Identification of six new Alternaria sulfoconjugated metabolites by high-resolution neutral loss filtering

Megan J Kelman; Justin B Renaud; Keith A Seifert; Jonathan Mack; Kumaran Sivagnanam; Ken K-C Yeung; Mark W Sumarah

doi:10.1002/rcm.7286

Identification of six new Alternaria sulfoconjugated metabolites by high-resolution neutral loss filtering

Rapid Commun Mass Spectrom. 2015 Oct 15;29(19):1805-10. doi: 10.1002/rcm.7286.

Authors

Megan J Kelman^{1

2}, Justin B Renaud¹, Keith A Seifert³, Jonathan Mack³, Kumaran Sivagnanam⁴, Ken K-C Yeung^{2

5}, Mark W Sumarah^{1

2}

Affiliations

¹ Southern Crop Protection and Food Research Centre, Agriculture and Agri-Food Canada, London, ON, N5V 4T3, Canada.
² Department of Chemistry, University of Western Ontario, London, ON, N6A 5B7, Canada.
³ Eastern Cereal and Oilseed Research Centre, Agriculture and Agri-Food Canada, Ottawa, ON, K1A 0C6, Canada.
⁴ Canadian Grain Commission, Grain Research Laboratory, Winnipeg, MB, R3C 3G8, Canada.
⁵ Department of Biochemistry, University of Western Ontario, London, ON, N6A 5C1, Canada.

PMID: 26331931
DOI: 10.1002/rcm.7286

Abstract

Rationale: Many species of Alternaria damage important agricultural crops, including small grains and tomatoes. These fungi can produce a variety of secondary metabolites, some of which are toxic to humans and animals. Interest in screening for conjugated or 'modified' mycotoxins has increased because of their tendency to evade traditional analytical screening methods. Two sulfoconjugated Alternaria toxins have been reported and the potential exists for many more.

Methods: One hundred and forty-eight Canadian strains of Alternaria spp., about half of them isolated from grain, were grown on Potato Dextrose Agar in Petri dishes for 7 days. Plugs of each strain were removed, extracted and screened by a rapid liquid chromatography (LC)/data-dependent tandem mass spectrometry (MS(2)) method in negative electrospray ionization mode. Data generated on an Orbitrap Q-Exactive mass spectrometer was processed by post-acquisition neutral loss filtering (NLF). Seven isolates that produced sulfoconjugates of known Alternaria toxins were selected for growth on three additional types of fermentation media.

Results: Collision-induced dissociation of sulfoconjugated ions displayed a distinctive neutral loss of SO3 (79.957 Da) that was detected in the MS(2) datasets using post-acquisition NLF. A total of 108 of the 148 isolates screened produced sulfoconjugated metabolites on agar plates. Analysis of the seven isolates grown in liquid culture, on rice and Cheerios, led to the discovery of six new, two previously reported and 30 unidentified sulfoconjugated compounds.

Conclusions: NLF of HRMS(2) data from an Orbitrap Q-Exactive is a powerful tool for the rapid discovery of sulfoconjugated fungal metabolites. This technique could also be applied to the detection of other important conjugated mycotoxins such as glucosides. The majority of the Canadian isolates of Alternaria spp. studied produced sulfoconjugated metabolites, some of which had no known 'free' Alternaria precursor metabolite, indicating that they are possibly new metabolites. The advantage of sulfoconjugation to Alternaria spp. is unknown, and warrants further study into the mechanisms behind the sulfur assimilatory pathways.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Alternaria / chemistry
Alternaria / isolation & purification
Alternaria / metabolism*
Chromatography, Liquid
Edible Grain / microbiology*
Metabolome
Spectrometry, Mass, Electrospray Ionization / methods
Sulfur Compounds / analysis*
Sulfur Compounds / chemistry
Sulfur Compounds / isolation & purification*
Sulfur Compounds / metabolism

Substances

Sulfur Compounds