted to encode proteins involved in secondary metabolite production. One of these, cluster 27, contains a polyketide synthase (pks27) gene which encodes a protein that is highly homologous to the aflatoxin cluster PKS. Comparative metabolomics, using ultra-high performance liquid chromatography coupled to high resolution Orbitrap mass spectrometry (MS) was used to detect metabolites differentially expressed in the A. flavus wild-type and 'pks27 mutant strains. Metabolite profiling was aided by a statistical differential analysis of MS data using SIEVE software. This differential analysis combined with accurate mass data from the Orbitrap and ion trap multiple stage MS allowed us to identify four metabolites produced only by the wild-type culture. These include asparasone A (358 Da), an anthraquinone pigment, and related anthraquinones with masses of 316, 340, and 374 Da. These latter three compounds had similar fragmentation patterns to that of asparasone A. The 316 Da anthraquinone is particularly interesting because it is most likely formed by incorporation of 7 malonyl-CoA units rather than the 8 units required for formation of asparasone A. The 340 Da and 374 Da metabolites are the dehydration, and an oxy-derivative of asparasone A, respectively. Asparasone A was also identified in extracts from several other Aspergillus species.