Determination of tenuazonic acid in human urine by means of a stable isotope dilution assay

Abstract

The content of tenuazonic acid in human urine was determined by a stable isotope dilution assay (SIDA) that was recently developed for the analysis of food commodities and extensively revalidated for urine matrix in this study. Linearity of the response curve was proven between molar ratios n(labeled standard)/n(analyte) of 0.02-100. The limit of detection (LOD) and the limit of determination (LOQ) were 0.2 µg/L and 0.6 µg/L, respectively. The mean recovery of the stable isotope dilution assay was 102 ± 3 % in the range between 1.0-100 µg/L. Interassay precision was 6.7 % (relative standard deviation of three triplicate analyses of a human urine sample during three weeks). The method was applied to two studies dealing with urinary excretion of tenuazonic acid: In the first study, tenuazonic acid was quantified in the 24-hour urine of six volunteers from Germany (3 female, 3 male) in a concentration range of 1.3-17.3 µg/L or 2.3-10.3 ng/mg-1 creatinine, respectively. In the second study, two volunteers (1 female, 1 male) ingested 30 µg tenuazonic acid by consumption of naturally contaminated whole meal sorghum infant cereals and tomato juice, respectively. The urinary excretion of the ingested tenuazonic acid was 54-81 % after six hours, depending on matrix and volunteer. After 24 hours 87-93 % of the ingested amount of tenuazonic acid was excreted, but the fate of the remaining about 10 % is open. Thus, it is not possible to exclude potential health hazards for the consumer, completely.

AlternariaMycotoxins in Food and Feed: An Overview

“…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]. TeA toxicity has been reported in chick embryos and several animal species, including guinea pigs, mice, rabbits, dogs, and rhesus monkeys [29].…”

“…Concerning human exposure, the presence of TeA in the urine of six human volunteers in concentrations ranging from 1.3 to 17.3 g/L was reported. It was observed that 87-93% of orally consumed TeA was excreted as parent compound into the urine of two human volunteers within 24 h after ingestion [28].…”

Occurrence of Alternaria toxins in food products in The Netherlands

“…Unfortunately, this approach cannot be used when mass spectrometric detection is applied. The derivation of TeA with 4-dinitrophenylhydrazine (DNPH) (Siegel et al, 2009) and the use of stable isotope dilution assay (SIDA) with the addition of [ 13 C, 15 N]-TeA as internal standard (Stefan Asam et al, 2011) have significantly improved the analysis and allowed the determination of TeA in flour, bakery products and beer (Stefan Asam, Habler, & Rychlik, 2013;Stefan Asam & Rychlik, 2013;Siegel, Merkel, Koch, & Nehls, 2010). The main drawback of these methods, as opposed to the dilute-and-shoot methods, is that they do not allow the simultaneous determination of the other four Alternaria toxins, they are more time-consuming and more laborious.…”

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

“…In toxicokinetic studies in humans, the content of TA in human urine was determined by a SIDA extensively revalidated for urine matrix [60]. It was very difficult to obtain blank urine samples as TA is constantly consumed because of its ubiquitous occurrence.…”