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Detection and Quantitative Analysis of the Non-cytotoxic allo-Tenuazonic Acid in Tomato Products by Stable Isotope Dilution HPLC-MS/MS
journal contribution
posted on 2015-12-23, 00:00 authored by Sebastian Hickert, Isabel Krug, Benedikt Cramer, Hans-Ulrich HumpfTenuazonic
acid (1) is a mycotoxin produced mainly
by fungi of the genus Alternaria. It occurs in a
variety of agricultural products. allo-Tenuazonic
acid (2) is an isomer of 1 that is not chromatographically
separated from 1 in most analytical methods. Therefore,
both isomers are quantitated as a sum parameter. In this study a QuEChERS
(quick, easy, cheap, effective, rugged and safe) based stable isotope
dilution HPLC-MS/MS method including the chromatographic separation
of both isomers was developed and applied to 20 tomato products from
the German market. All products showed contamination with both toxins. 1 was found in a range from 5.3 ± 0.1 to 550 ± 15
μg/kg (average = 120 μg/kg) and 2 in a range
from 1.5 ± 0.4– to 270 ± 0.8 μg/kg (average
= 58 μg/kg). 2 represents 7.0–44% of the
sum of both isomers (average = 29%). This is the first reported occurrence
of 2 in food samples. To evaluate and compare the cytotoxicities
of 1 and 2, both compounds were isolated
from a synthetic racemic mixture. 1 showed moderate cytotoxic
effects on HT-29 cells starting at 100 μM, whereas 2 exhibited no activity. 2 was not produced in liquid
cultures of Alternaria alternata in
yeast extract sucrose (YES) medium, but could be detected in small
amounts in tomato puree inoculated with the fungus.