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. 2025 Aug;17(8):1357-1367.
doi: 10.1002/dta.3820. Epub 2024 Dec 18.

Further Investigation Into an Environmental Source for Aminorex

Lydia Brooks  1 , Michael Ryan  1 , Erin McCosham  1 , Devan Loganathan  2
Affiliations

Further Investigation Into an Environmental Source for Aminorex

Lydia Brooks et al. Drug Test Anal. 2025 Aug.

Abstract

In 2009, levamisole was identified as a source for several aminorex positives reported in postrace equine samples in Canada. Since then, unexplained detections of aminorex continue to be identified in equine samples where there is no evidence to link these detections to a levamisole administration. Previous studies identified a compound named barbarin in some species of plants from the Brassicaceae family and suggested that barbarin may be a possible precursor for aminorex. The objectives of this study were to (1) investigate the link between barbarin and aminorex and (2) identify other biomarkers of plant origin. Methods were developed and validated for the detection of aminorex, barbarin, glucobarbarin, and other associated compounds. Aminorex was administered to one horse, and barbarin was not detected in any plasma and urine samples. Barbarea stricta and Barbarea orthoceras were administered to two horses, and aminorex was detected in all plasma and urine samples collected. Barbarin was detected in some plasma but not in urine samples. Resedine was observed in retrospective examination of chromatograms of the plant material and from all plants postadministration plasma and urine samples from the two horses. Resedine was administered to one horse and was detected in plasma and urine samples, but aminorex was only detected in urine samples. These results provide evidence that resedine is an intermediary compound between barbarin and aminorex in horses and that resedine can be used as a biomarker to eliminate the reporting of aminorex positives originating from the ingestion of plants from the Brassicaceae family.

Keywords: HPLC/HRAM; aminorex; barbarin; glucobarbarin; resedine.

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Conflict of interest statement

The authors declare no conflicts of interest.

Figures

FIGURE 1
FIGURE 1
Aminorex (left), barbarin (center), and resedine (right).
FIGURE 2
FIGURE 2
Enzymatic conversion of barbarin (R1‐H R2‐Ph) to resedine (R1‐H R2‐Ph).
FIGURE 3
FIGURE 3
Detection of barbarin in the plant material SM 1793 Barbarea stricta .
FIGURE 4
FIGURE 4
Detection of aminorex in the plasma following an administration of Barbarea orthoceras .
FIGURE 5
FIGURE 5
Detection of aminorex in the urine following the administration of Barbarea stricta to a horse.
FIGURE 6
FIGURE 6
Detection of barbarin in the plasma of a horse following the administration of Barbarea orthoceras .
FIGURE 7
FIGURE 7
Biochemical conversion of glucobarbarin into barbarin via an unstable isothiocyanate and a further conversion to resedine. Source: Agerbirk et al. [6].
FIGURE 8
FIGURE 8
Detection of resedine in the urine of a horse after the administration of Barbarea stricta .
See this image and copyright information in PMC

References

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