Recent developments in stable isotope dilution assays in mycotoxin analysis with special regard to Alternaria toxins

Abstract

Stable isotope dilution assays (SIDAs) are becoming ever commoner in mycotoxin analysis, and the number of synthesized or commercially available isotopically labelled compounds has greatly increased in the 7 years since our last review dealing with this topic. Thus, this review is conceived as an update for new applications or improvements of SIDAs for compounds discussed earlier, but the main focus is on newly introduced labelled substances and the development of SIDAs for, for example, fusarin C, moniliformin or the enniatins. Mycotoxin research has concentrated on the emerging group of Alternaria toxins in recent years, and a series of SIDAs have been developed, including ones for tenuazonic acid, alternariol, altertoxins and tentoxin that are discussed in detail in this review. Information about synthetic routes, isotopic purity and mass-spectrometric characterization of labelled compounds is given, as well as about the development and validation of SIDAs and their application to foods, feeds or biological samples. As the number of commercially available labelled standards is increasing continuously, a general tendency for the use of analytical methods based on liquid chromatography coupled with mass spectrometry capable of identifying a series of mycotoxins simultaneously ("multimethods") and using one or more labelled internal standards can be observed. An overview of these applications is given, thus demonstrating that SIDAs are increasingly being used in routine analysis.

AlternariaMycotoxins in Food and Feed: An Overview

“…ALT has shown high acute toxicity with a LD 50 value of 50 mg/kg bw in mice, whereas TeA is considered to be the most acutely toxic among the Alternaria mycotoxins [27]. TeA is known to occur in high concentrations in commodities and has attracted increasing attention in recent years [11]. It inhibits protein biosynthesis at the ribosomal level in mammalian cells by suppressing the release of newly formed proteins from the ribosomes and is biologically active as it exerts cytotoxic, phytotoxic, antitumor, antiviral, antibiotic, and antibacterial effects [28].…”

“…but are considered to be very critical because of their mutagenic properties [34]. Because of the lack of available reference compounds, in particular for ATXs, analytical studies remain less common [11]. ATXs have been reported to be highly potent mutagens and more acutely toxic to mice than AOH and AME and cause DNA strand breaks.…”

“…All three compounds are considered to be phytotoxins, with TEN being the most potent, inhibiting photophosphorylation and inducing chlorosis. However, no toxicological data are available for mammals, and the data on the occurrence of this toxin in food and feed are limited as well [11].…”

“…In this sense, mycotoxin research has focused in recent years on the emerging group, along with the major Alternaria toxins [11]. Emerging Alternaria mycotoxins mainly belong to five chemical classes: pyranones or benzopyrones (altenuene (ALT); altenuisol (AS); altenusin (ALN)), amine/amide metabolites (tenuazonic acid (TeA); altersetin (ALS)), perylenequinones (altertoxins (ATXs), alterperylenol or alteichin (ALTCH), and stemphyltoxin (STE)), and anthraquinones (Macrosporin A, Altersolanol (As-A)).…”

Tracking emerging mycotoxins in food: development of an LC-MS/MS method for free and modified Alternaria toxins

“…Using solid-phase extraction, LODs between 0.1 and 0.6 ng/mL were achieved for 12 Alternaria toxins in wine and fruit and vegetable juices [5]. Isotopically labeled internal standards can be used to ensure the performance of quantitative methods and were employed in first applications [30, 35, 36]. The most frequently analyzed food matrices were cereal- and tomato-based products, fruit juices, wine, maize, and sunflower seeds [4, 20, 26, 27, 29, 31–34, 37–40].…”