The Impact of Storage Temperature and Time on Ergot Alkaloid Concentrations

Abstract

Ergot sclerotia produce toxic secondary metabolites, ergot alkaloids, that infect cereal crops and grasses. Ergot alkaloids have two isomeric configurations: the C-8-R-isomer (R-epimer), and the C-8-S-isomer (S-epimer). Ergot contaminated matrices, such as cereal grains or grasses, may be stored for extended periods at various temperatures before being analyzed, utilized, or consumed. This study assessed the concentration of six common ergot alkaloids in both configurations found in naturally contaminated wheat over time (one, two, and four months) at different temperatures (room temperature, +4 °C, and -20 °C) using ultra-high-performance liquid chromatography-tandem mass spectrometry. The data indicate that the total ergot concentration within a natural contaminated sample varies over time at room temperature, +4 °C, and -20 °C. The total ergot concentration increased until month two, and decreased at month four, independent of temperature (p < 0.05). The total R-epimer concentration appeared to be less stable over time than the total S-epimer concentration. The changes in the total R and total S-epimer concentrations may have been caused by changes in the ergocristine and ergocristinine concentrations, respectively. Time and temperature should be considered when storing potentially contaminated matrices in a laboratory or practical agriculture situations. Quantification of ergot contaminated matrices should occur prior to their use to ensure the most reliable estimates of the concentration of ergot.

Keywords: contamination; epimer; grain.

Figure 1

The total (six R and six S-epimers) ergot concentration (µg/kg) in natural ergot-contaminated hard red spring wheat over time (month) at (A) room temperature (RT), (B) +4 °C, and (C) −20 °C, analyzed utilizing high-performance liquid chromatography–tandem mass spectrometry. [Box-plot: whiskers are defined at the minimum and maximum values, top of box is defined as the 75th percentile, bottom of box is 25th percentile, and middle line is defined at the median. The ° are defined as outliers (>1.5 × interquartile range) and the * are defined as an extreme outlier (>3 × interquartile range)]. All outliers were included in the statistical analysis. Different lowercase letters represent statistical differences between each time period at each temperature (p < 0.05, generalized estimating equation, pairwise comparison with sequential Sidak correction, n = 6/temperature and time.

Figure 2

The concentration (µg/kg) of the total R-epimers and total S-epimers in natural ergot-contaminated hard red spring wheat over time (month) at (A) room temperature (RT), (B) +4 °C, and (C) −20 °C, analyzed utilizing high-performance liquid chromatography–tandem mass spectrometry. [Box-plot: whiskers are defined at the minimum and maximum values, top of box is defined as the 75th percentile, bottom of box is 25th percentile, and middle line is defined at the median. The ° are defined as outliers (>1.5 × interquartile range) and the * are defined as an extreme outlier (>3 × interquartile range)]. All outliers were included in the statistical analysis. Different lowercase letters represent statistical differences between each time period at each temperature for either the total R-epimers (a–c) or total S-epimers (d–f) (p < 0.05, generalized estimating equation, pairwise comparison with sequential Sidak correction, n = 6/temperature and time for each epimer.

Figure 3

The concentrations (µg/kg) of ergocristine and ergocristinine in natural ergot-contaminated hard red spring wheat over time (month) at (A) room temperature (RT), (B) +4 °C, and (C) −20 °C, analyzed utilizing high-performance liquid chromatography–tandem mass spectrometry. [Box-plot: whiskers are defined at the minimum and maximum values, top of box is defined as the 75th percentile, bottom of box is 25th percentile and middle line is defined at the median. The ° are defined as outliers (>1.5 × interquartile range) and the * are defined as an extreme outlier (>3 × interquartile range)]. All outliers were included in the statistical analysis. Different lowercase letters represent statistical differences between each time period at each temperature for ergocristine (a–c) or ergocristinine (d–g) (p < 0.05, generalized estimating equation, pairwise comparison with sequential Sidak correction, n = 6/temperature and time for each epimer.