Photochemical trans-/cis-Isomerization and Quantitation of Zearalenone in Edible Oils

Abstract

The emphasis of the present work was to investigate the photochemical conversion of trans- to cis-zearalenone in edible oils under real-life conditions. For quantitation purposes a cis-zearalenone standard was synthesized and characterized for its identity and purity (≥95%) by (1)H NMR, X-ray crystallography, HPLC fluorescence and mass spectrometric detection. In a sample survey of 12 edible oils (9 corn oils, 3 hempseed oils) from local supermarkets all corn oils contained trans-zearalenone (median 194 μg/kg), but no cis-zearalenone was detected. For alteration studies trans-zearalenone contaminated corn oils were exposed to sunlight over 4 and 30 weeks, revealing an obvious shift toward cis-zearalenone up to a cis/trans ratio of 9:1 by storage in colorless glass bottles. Irradiation experiments of trans-zearalenone in different organic solvents confirmed the preferred formation of cis-zearalenone possibly caused by entropic effects rather than by enthalpic entities as investigated by quantum chemical and classical force field simulations.

In Vitro Phase I Metabolism of cis-Zearalenone

“…The maximum cis-ZEL formation was observed after 24 h for α-trans-ZEL and after 48 h for β-trans-ZEL. Irradiation in ethyl acetate yielded the highest cis-/trans-ZEL ratio (α-ZEL, 3.5; β-ZEL, 3.6) when compared to heptane, acetonitrile, acetone, and methanol, confirming the results of Koppen et al 19 for ZEN isomerization.…”

“…Native cis-ZEN was generated photochemically from trans-ZEN by a procedure reported earlier. 19 In summary, native trans-ZEN is dissolved in ethyl acetate and irradiated by UV-light (λ = 350 nm) for 8 h. The irradiated solution is then subjected to preparative HPLC in order to separate the trans from the cis isomer and to obtain pure native cis-ZEN. U-[ 13 C 18 ]-cis-ZEN was synthesized as described earlier following the same procedure as that for the preparation of native cis-ZEN.…”

Hazard identification of cis/trans -zearalenone through the looking-glass

“…The cis-isomer has been described in edible oils, raw grains and products thereof, especially wet ground maize for feeding. Isomerization occurs at high extent under sunlight, but the cis-trans ratio may largely vary on account of the environmental conditions (Brezina et al, 2013;K€ oppen et al, 2012). Due to analytical limitation, data about their incidence are scarce and a preliminary risk assessment study has never been done.…”

Electrochemical simulation of biotransformation reactions of citrinin and dihydroergocristine compared to UV irradiation and Fenton-like reaction

“…Degradation of organic pollutants is also achieved by using photocatalytic techniques. Photodegradation experiments have been performed with mycotoxins to decontaminate apple juice or red wine from mycotoxins or isomerization [11][12][13].…”