Aminorex identified in horse urine following consumption of Barbarea vulgaris; a preliminary report

Abstract

BackgroundAminorex, (RS)-5- Phenyl-4,5-dihydro-1,3-oxazol-2-amine, is an amphetamine-like anorectic and in the United States a Drug Enforcement Administration [DEA] Schedule 1 controlled substance. Aminorex in horse urine is usually present as a metabolite of Levamisole, an equine anthelmintic and immune stimulant. Recently, Aminorex identifications have been reported in horse urine with no history or evidence of Levamisole administration. Analysis of the urine samples suggested a botanical source, directing attention to the Brassicaceae plant family, with their contained GlucoBarbarin and Barbarin as possible sources of Aminorex. Since horsepersons face up to a 1 year suspension and a $10,000.00 fine for an Aminorex identification, the existence of natural sources of Aminorex precursors in equine feedstuffs is of importance to both individual horsepersons and the industry worldwide.ResultsTesting the hypothesis that Brassicaceae plants could give rise to Aminorex identifications in equine urine we botanically identified and harvested flowering Kentucky Barbarea vulgaris, (“Yellow Rocket”) in May 2018 in Kentucky and administered the plant orally to two horses. Analysis of post-administration urine samples yielded Aminorex, showing that consumption of Kentucky Barbarea vulgaris can give rise to Aminorex identifications in equine urine.ConclusionsAminorex has been identified in post administration urine samples from horses fed freshly harvested flowering Kentucky Barbarea vulgaris, colloquially “Yellow Rocket”. These identifications are consistent with occasional low concentration identifications of Aminorex in equine samples submitted for drug testing. The source of these Aminorex identifications is believed to be the chemically related Barbarin, found as its precursor GlucoBarbarin in Kentucky Barbarea vulgaris and related Brassicaceae plants worldwide.

The medication violations in racehorses at Louisiana racetracks from 2016 to 2020

“…However, a recent study reported identification of aminorex in horse urine with no history or evidence of levamisole administration. Analysis of the horse urine samples in this study suggested a botanical source directing attention to the Brassicaceae plant family as possible sources of aminorex (Maylin et al., 2019 ).…”

Synthesis and characterization of d5‐barbarin for use in barbarin‐related research

“…Structural damage in these plants triggers hydrolysis of glucobarbarin by myrosinase to an intermediate which spontaneously cyclizes to barbarin, Figure 2, which then functions as an insect repellant or attractant 8 . As set forth above, barbarin is related structurally to aminorex, and consumption of Brassicaceae plant fragments in equine feed is therefore a possible source of unexplained aminorex identifications, as demonstrated in our recently published research 9 …”

“…8 As set forth above, barbarin is related structurally to aminorex, and consumption of Brassicaceae plant fragments in equine feed is therefore a possible source of unexplained aminorex identifications, as demonstrated in our recently published research. 9 While this equine administration research 9 links consumption of the Brassicaceae plant Barbarea vulgaris to urinary aminorex identifications, it does not unequivocally identify barbarin as the proximate chemical source of these identifications. To address this matter, we have streamlined the synthesis, purified, and characterized d 5 -barbarin, the availability of which will allow more definitive identification of the relationship between plant barbarin and equine consumption of such plant material being associated with equine aminorex identifications.…”

Synthesis and characterization of barbarin, a possible source of unexplained aminorex identifications in forensic science

“…The experimental horses declined consumption when offered the dried plant materials, but readily consumed the plant material when mixed with sweet feed. Then, 4 hours post consumption of Barbarea vulgaris the presence of aminorex was shown in their urine samples with no evidence for the presence of barbarin in the same urine 15 …”